ALBERT

Description: SUMMARYThree hundred and seventy-six isolates, or about 9% of the cultures collected in 1967 and 1968 from soil of permanent pasture, that, prior to 1883, supported mixed conifer and deciduous forest, were cultivated in the laboratory. Antibiotic production was detected in 27% of the cultures. Similarly, 329 isolates, or 9% of those collected in the same period from soil of permanent pasture reclaimed from tidal marsh, were grown in the laboratory and antibiotics detected in 30%. The forest soil, because it was already known to have a denser fungal population, thus had a greater antibiotic production potential than the marshland soil. There was a small increase in the number of isolates from the forest soil that produced antibiotics when those obtained in the spring were compared to those collected in the autumn. The opposite relationship was found when the marshland isolates from the two seasons were similarly compared. The results are consistent with the hypothesis that the fungal populations of these soils are a parameter in the aetiology of the ill-thrift that is found in ruminants at Nappan, Nova Scotia.

Description: SUMMARYMacro-organic matter (roots and partially decomposed plant debris retained on a 0·25 mm mesh sieve) was measured in soils under various swards. Under a grazed perennial ryegrass/white clover sward, sown on arable land, macro-organic matter in the top 15 cm of soil rose steadily in the first 8 years to 15·8 t/ha, but subsequently declined. Under arable cropping there was great variation with crop and season. Under grass, most of the macro-organic matter accumulated in the top 2 cm of soil, particularly during the first 3 or 4 years. More macro-organic matter was found under perennial ryegrass/white clover than under cocksfoot/white clover swards.After 3 years under grass macro-organic matter accounted for 10% of the total soil carbon, and represented about half the increase in soil carbon.Half, or less, of the nitrogen which accumulated in soil under grass was in the macroorganic matter fraction. The differences between swards which received no N fertilizer and those which received 940 kg/ha over 3 years was small, 16–40 kg N/ha respectively for cut and frequently grazed swards. The ratio of C:N in macro-organic matter under different swards averaged 22:1.

Description: SUMMARYSoluble ammonium nitrate (AN) and urea were compared with slow-release oxamide and sulphur-coated urea (SCU) as N sources for clipped annual ryegrass (Lolium multiflorum) or common bermuda grass (Cynodon dactylon) in four greenhouse experiments. Mixed and surface applications of a wide range of N rates were evaluated for 9 to 14 cuttings of grass forage. Both granular oxamide and SCU exhibited slow-release N properties, especially when surface-applied. Uptake distribution of N with high application rates of AN and urea tended to resemble that with the slow-release sources. Slow-release properties of oxamide and SCU were accentuated at high application rates. Lower N recovery from surface-applied urea than from AN indicated volatilization loss of urea N. Volatilization loss also occurred with oxamide, but low N recovery from oxamide and SCU resulted largely from incomplete dissolution of the granules during the 18- to 34-week experimental periods. Very low N recovery was obtained from urea formaldehyde having an activity index of 42.

Description: SUMMARY1. The Awassi ewes reached an average live weight of 45 kg at two years of age and a mature weight of 57 kg at four years of age.2. The average yearly production of grease wool has been 2·2 kg.3. When rams were kept with the flock throughout the year approximately 60% of the lambings occurred during January–February. It declined rapidly during the following months and no lambs were born in July–August.4. Single lambs had an average birth weight of 4·6 kg for males and 4·3 for females. Twin lambs were about 20% lighter than singles. The corresponding weaning weight at two months of age was 17·9 and 16·8 for singles and 13·4 and 12·4 for twins.5. The twinning rate increased from 5% at first lambing to 30–35% at 6th lambing, when the ewes were about seven years old.

Description: SUMMARYMerino lambs had higher serum protein concentrations at birth than Blackface lambs. In both breeds single lambs had higher concentrations than twins. The maximum mean immunoglobulin concentrations in Merino singles, Blackface singles and Blackface twins were 2·50±0·12, 2·50±0·19 and l·96±0·15 g/100 ml serum respectively, and were recorded 18 or 21 h after birth.

Description: SUMMARYAn experiment was conducted using 36 Hereford × Shorthorn bullocks of about 350 kg initial live weight. Winter planes of nutrition 13 December to 23 March were ‘low’ (hay only) and ‘medium’ (hay plus 1·8 kg concentrate); the former group of 18 bullocks lost on average 21·5 kg while the latter gained 26·5 kg. Each group was then stocked at 2·5 (low), 4·3 (medium) and 6·2 (high) bullocks per hectare and rotationally grazed on 10 plots, 7 of which contained H.I.-white clover mixture and the remaining 3 contained permanent pasture. Pasture digestibility and intake were determined for 16 weekly periods between early April and the end of September. Organic matter digestibility (OMD) of grazed herbage was determined in vitro on samples obtained by means of two rumen-fistulated bullocks. One gelatin capsule containing about 10 g of chromic oxide was daily administered to each bullock to estimate organic matter output. Winter feeding planes had no significant effect on OMD, and increasing the stocking rate increased herbage OMD only during the final 6 weeks. Significantly more organic matter was ingested during the grazing season by animals which had previously been fed on a low plane of nutrition. Stocking rates also significantly affected OMI. Bullocks fed on a low plane during winter were slightly more efficient subsequently in converting herbage into live-weight gain but this was a reflection of their lower average body weight; when feed efficiency was expressed on the basis of metabolic size, bullocks fed on a medium plane were more efficient in converting feed to live-weight gain. It is concluded that the higher daily gains on pasture of bullocks previously fed on a low plane is largely the result of a significantly higher feed intake by these animals.

Description: SUMMARYAn experiment is described which investigated for a period of 12 years the effects of four methods of basic cultivation – ploughing, rotary cultivating, cultivating and discing – on crop yields in a four-course rotation of winter wheat, sugar beet, spring barley followed by either potatoes (on one half of each main plot) or ley (on the other). The cultivations were carried out at two different times and each crop was grown at two levels of fertilizer.The method of cultivation had no effect on the yield of barley when weeds were controlled by chemicals but, in the absence of such control, the three deeper working methods of cultivation gave higher yields than discing towards the end of the experiment. In the case of wheat, ploughing generally led to the highest yields and rotary cultivating led to higher yields than either cultivating or discing after the ley. Discing led to relatively low yields, particularly with cultural methods of weed control at the lower level of fertility.With the sugar-beet crop, yields of sugar were higher in all rotations after ploughing than after cultivating or discing, irrespective of the method of weed control and although yields after rotary cultivating were similar to those after ploughing in the second rotation they did not consistently exceed those after cultivating or discing in the other two rotations. With discing, in the absence of chemical weed control the yields were markedly reduced in the last rotation period. Ploughing also led to the highest yields of potatoes but there were no consistent differences between the other methods and an apparent trend to lower yields after discing in the absence of chemical methods of weed control had not reached significance by the end of the experiment.It was concluded that ploughing was a more reliable method of seedbed preparation, not only with regard to consistency of performance under different conditions but also with regard to depth of working and extent of weed control.Ploughing appeared to be of particular value with the root crops used but the other methods led to satisfactory yields of the cereals grown after roots.

Description: SUMMARYTwo chickpea pure lines, one being short and wide in stature and the other tall and narrow, were crossed. Parents, F1 and F2 generations were grown in the field to study the inheritance of plant dimensions, as well as their correlation with seed yield. Heritability, in broad sense, for plant height and width was 36 and 20% respectively. Estimated minimum number of genes for plant height was two and for plant width was three pairs of genes. Plant height showed correlation values of 0·43 and -0·67 with yield of seed and 1000 seed weight respectively. There were no significant correlations between plant width and the same two yield components.

Description: SUMMARYHoneybees were able to distinguish between the flowers of two different oultivars of kale grown to produce hybrid seed and most foraged only on one or other of them.

Description: SUMMARYWork that has been reported from some African countries indicates a dependence of grain yield in maize on the duration of leaf area after flowering. This paper studies maize yield in south-east England and confirms work at a similar northern latitude in Canada which has shown that considerable remobilization of photosynthate from the stem to the ear takes place during the main ear fill period.A similar grain yield was obtained from two contrasting hybrids. In a short early hybrid, Kelvedon 75A, there was a low peak leaf area index (5·3) but the net assimilation rate was high due possibly to efficient light interception by leaves that maintained an erect posture. Stem dry matter was also low and hence in this hybrid the high reproductive/vegetative ratio shows that there has been economy in the production of leaves and stem, especially as a 48% stem loss occurred during the period of ear fill.In contrast, in a later hybrid, Anjou 210, the final shoot dry matter was 20% higher as the peak leaf-area index of 7·7 gave slightly higher crop growth rates than K 75A. Although the remobilization of stem dry matter was similar in both hybrids it was notable that a different partition of dry matter in the ears of Anjou 210 gave a higher grain/rachis ratio.

Description: SUMMARYSignificant differences were found in the flavour characteristics of stewed minces from lambs raised on either lucerne or phalaris pastures. The meat from lambs raised on lucerne had a more intense ‘sharp’ and ‘sickly’ aroma and flavour and a significantly lower flavour acceptability. These characteristics were not significantly alter when the lambs were starved for up to 3 days before slaughter. However, the flavour of meat from lambs transferred from lucerne to phalaris 7 or 14 days before slaughter was not significantly different from that of lambs grazed solely on phalaris.

Description: SUMMARYIn oven-dried whole plants from three regrowths of four varieties of Panicum maximum, leaf and stem of normal and stunted oats at three stages of first growth, leaf and stem of rape and the whole plant of millet, cell wall ranged from 14 to 77% of the organic matter. In vitro digestible cell wall ranged from 13 to 46% of the organic matter and was closely related to the cell wall (residual standard deviation, ± 2·5). In 16 legume hays the average in vitro digestible cell wall was 22·1% of the forage organic matter compared with an average value of 20·5% found previously from in vivo digestibility experiments with legumes. An unsatisfactory feature of the in vitro digestibility determination was that in silages and low quality grass hays, the digestible cell wall was low relative to known in vivo values for these forage types. The separate determinations of cell wall and in vitro digestible cell wall would add to the confidence that can be placed on estimates of in vivo digestibility from laboratory measurements. Often, the determination of cell-wall content is sufficient for this purpose.

Description: SUMMARYIn each of the crops studied, weeding increased grain yield, weeding 2 weeks after sowing being better than weeding either four or eight weeks after sowing and weeding two and four weeks after sowing being better than weeding either two and eight weeks or four and eight weeks aftersowing. Weeding thrice (two, four and eight weeks after sowing) was significantly superior to all the other weeding treatments. Weeding increased leaf area index, dry weight of side and mainstem and number of mature pods at harvest in green gram and cowpeas. In sorghum, apart from increasing leaf area index, it also increased the length of ears and grain weight per unit lengthof ear. The weeding treatments affected grain yield in cowpeas and green gram due totheir influence on leaf area development, development of the main and side stems and on the number of mature pods produced at harvest. The effect of the weeding treatments on grain yield of sorghum was due to their influence on leaf area development, length of ear and grain weight perunit length of ear.

Description: SUMMARYThree experiments were made, in which two, four and three sheep were given rations in which increasing amounts of linseed oil fatty acids or Unseed oil were incorporated.Although the changes in the rumen fermentation patterns were similar in all sheep, in some sheep the lipid metabolism in the rumen appeared abnormal, inasmuch as there was considerable accumulation of palmitic and smaller amounts of myristic acid.It was concluded that the increases in the concentration of palmitic acid were due to an increased rate of its synthesis in the rumen, and an attempt was made to calculate these rates approximately.The significance of these results within the context of rumen fermentation, methanogenesis and its inhibition were discussed.

Description: SUMMARYHerbage samples from 16 trials testing the effects of N, P and K fertilizers and slurry on grassland were analysed for % N, P, K, Ca, Mg and Na. The data were examined to see if a fertilizer policy designed for optimum yield should be modified after taking pasture mineral content into account.The correct fertilizer nitrogen policy appears to be to apply nitrogen for the desired yield and to disregard any effects on mineral content. The correct fertilizer policy for phosphorus and potassium is to steer a middle course between depleting soil reserves and accumulating undesirable excesses. The quantities of phosphorus and potassium which should be applied to cut grass to maintain the status quo in the soils are discussed. The amount of phosphorus and potassium added in slurry must be allowed for in this calculation. As the amount of slurry available depends upon the farming system, an effective fertilizer policy for phosphorus and potassium can only be devised by studying the farm as a whole.At the first cut, the slurries provided on average 115 kg NH4-N/ha, 114 kg K/ha and 86 kg P/ha. Slurry potassium was somewhat less than half as effective as fertilizer potassium in increasing % K in the herbage at the first cut. Furthermore, the herbage recovered only 0·8 kg of the 86 kg of slurry phosphorus. In the short term, slurry was only just over 10% as effective as fertilizer phosphorus, presumably because much phosphorus in it is organically bound.

Description: SUMMARYVariation of cotton yields from year to year has been a major problem in the Sudan Gezira for a long time. Previous studies indicated involvement of pest attack, soil nitrogen levels and lengths of growing season in this and suggested that adequate control of these factorswould lead to consistently high yields. Factorial experiments to test this hypothesis, comparing plots sown in early or late August, with or without frequent insecticide spraying and with orwithout nitrogenous fertilizer were therefore carried out at each of five sites in the Sudan Gezira and the first five years’ results are presented.There were large, positive responses to nitrogen, spraying and early sowing at all sites. Nitrogen and spraying interacted positively, i.e. the response to nitrogen was much greater on sprayed plots and the response to spraying much greater on fertilized plots. Where plots were sprayed, early sowing also increased the response to nitrogen.Treatment responses varied from year to year in such a way that the optimum combination resulted not only in much higher average yields but also in greatly improved stability of yield from year to year. The average yields, and the response to nitrogen on sprayed plots, were up to the levels which previous regression studies had estimated would be obtained in the absence of serious pest attack and were similar to peak yields in earlier years. During the course of theseexperiments commercial crop practice has changed towards earlier sowing, heavier nitrogen dressing and more frequent spraying, with apparently beneficial effects on yield and consistency of cropping.

Description: SUMMARYThe influence of three rates of each of N, P and K fertilizers on the availability of native and applied Mn to wheat was studied in a field experiment on an alluvial soil of the Indo-Gangetic plain. Increasing dressings of N as ammonium sulphate resulted in consistently higher yields and Mn uptake by the crop. Concentration of Mn in the grain increased with increasing N dressings when native Mn and Mn fertilizer supplied this nutrient but it was unaffected inplants sprayed with Mn. Adding P as superphosphate tended to lower the concentration of Mn in the grain when relying on native or applied Mn but it significantly enhanced the crop yield and total Mn uptake. Applying K as muriate of potash slightly depressed Mn uptake by plants. Potassium had a more pronounced effect in the absence of P fertilizer. The concentration of Mn in thestraw was not significantly affected by N, P and K fertilization.

Description: SummarySix successive trials with three adult rams (Sudan desert sheep) were conducted with the main object of finding a suitable index for the prediction of the nutritive value of protein in non-legumes for ruminants.The mean change in the concentration of ruminal ammonia, blood urea and ruminal V. F. A. 3 h after feeding legumes was considerably greater than after feeding the nonleguminous hays. Among the legumes berseem hay gave the least change in the concentration of ruminal ammonia, blood urea and V. E. A. The leguminous hays produced more gas under in vitro conditions than the non-legumes. Berseem hay produced the greatest volume of gas. Butterfly pea hay and lubia hay gave more or less similar results. Among the non-legumes the desert grasses gave the lowest values.Of all the feeds studied maize hay gave the highest nitrogen retention, followed by berseem hay. Despite this superiority of maize hay, the overall mean nitrogen retention of legumes was much greater than that of the non-legumes. Among the non-legumes dry desert grasses displayed a negative nitrogen balance.Regression equations based on the present data indicated that nitrogen retention only of leguminous hays could be always predicted from changes in blood urea concentrations. The present results also showed that the nitrogen retention of non-legumes and to a lesser extent that of all feeds taken together (i. e. legumes and non-legumes) can be assessed by using volume of gas produced in vitro (i. e. rate of in vitro fermentation).

Description: SummaryPulverized fuel ash and fiuidized combustor ash were used to modify the availablewater capacity and moisture characteristics of a gravelly sandy loam soil in a study of the effects of fine-particle amendments on crop yield. Intimate incorporation of the ashes into the top-soil at rates of up to 502 t/ha increased the available water retained in the surface 0·3 m of soil by 40–80 %. The increase was mainly water held at potentials of between –0·05 bar and – 1 bar.Two sugar-beet crops followed by broad beans, salad onions and cabbage were grown in the amended soil. With the highest rate of ash addition yield of the onions was increased by over 30% and of the cabbages by 14%. No improvement in sugar-beet or broad-bean yields resulted from the treatment. Poor growth of the second sugar-beet crop was attributed to a reduced aeration effect but it is suggested that the failure of the increased available water to improve yield consistently in this and a previous experiment was in part caused by rapid evaporative losses from the amended soil.

Description: SummaryLower concentrations of the herbicide M15 stimulated the in vitro cellulose digestion and V.F.A. production by rumen micro-organisms. The herbicide Cotoran enhanced cellulose digestion but had no effect on V.F.A. production. The herbicide Dalapon decreased cellulose digestion and had little effect on V.F.A. concentrations. The herbicide 2,4·D had little or no effect on the in vitro cellulose digestion and V.F.A. production. The in vitro microbial activity was inhibited by the pesticide DDT. The effects of M15 2,4·D and DDT on V.F.A. production decreased with time. When the rumen fluid was fractionated, the V.F.A. production by the bacterial fraction was not significantly altered by the addition of 2,4·D and M15, whereas the activity of protozoal fraction was greatly enhanced. The response of V.F.A. production by washed suspensions of rumen ciliate protozoa to the addition of pesticides and herbicides was remarkably similar to that of rumen contents. Feeding M15 (60 ppm) increased the ruminal V.F.A. over those in the control sheep whereas 2,4·D had no or little effect.

Description: SUMMARYThree maize hybrids (Kelvedon 75A, Kelvedon 33, and Anjou 210) were grown under irrigated conditions at a wide range of density from 5·4 to 21·6 seeds/m2 at a rectangularity of 1:1. For yield of digestible dry matter at the time of silage harvest (7 October) a seed rate of 10·8 seeds/m2 (44000/acre) appeared adequate, as doubling the density to 21·6/m2 only resulted in 7% higher yield. K 33, which is a late·maturing hybrid bred for silage in south-east England (50·5–52·5 °N) produced the highest total yield of digestible dry matter due to a high yield of digestible stem. However, the dry matter % of this material would be too low for good ensilage and for a high level of feed intake. In the early grain hybrid K 75 A, 62% of the digestible dry matter was contained in the ear at the silage stage which improved the digestibility and dry matter % of the whole crop with only a 12% lower yield than K 33.The optimum density for grain was 10·8 seeds/m2. This is a higher response to density than is believed to occur in field crops in Britain as in these experiments the seed was planted on the square and irrigation was applied at moisture sensitive stages. The parabolic relationship between grain yield and density was closely related to grain number per unit area. At 10·8 seeds/m2 all three hybrids were of similar yield and grain number per unit area. In Anjou 210 this was achieved with one large ear per plant, whilst for the two Kelvedon hybrids mean ear production was 1·34/plant but with 27% fewer grains per ear.

Description: SUMMARYMagnesium deficiencies have occurred on most crops grown on sandy soil of the Cottenham Series at Woburn (Bolton & Penny, 1968). This paper gives the results of an experiment on this soil comparing the relative effects of dolomite (MgCO3. CaCO3), Epsom salt (MgSO4. 7H2O) with and without limestone (CaCO8), and calcined magnesite (MgO) on the yields and composition of sugar beet, potatoes and spring wheat grown in successive years. Effects on soil composition are also given.

Description: SUMMARYExperiments are described in which the relative importance of head storage capacity and carbohydrate supply was examined in five sorghum varieties of different heights. The varieties were: Namatera (270 cm), Dobbs (180 cm), MUS 78 (100 cm), MUS 23 (85 cm) and MUS 70 (85 cm). Techniques used were (i) cutting off part of the head or part of the leaf at anthesis, (ii) shading during different periods of development, and (iii) thinning the plants at different physiological stages. Varietal differences ranged from a situation where the head was little more than half-filled by the available carbohydrate (MUS 78), through intermediate stages (Dobbs and Namatera), to a situation where the head capacity limited the amount of carbohydrate which could be stored (MUS 23 and MUS 70). Some differences could be attributed to pre-anthesis competition between head and stem, but in the dwarfs a more important factor appeared to be pre-anthesis competition between head and leaf. It is suggested that for maximum efficiency of grain-yield production, maximum carbohydrate should be utilized for pre-anthesis head and leaf growth and that partitioning between these plant parts should be such that the supply of carbohydrate for grain filling is in balance with head storage capacity.

Description: SUMMARYTwenty-three shorn, adult Merino sheep weighing 22·6–63·1 kg were killed and total skin surface area and eight regional skin surface areas measured after skinning. Bodyfat content (1·9–43·6% of body weight) was estimated from the tritiated-water space and body dimensions were recorded before slaughter.Body weight was the best single measure for predicting total area and regional areas, and little advantage was gained by using multiple regressions incorporating body weight, fat content and body dimensions. Proportional surface areas of all regions except the neck were significantly related to body weight; positively for the trunk, and negatively for the ear, lower leg, upper leg and head. Equations relating regional surface area (% total area) to body weight are presented.

Description: SummaryProcedures for measuring K+ and NO-3 activities in the root zones of field crops, using specific-ion electrodes, were standardized. For K, a 1·0 M-NaCl salt bridge and KC1 standards in water, for NO3, a saturated KC1 salt bridge and KN03 standards in water, and for both electrodes, a 1:0·5, soil: water ratio, and 30 sec equilibration time were found satisfactory.Recovery of added K in soil pastes by the K electrode and chemical analysis of the soil water extract compared well, but the recovery was about 8% only. The corresponding recovery of added N was about 87 and 95% respectively.Relative changes in the rates and magnitudes of NO3 and K concentrations were measured with these electrodes, laterally and vertically, in the root zone, during active crop growth, from the N2 ½(PKNaMg), N2 PKNaMg, and N4PKNaMg treatments of the Broadbalk Winter Wheat Experiment.In all fertilizer treatments, at all times, the nutrient concentrations were most at 45 cm from the crop (in the uncropped area) and least within the cropped area. The differences between these extremes represent nutrient depletion by the crop, the ‘45 cm’ measurementsindicating changes in uncropped, but fertilized, areas.Soil nitrate depletion by the crop was much more at 12·5 cm and 20 cm depths than at 5 cm. Maximum NO3 depletion was observed during the later stages of crop growth, at ‘pre-panicle emergence’ and at ‘grain filling’. Depletion decreased and the soil NO3 level recovered partially as the crop reached maturity.Periodic changes in the K concentration at each site and the corresponding K depletions were much less. Periods of IC stress on the soil were few and less clearly demarcated. Soil K concentration started to recover at the ‘grain filling’ stage about a month earlier than with NO3.Changes in NO3 and K concentrations seem to relate more to the amounts given of each nutrient, than to the N:K ratio in each fertilizer treatment. However, changes in NO3 and K concentrations, and also NO3 and K depletion, occurred consecutively. This indicates an alternating periodicity in the demands of the crop for NO3 and K respectively throughout growth.

Description: SummaryResults of matings made in the Belmont breeding programme from 1954 to 1968 have been analysed. The analysis has been made within three groups. (1) The foundation cows in the years 1954–9; (2) the F1 generation which were mated within line in the years 1957–62; (3) the F2 and F3 generations which were mated within Africander cross (AX), Brahman cross (BX) and Shorthorn-Hereford (SH) lines in the years 1960–8. Fertility was based on the number of calves born, whether alive or dead, to the number of cows mated.In the foundation cows, Hereford cows had a fertility 9% higher than the Shorthorns. The difference between the bull breeds was not significant although the mean for the Brahman bulls was 16% below the mean of the other three breeds. There was a large variation in the fertility of the Brahman bulls. The fertility of the Shorthorn cows was depressed (by 8%) in the lactating cows as compared with dry cows, while there was an opposite effect in the Herefords. These latter effects showed year to year variation.In the F1 generation the differences between the breeds were not significant although both the AX (76·4%) and the BX (81·2%) were more fertile than the SH (70·1%). Estimates of heterosis in the F1 generation were 42% for the AX, 43% for the BX and 12% for the SH. Lactating cows were 7% more fertile than non-lactating cows. There were significant differences between the BX bulls used but not between bulls of the other two breeds. The effect of sires within breed on fertility of daughters was significant only within the SH, and the heritabilities of fortuity were estimated from the variance components for sires within breed to be 9%, 14% and 22% for AX, BX and SH respectively.In the F2 and F3 data the breeds were significantly different in fertility with averages of 77%, 61% and 67% for AX, BX and SH respectively. Thus by comparison with the fertilities of the F1 cows no loss of heterosis for fertility occurred in the AX, a very marked loss in the BX and only a slight loss in the SH. A significant interaction between age of cow and lactational status showed that in the mature cows, wet cows had a higher fertility than dry, while the converse applied in the 3-year-old cows. The interaction of lactational status with breed consisted of the wet zebu cross cattle having a relatively low fertility while the wet British cattle had a relatively high fertility. There were significant differences between bulls within each of the three breeds. The effect of sires was significant in the BX and SH. Heritabilities estimated from between sires within breeds variance components were – 12%, 22% and 25% for the AX, BX and SH respectively.

Description: SummaryAn experiment at Sutton Bonington in 1971 tested the effects of sowing and harvesting dates on yield of sugar beet. Seed sown on 28 March germinated slowly in the cold soil and crop establishment was poor. From early April until the beginning of May the loss in yield of sugar consequent upon delaying sowing by 1 week was 0·4 t/ha. For later sowings the yield loss was greater. During the harvest period the rate of increase in sugar yield was the same for all sowings. Yields of crops sown and harvested on different dates were closely correlated withthe amount of solar radiation intercepted by the leaf canopy.

Description: SummaryEstimates were made at monthly intervals between January and December 1965 of the intake and nutritive value of the diet of unmated Merino ewes grazed continuously at stocking rates ranging from 2·5 to 37·1 sheep/ha. Oesophageally fistulated sheep were used to estimate intake and nutritive value.Drought conditions existed during the experiment. Digestibility declined linearly with increasing stocking rate. The intercepts of the relationship between digestibility and stocking rate differed between months, being at a maximum in spring. Nitrogen content was also greatest in spring but did not change consistently with increasing stocking rate. Organic-matter intake declined linearly with stocking rate and increased asymptotically with total herbage available, the asymptotic relationship being the more precise. Neither relationship differed significantly between months. Organicmatter intake/ha increased continuously with increasing stocking rate and the maximum intake was predicted to occur at a stocking rate greater than that at which the sheep survived.

Description: SummaryThe carcass characteristics of a total of 43 infertile bulls were oompared with those of 42 steers from five independent trials. In most cases there was no significant difference between the bulls and the steers for dressing percentage, or fleshing index. Bulls were generally found to have greater hide percentages than steers, the difference being very highly significant (P 〈 0·001) in one of the trials and significant (P 〈 0·05) in another. Eye musole area expressed relative to caroass weight was greater in the bulls, the difference being significant (P 〈 0·05) in three of the trials. The depth of fat over the eye musole and the hind to fore-quarter weight ratio were greater in the steer carcasses. Head weights were found to be significantly greater (P 〈 0·05) and caul and kidney fat weights less (P 〈 0·05) in bulls than in steers in the one trial where these parameters could be measured.Carcass composition was estimated by the three-rib sample joint teohnique in four of the trials, and in these the bulls had a greater percentage of bone and muscle, but a lower peroentage of fat than the steers, the differences being significant in most oases. In the fifth trial composition was estimated by half carcass dissection. This, too, showed bulls to have a greater percentage of bone and muscle and a lower percentage of fat, the differences being highly significant (P 〈 0·01) and very highly significant (P 〈 0·001) respectively. On a fat-corrected basis the estimated retail value of the carcasses favoured the bulls by about $20.00 each.The studies, conducted over a range of nutritional conditions, showed that non-castration favoured muscle growth while suppressing fat deposition, and that this advantage was more pronounced when growth rates were high.

Description: SummarySymptoms of magnesium deficiency and take-all disease occurred during 1967 in wheat grown for the second year in succession on the ‘Classical’ cereal site at Woburn. Magnesium fertilizers, which cured the deficiency symptoms and increased wheat yields in 1968 and 1969, had no effect on take-all. Leaves from crops severely attacked by take-all contained less nitrogen and potassium than leaves from unattacked plants but not less magnesium. In 1969 magnesium fertilizer did not increase yields or affect takeall of spring barley on the site but, in contrast to 1968, increased potato yields. Magnesium fertilizer improved the establishment of clover, especially on soil containing least magnesium.Soil analyses show a tenfold decline in exchangeable Mg since 1888. Losses were most from soil given ammonium sulphate and more from the site where wheat was long grown than where barley was. Differences in soil magnesium did not explain large differences in yields of potatoes or leys between blocks of the experiments.

Description: SummaryMeat quality comparisons were made between a total of 43 infertile bulls and 42 steers in five separate trials. Tenderness, juiciness and flavour were tested by taste panel for each of the five trials, making 15 subjective tests, while objective tests were made of tenderness (Warner-Bratzler shear) and juiciness (industrial press) in the five trials, making a further ten tests.From this total of 25 different groups of assessments no significant difference between bull and steer meat was detected in 21; of the four groups of assessments where significant differences were detected, two favoured the bulls and two favoured the steers; the quality of all the samples was acceptable.It is concluded from the overall results that in terms of practical meat quality there was no difference between the bulls and steers used in these five trials.

Description: SummaryIn a series of field experiments from 1966 to 1969, on light sandy loam soils in the West Midlands, comparisons were made between two levels of application of herbicides based on urea, triazine and bipyridil compounds for weed control in early potatoes.Under conditions of adequate nutrient and water supply, the high application rate controlled about 94%, and the low application rate about 88% of the annual weeds. At equivalent application rates, urea compounds and herbicide mixtures containing ureas, gave superior weed control to triazine compounds and herbicide mixtures containing triazines, but the ureas were apparently more phytotoxic to the potatoes.In 1970, comparisons were made between three levels of application of ametryne and monolinuron, high, medium and low and an unsprayed control treatment.The highest yields of potatoes were associated with the low application rates of herbicides from 1966 to 1970.It was concluded that, on these light sandy loam soils, when irrigation is available, relatively low application rates of either monolinuron or ametryne, or mixtures of ureas or of triazines, or mixtures of bipyridils and ureas or triazines could give adequate control of annual weeds in early potatoes at low cost.

Description: SummaryAlthough it is not always valid to regard ‘within herd variation’ as a true measure of experimental error there are occasions when this may be the only feasible measurement. The effect is considered of regarding the animal as the experimental unit on the estimation of the ratio of production of two treatments and an approximate variance for the ratio is obtained. The conditions under which the approximation is valid are considered.

Description: SummaryPollination treatments were carried out on highly inbred lines of winter beans over a period of four years.Tripping produced an inferior seed-set compared with all treatments involving emasculation and hand pollination with either cross or self-pollen. It is suggested that with highly inbred lines the stigmatic surface requires some form of scarification to improve the seed-set. Most lines showed no preference for cross or self-pollen, and there was no evidence of self-incompatibility. Bud and mature flower pollination gave an improved seed-set over tripping in all lines.One inbred line gave a high seed-set in all pollination treatments. Results from another line were consistent with a short period of ovule receptiveness.Using data obtained from three experiments, two self-pollination treatments were used to screen breeding lines for their suitability as components of synthetic varieties. Significant differences in seed-set were found between the lines.

Description: SummaryThe effect of soil water potential of the root media on the vegetative growth, seed and oil yield of sunflower (var. Record) grown in containers under field conditions was investigated.The weight of shoots and the total leaf area of plants before flowering significantly decreased with decrease in the water potential of the root media. There was a sharp reduction of shoot weight as the potential decreased from —0–32 to — 1–25 bars and then a further slow decline as soil water potential dropped to — 8'6 bars. There were no significant differences in the 100-seed weights and percentage. of oil among the treatments, but the total number of seeds was significantly different.The data did not indicate the existence of a threshold water potential above which yield was independent of soil water potential, but rather that yield was a continuously decreasing function of soil water potential.

Description: SummaryEighteen foetal sheep were used to study the relationship between suboptimal growth and linear size of skeletal units, dry weights of representative muscles and muscle histology. Foetuses with suboptimal growth caused by inadequate maternal nutrition and competition with other foetuses showed a decrease in skeletomuscular growth although allometric growth was not affected. A slight correlation (r =0·14, P 〈 0·005) existed between dry weight of the longissimus dorsi and mean minimum myofibre diameter. On morphological evidence, myofibre hyperplasia was thought to be complete by approximately 80 days gestation in all foetuses. Increases in the number of myofibres crossing mid-length transverse sections of the sartorius occurred after this time but were thought to be due to intrafascicularly terminating myofibres growing in length. Suboptimal muscle growth of foetuses in the latter third of gestation was thought to be associated with an inhibition of growth in length of intrafascicularly terminating myofibres.

Description: SummaryTwo hundred and forty mature Merino ewes were used in a factorial experiment to investigate the effects of single injections of either 0, 40, 80 or 160 mg progesterone on the length of the subsequent oestrous cycle. Equal numbers of ewes (15 per group) received subcutaneous and intramuscular injections, and equal numbers were treated either on the day of oestrus or the following day.Oestrous cycle length was significantly reduced in all treated groups, with a minimum cycle length of 7–10 days following treatment with 80 or 160 mg progesterone. Neither route of administration nor day of treatment significantly affected the response. The conception rate achieved by treated ewes at the first post-treatment oestrus did not differ significantly from that in comparable controls.The results suggest that a single massive dose of progesterone on the day of oestrus is an effective means of shortening the oestrous cycle of the ewe without loss of fertility.

Description: SummaryThree different methods have been used to estimate the contribution of bacterial nitrogen to the total nitrogen in rumen digesta from calves receiving ground diets containing different levels of digestible energy and in which part of the nitrogen was supplied as urea. The method based on the ratio of 2, 6-diaminopimelic acid (DAP)-N to total N for rumen contents and rumen bacteria was not successful because the bacterial fraction isolated from pooled rumen contents contained a similar concentration of DAP to whole rumen digesta. The main source of error in the method based on the nucleic acid N/total non-NH3-N ratio for whole rumen contents and bacteria was probably the variability in the ratio for bacteria growing under different conditions. The method utilizing differences in the amino acid composition of the diets, a bacterial fraction and rumen content estimates bacterial protein rather than bacterial nitrogen. The chief limitation is the different rate of degradation of different dietary proteins. Bearing in mind these limitations calculations by the nucleic acid method gave mean values of 61–94 % bacterial nitrogen in the total nitrogen of rumen contents 3 h after feeding four different diets. Values recorded by the amino acid composition method varied between 66 % and 82 % bacterial protein N in the total protein N of rumen contents. The proportional contribution of bacteria increased as the digestible energy content of the diet was decreased in both cases. However, since the ruminal total protein N concentration fell as the digestible energy content of the diet was reduced, the actual concentration of bacterial protein N decreased with decrease in dietary digestible energy.

Description: SummaryA mixed sward of grasses and clovers, previously established with adequate Ca, N, P and K on deep acid peat, was used for a factorial experiment to determine the amounts of nutrients required to produce herbage for conservation. The treatments consisted of all combinations of 0, 117and 234 kg N, 0, 29 and 58 kg P and 0, 156 and 312 kg K/ha, and their effects on the botanical composition of the sward, the yield and mineral composition of the herbage, and the nutrient status of the peat were measured over a period of five years. Three cuts were taken annually, one third of the N dressings being applied for each cut.Tall fescue became the dominant grass species while cocksfoot persisted much better than either ryegrass or timothy. The proportion of clover in the sward was reduced to practically zero by applying N, but without N it was maintained at about 20% by applying K.Yields of dry matter were greatly increased both by N and by K and there was a marked positive interaction between these two nutrients. Due to the marked suppression of clover by applied N there was no response to the first increment of N in 1959, but with this exception, 1 kg N/ha with adequate P and K produced between 15 and 30 kg dry matter/ha. The effect of K increased from 1958 to 1962, the first increment consistently producing most of the response. Applying P had little effect on yield until the fifth year when a significant response was obtained.The mineral composition of the herbage varied during the season; the percentages of N, Ca, Na and Mg were generally higher in autumn than in early summer whereas the percentage of K showed the opposite effect.The N, P and K treatments had large effects on the percentages of N, P, K, Na, Ca and Mg in the herbage and on the amounts removed in the crop. Without applied N, but with adequate P and K, percentage of N varied according to the amount of clover in the sward. With applied N there was less variation and the average percentage of N was about 1·7 with 39 kg N and 2·0 with 78 kg N/ha/cut. Percentage of P ranged from 0·14 to 0·54 and percentage of K from 0·5 to 3·5. Apparent recoveries up to 74, 65 and 96 % were obtained from the N, P and K treatments, respectively.For continuous production by cutting and removing the herbage, a mixed sward containing clovers appears to require, without applied N, about 120 kg K/ha/year. With applied N, an additional 0·3 to 0·5 kg K/kg N appears to be needed. The amount of P required will depend mainly on the concentration desired in the herbage and on the rate of N used. To produce herbage with 0·3 % P in the dry matter about 15 kg P/ha/year, plus approximately 0·1 kg P/kg N applied seems to be needed; for 0·4 %P the corresponding quantities are about 40 kg P/ha plus 0·3 kg P/kg N applied.

Description: SummaryThe results of a field experiment on winter wheat are presented in which the effects of the soil physical properties produced by different cultivation systems were studied in relation to root development.The extension rate of the seminal root axes was slower in undisturbed or shallow (5 cm) cultivated soil than in ploughed or deep (20 cm) cultivated soil leading to earlier lateral branching and the production of an effectively shallower seminal root system which persisted throughout the season. During the first four weeks after drilling the soil in the ploughed and the deeper cultivated plots was of lower bulk density and there were more pores of a diameter suitable for unimpeded root extension. It is suggested that seminal root development in uncultivated soils, which are less readily deformed than cultivated ones, is related to the probability of the extending seminal axes contacting pores of suitable dimensions.The implications of shallower rooting are discussed and related to field experience with cereal crops drilled directly into uncultivated soils where success has consistently been achieved on free-draining, open-textured soils.

Description: SummaryThe project involved two breeds of Indian goats – Barbari and Jamunapari, three levels of energy and three levels of protein, making a total of 18 treatments. There being no specific recommendations for goats, the high, medium and low levels of energy (T.D.N.) and protein (D.C.P.) represented 125, 100 and 75% of Morrison's standard for sheep, respectively. A total of 97 Barbari and 87 Jamunapari does were allocated to the nine ration treatments and were bred within the breed naturally. The rations comprised a concentrate mixture (linseed cake and/or barley grain), dry roughage (gram bhusa), greens, mineral and trace-element mixtures and common salt. The effect of nutrition on reproductive performance, as revealed by the five and four kiddings completed in the Barbari and Jamunapari was as follows:While the first kiddings did not indicate a sizeable effect, the subsequent ones showed a significant effect of nutrition. Almost all the does in the low-energy groups, irrespective of the protein levels, did not kid for the last kidding under reference.The maximum percentage of twins was noted in high-energy-cum-high-protein (47·5%)and high-energy-cum-medium-protein (45·3%) groups of Barbari and Jamunapari respectively. The average twin-birth percentages, irrespective of nutrition, were 14·8, 37·3, 38·0 and 40·2 in Barbari and 9·0, 20·5 and 23·0 in Jamunapari respectively. Triplets, although rare, occurred within the Barbari but only one case occurred within the Jamunapari.On average Barbari and Jamunapari had 2·0 and 1·5 kids per doe per year in the high-energy-cum-medium-protein group compared with 1·0 and 0·4 in the low-energy ones, respectively. Furthermore, high- and medium-energy groups had shorter intervals between kiddings compared with the low-energy ones.

Description: SummaryThirteen field experiments were made during 6 years on seed-potato growing farms in south-east Scotland, comparing three rates, 70, 140 and 280 kg K/ha as potassium chloride and four rates of 0–54 kg Mg/ha as kieserite in 3 × 4 factorial experiments.More than 70 kg/ha of potassium increased total yield only at one site, which had a recent history of low K application and very low available K. Yields were decreased by more than 70 kg/ha of potassium at three sites in a season with abnormally dry conditions just after planting. Applied magnesium had little effect on total yield.Extra potassium increased ware yield but decreased seed yield, both consistently, probably because the fertilizer damaged some stolons at or before tuber initiation and fewer tubers developed. The ware/seed ratio was generally increased by extra K, but after the dry spring this ratio was unaltered or reduced. Applied magnesium had little effect on the ratio.Our results suggest that the present rates of K fertilizer, used for commercial seed-potato crops (114–138 kg K/ha) in south-east Scotland are excessive, and a much lower rate of approximately 70 kg K/ha would be adequate except on very low K sites.

Description: SummaryThe effect of altering the level of protein intake on urea excretion in ewes was assessed in two separate experiments.In Expt 1, 14 pregnant (during the last 20 days of gestation) and 10 non-pregnant ewes were each offered a different level of digested N intake in the range 5–25 g/day. At all levels of protein intake urea N excretion was lower in pregnant than in nonpregnant ewes.In Expt 2, 21 pregnant ewe lambs were each offered one of three diets supplying mean intakes of 83 (T1), 113 (T2) or 147 (T3) g crude protein/day. During the last 100 days of gestation the mean levels of urea N excretion were 6·9, 11·0 and 15·2 g/day for T1, T 2 and T 3, respectively. The corresponding values for urinary N excretion were 9·3, 13·8 and 18·2 g/day. At all levels of protein intake urea N excretion was lower just prior to parturition than 95 days prepartum; the difference was correlated with lamb birth weight and maternal body-weight change.A notable feature of both experiments was the low level of urea N excretion by the pregnant ewes in late gestation, at low protein intakes. It would appear that when energy intake is adequate the decrease in urea N excretion associated with pregnancy is a direct result of an increased N requirement for maternal and/or foetal growth.

Description: SummaryA dynamic model is presented in which the problem of predicting P response is broken down into various components, such as:(a) Weight and P content of emerging seedling.(b) Normal growth curve of the fully nourished plant.(c) A ‘deficiency-tolerance’ factor relating depression of relative growth rate to plant P concentration.(d) An ‘affinity’ term relating sink concentration to P status of plant.(e) A perirhizal resistance term for diffusive transport to roots.(f) Capacity and intensity of P supply from the soil. Mass flow supply via the transpiration stream is also included.By changing parameter values one may attempt to simulate the effect of any of these factors on the shape of the P response curve and any other part of the system throughout crop life. At present the model over-estimates growth at low levels of P supply, but predicted plant P concentrations agree reasonably well with observed data.

Description: SummaryDetached, fully turgid leaves of S. 24 perennial ryegrass were sprayed with 1, 3 and 5 mg of a solution of 85% formic acid per leaf and dried in controlled conditions (temperature 28 ± 1 °C, relative humidity 22 and 64%, air speed 40 cm/s). The lowest rate of application increased the rate of leaf drying approximately four times when the relative humidity was 64%. Increasing the rate of formic acid or reducing the relative humidity to 22% did not enhance the drying further. The mode of action of formic acid is discussed. It is suggested that formic acid might be utilized to obtain quicker drying of grass for hay, and further investigations are called for.

Description: SummaryPot-culture experiments were made with the rice variety IR-8 on a sandy clay loam soil to study the relative efficiency of urea, urea treated with nitrification inhibitors N-Serve and AM, AM-fertilizer, and slow-release nitrogen fertilizers IBDTJ, oxamide and N-enriched coal. N-enriched coal supplied very little nitrogen to rice and gave no more yield than the control. All other materials were superior to urea. Largest yield of rough rice and nitrogen uptake by rice was obtained with IBDU and AM-fertilizer. Compared with untreated urea IBDU, oxamide, AM-fertilizer and urea treated with N-Serve or AM left larger amounts of mineral-nitrogen in the soil after the harvest. In the case of nitrification inhibitors residual ammoniacal-nitrogen was more at the higher rates of inhibitors.

Description: SummaryResponse to selection primarily for lint yield among spaced plant populations of four American and one African variety of Gossypium hirsutum L., established in 1965—6 at Kimberley Research Station, was studied in three experiments conducted between 1966 and 1970.In the first experiment, in which single-hill micro-plots of 3–5 plants per hill were used, the mean lint yield of progenies was larger than predicted from single plant heritabilities. In the second experiment, in which single-row plots were used, response to selection for lint yield was generally less than expected. In the third experiment, in which three-row plots were used, response to selection for lint yield was again less than expected and less than manifested in the second experiment. However, in all experiments responses to selection for lint percentage, lint quality properties, and height were close to expectations while some individual progenies substantially out-yielded their unselected parents.The progressive decline in response to selection for lint yield from the first to thethird experiment, and the discrepancies between the actual responses and the expected responses for lint yield in all experiments, were interpreted mainly on a basis of intergenotypic competitive effects differing in sympathy with plot size and plant disposition.It was concluded that the objective methods of selection practised were successful when judged on plant breeding criteria. It was also concluded that intra-varietal selection is an important technique by which genetic improvement can be achieved at regional breeding centres with limited resources.

Description: SummaryThe optimal intensity of P supply for lettuce was investigated in a pot experiment with five soils, six levels of P application (0, 15, 30, 60, 120, 240 ppm) and three times of harvest (2, 3 and 4 weeks after emergence). The P adsorption isotherm for each soil was measured in 0.01 M CaCl2.All soils responded strongly to P application, the amounts required for maximum growth varying from 120 ppm on a sandy soil to 300 ppm on a moss peat. The differences in requirement were related to the P adsorption by the soil, and on all soils a solution P concentration of about 1 ppm resulted in maximum growth.The Optimal leaf P concentration in young lettuce was about 0·6%.

Description: SummaryExperiments were carried out to assess the effects of silage diets given with and without supplementary energy as barley and/or nitrogen as groundnut meal or urea on rumen fermentation in growing heifers.Silage based diets resulted in a stable pH and a high molar percentage of acetate in rumen liquor. Total V.F.A. concentrations were significantly increased by supplementary energy plus protein but were not consistently increased by energy only, and were linearly related to M.E. intake but not to D.M. digestibility. Effects of energy and nitrogen supplementation on the molar percentage of rumen V.F.A. were small and not always significant.Rumen NH3-N levels were normal on the basal silage diets and were linearly related to N intake. Levels were significantly reduced by energy supplementation but significantly increased by protein supplementation. Results are discussed in relation to energy and nitrogen utilization on silage based diets.

Description: SummaryForty merino sheep of mixed ages including lambs, ewes, wethers and rams were slaughtered and dissected. The chemical fat content often muscle groups in each sheep was measured directly and the mean value for the musculature of the whole carcass calculated.A characteristic pattern of chemical fat deposition was shown with the intercostal muscle group and the abdominal group being consistently highest in fat content, the shin and hind-limb muscles lowest and other intermediate. The pattern of growth of intramviscular fat was consistent with differences in activity of the muscle groups in the maintenance of posture. It was postulated that variations in fat content in muscle groups are affected by differences in blood flow.A highly significant relationship was established between dry matter and chemical fat content for each of the muscle groups. The regression was characteristic for each muscle group, and differed for most groups.Regressions between individual muscle group fat and that of total musculature fat revealed that no group was consistently the best predictor of the total carcass musculature fat though there was considerable difference between the groups. It was concluded there is no group which could be used for prediction purposes commercially.In a group of 14 other ewes subjected to weight loss up to 30%, and half of which were implanted with resorcylic acid lactone, no discernible effects on muscle group fat content were revealed.

Description: SummaryAn experiment comparing six-course rotations which included 1-, 2- and 3-year leys of pure grass, pure legume and grass/legume mixture is described, and the results from the fifth and sixth phases of the first cycle and first and second phases of the second cycle are discussed.Compared with all-arable cropping, the inclusion of leys increased the yield of barley grown as the second and third crops after the leys were ploughed up, although the difference was less when 58 kg N/ha had been applied. Neither length nor type of ley affected yield in the second crop after ploughing the leys, but in the third crop 2- and 3-year leys led to greater yield than 1-year leys.Only rotations containing 1-year leys were compared with all-arable cropping in the fourth and fifth crops after ley, but some effects of these were still apparent in that both Italian ryegrass and broad red clover leys led to an increased sugar percentage of sugar beet grown as the fourth crop when no nitrogen was applied, and broad red clover leys led to a greater response to nitrogen in barley grown as the fifth crop after ley.

Description: SummaryFour of five ‘hairy’ Wiltshire lambs had fibre type arrays (as defined by Dry, 1965) of Plateau (P0 and P1) type, whereas in five ‘woolly’ lambs there was only one Plateau (P3) array, the arrays of the remaining lambs being Ravine or Saddle. In terms of Dry's theory that the severity of pre-natal check determines persistence of wool growth in adults, it appears that the amount of checking in these Saddle and Ravine arrays was insufficient to prevent the casting of the adult coat.

Description: SummarySeveral alternative statistical approaches to the analysis of genotype-environment interactions are summarized, and their inter-relationships are presented mathematically and graphically. An experiment was designed to test the ability of these analyses to satisfactorily describe genotype-environment interactions and to locate genotypes causing or contributing significantly to such interactions in a situation where environments differed in only one factor, i.e. soil nitrogen status.Twenty-five lines of wheat were grown at each of 5 levels of applied nitrogen (0–270 kg N/ha) in a sandy, nitrogen-deficient soil, and their grain yields and yield components (ears per unit area, grains per ear, weight per grain) were determined. Designating the nitrogen levels as ‘environments’, linear yield responses, and deviations from linear responses, of individual wheat entries to environment mean yield were calculated according to the various statistical procedures previously outlined. The results suggested that the linear response to environment mean yield was similar for all wheat entries. However, further inspection of the data revealed that the responses of eight entries to environment mean yield departed significantly from linearity. Although several analyses satisfactorily identified these aberrant entries, classifying them as ‘unstable’, it was concluded that the degree of departure from linearity of response was not an adequate measure of instability. Furthermore, as previously suggested by Knight (1970), it was confirmed that the relative ranking of an entry for yield stability according to such a concept varied according to the average response of the group of entries with which it was being compared.The general effects of applied nitrogen on yield components were to increase the number of ears and the number of grains per ear, and to decrease grain weight. However, only the first of these effects occurred consistently for all entries. The number and weight of individual grains per ear varied with the nitrogen treatment, often unpredictably, in a complex pattern which differed significantly between entries.

Description: SummaryGrowth rates, chemical composition of the body and wool production were measured with wethers and ewes from two genotypes of sheep grazing at two planes of nutrition. The nutritional treatments were applied after weaning at 12 kg live weight. Animals were slaughtered at 6 kg intervals between 12 and 54 kg live weight.Dorset Horn × (Border Leicester × Merino) lambs grew 57% faster than South Australian Merino lambs before weaning, produced 22% more wool and contained more fat at weaning.Post-weaning growth rates on the high and low planes of nutrition were 168 and 78g/day for Merinos and 183 and 116 g/day for Cross-breds. Despite these differences, there was virtually no effect on body composition. Sheep which were starved and re-grown also had a similar body composition to sheep grown continuously.There was, however, a nutritional effect on wool production. On the high plane of nutrition the rate of wool production was 22% higher than on the low plane of nutrition.After weaning there were only small differences in the growth rate of the two genotypes but the Merinos grew 30% more wool than Cross-breds on the high plane of nutrition and 39% more wool on the low plane of nutrition. Genotype differences in the fat and protein content of the empty body were small, but Merinos contained more ash, Ca, P and Mg.After weaning the normal pattern of allometric growth was reversed; at 18 kg live weight the sheep contained a lower proportion of fat and higher proportion of water than at 12 kg live weight. Above 18 kg live weight normal allometric growth was resumed. The fat-free empty body became progressively less hydrated but the ratio of protein: ash remained constant at 79:21 for Merinos and 81:19 for Cross-breds.There was a trend towards ewes being fatter than wethers, but this was only significant with Merinos. Other sex differences in body composition, body growth and wool growth were not significant.

Description: SummaryForty-four full-sib families from a diallel cross between 10 Lolium ((multiflorum × perenne) × perenne) clones were planted in the autumn at 0·6 × 0·6 m and 0·l × 0·l m spacings. Fresh weight of individual plants was measured on three occasions during the following spring and summer. The analysis of the diallel cross was extended to account for combining ability × spacing interactions, and to estimate between-spacing combining ability correlations and their sampling errors.Family × spacing interactions became increasingly significant at successive harvests and always contributed substantially to the total phenotypic variance. Much of the family × spacing variance was due to the general combining ability (GCA) × spacing component. Despite these large and significant interactions, the correlation between GCA values at the two spacings was high and positive at each harvest, so that selection for yield at wide spacing should lead to a correlated increase in yield at close spacing. Although the experiment was of relatively short duration, the results suggest that recent criticism of the conventional technique of selection among widely spaced plants in pasture plant breeding programmes may not have been entirely justified.

Description: SummaryPopulations of spaced plants of each of the four American upland cotton varieties Deltapine Smooth Leaf, Rex Smooth Leaf, Pope, and Rex and one African upland variety, Bar 7/8, were grown in the 1965–6 wet season at Kimberley Research Station, in the Ord River valley, Western Australia. The number of bolls, boll weight, lint percentage, seed cotton yield, lint yield, micronaire value, mature height, and morphological type were recorded for each plant.For all varieties the range of each attribute was wide; for example, for a typicalvariety, boll weight ranged from 3·0 to 7·8 g, lint percentage from 30·5 to 43·5%, micronaire value from 3·3 to 5·9 units, and mature height from 78 to 195 cm.The most variable varieties judged on coefficients of variation were those maintained at the station for the longest period without selection while the most recent accession was the least variable.Frequency distributions for all attributes in each population departed significantly from normality: the majority showed both significant skewness and kurtosis. Positive skewness shown for the yield parameters seed-cotton yield, lint yield, boll number and boll weight in all varieties suggested there was scope for improvement by selection. Negative skewness for lint percentage was found in three varieties, suggesting previous intense selection for this trait. The coefficient of variation of lint percentage with one variety (Deltapine Smooth Leaf) was considerably less than that recorded 30 years earlier for its predecessor D x PL 11 A.Covariance adjustments to seed cotton yield of individual plants, based on various hypotheses of the relationship between a plant's yield and that of its neighbours failed to give reductions of consequence in the variability of yield. It was concluded that inter-plant influences were far more complex than the models assumed.

Description: SummaryThe distribution of body water in the different body compartments of four highpotassium (HK) and four low-potassium (LK) type sheep of the Marwari breed of the Rajasthan desert was determined after imposing the following watering treatments, viz. watering ad lib., ¼, ½ and ¾ restrictions (each of five days ‘duration with a sevenday normal drinking regime between each treatment) and water deprivation (of three days’ duration). There was no difference in the voluntary water intake of the HK and LK animals. The HK animals normally have a higher blood and plasma volume status than the LK. In both types of animals, the total body water, total blood and plasma volumes and the extracellular, intracellular and interstitial fluid volumes started decreasing as water intake was reduced below 25% of the daily requirement. In both the phonotypes 75% reduction was similar in its effect to complete deprivation. The physiological status of the HK Marwari animals appears to be somewhat superior to that of the LK although both types seem to be equally adapted to the conditions of the habitat.

Description: SummaryPatterns of stem development in late spring/summer regrowths after initial cuts at three growth stages are described. The stages at which the initial cuts were taken were: (a) before stem apices were raised to defoliation level (5 cm), (b) two weeks later when the apices of about 90% of the stem tillers were raised above this height, and (c) four weeks after (a), when the apices of all stem tillers were raised well above cutting height.Following an initial cut at stage (a) stem development was quickly resumed, the most advanced tillers being devoid of leaf blades. After initial cuts at the later stages there was virtually no stem development until after the fourth week of regrowth.The greater proportion of stem tillers in the earlier regrowth was not reflected in reduced digestibility during the first six weeks from cutting.Reproductive (apical) development was generally weak in tillers in which stems developed in midsummer (after cutting at stages b and c); at least two-thirds of these tillers were indeterminate.The significance of the distinct batch of stem tillers developing in spring is discussed, and the data are also considered in relation to (i) avoiding stemmy regrowths in spring, (ii) stem development and herbage quality, and (iii) summer stem extension and the perennation of the sward.

Description: The deposition on soil of sulphur from the atmosphere through gaseous absorption, or particulate precipitation and deposition on vegetation and to other surfaces, is calculated to account for most of the atmospheric-S deposited in Britain; S collected in rainwater appears to amount to only one-sixth of the total deposition (Chamberlain, 1960). A knowledge of the amounts of S deposited is important agriculturally, particularly in areas far from industry, both where fertilizers are not used, and also when deciding how much fertilizer-S should be used relative to other nutrients. The technical problems of separating the amounts of sulphur deposited by gaseous absorption, particulate precipitation, and in rain are easier in a tropical climate which has well-defined wet and dry seasons and where atmospheric SO2 concentrations are smaller and vary less than in industrial areas.

Description: SummaryAmmonium nitrate was applied to a kikuyu (Pennisetum clandestinum) dominant pasture at annual rates of 0, 134, 336 and 672 kg N/ha. Each nitrogen (N) rate treatment was continuously grazed at three stocking rates (SR) designed to apply similar grazing pressures at each N level and covering a range from 2·2 to 16·6 Angus weaner cattle/ha.The N status of these pastures was periodically assessed 8–10 weeks after seasonal N applications by temporarily excluding stock and measuring D.M. and N response to additional ammonium nitrate application. Pasture growth response to additional N was constant and independent of SR and of annual N rate over the range 0 to 336 kg N/ha, despite wide variation in pasture availability. N concentration of plant shoots was increased by high SR and rate of N uptake was not significantly affected by SR. Pasture growth rate was positively related to annual N rate.Herbage yield of kikuyu leaf, stem and litter on offer, was negatively related to SR but weight of underground organs was unaffected. Increasing SR increased the proportion of leaf and the rate of tillering. Pasture availability was positively and linearly related to N rate from 0 to 336 kg N/ha and maximal at 336 kg N/ha; the size of the litter fractions and underground organs was generally independent of N rate. N% in leaf and stem was reduced at low SR; N% of leaf, stem, litter, rhizome and root was positively related to N rate which was more influential than SR. The effect of SR on the size and relative distribution of the N in plant tops and litter fraction is discussed.Kikuyu dominance was positively related to N rate and independent of SR. White clover invaded at No and N131 levels especially at a high SR.

Description: SUMMARYA method of including urea into whole grains is described. The whole grains were found to absorb completely a saturated solution of urea.The method gave the different cereals examined (barley, oats, wheat and maize) a homogeneouis distribution of urea and increased the voluntary intake of whole grains by lambs. The evolution of NH3 in the rumen liquor was slightly slower when urea was absorbed into the grains than when it was included as urea crystals. The N content in the urea-treated grain was not changed after 6 months of storage.

Description: SUMMARYFour young females of four ruminant species, namely cow, buffalo, sheep and goat were used to study the utilization of sun-cured berseem hay (20·6% CP) fed in long form during a 28-day experimental period. Voluntary intake of hay was estimated during the last 10 days and digestibility of feed nutrients and nitrogen balance during the last 6 days.The digestibility coefficients of dry matter (D.M.), organic matter (OM), crude protein (CP), crude fibre (CF), ether extract (EE) and nitrogen-free extract were higher for sheep and goat than for cow and buffalo but such differences were significant for D.M., OM and CP only. The daily D.M. intake was 3·56, 3·17, 0·92 and 0·63 kg/animal and 82·5, 81·2, 70·4 and 65·1 g/kg W0.75 in buffalo, cow, sheep and goat, respectively, but intake of total digestible nutrients (TDN) relative to metabolic body size was similar for all species.Buffalo was superior to the other three species and cow to sheep and goat in ability to retain nitrogen. Berseem hay fed ad libitum supported a daily gain of 742, 500, 71 and 31 g in young female buffaloes, cows, sheep and goats, respectively. Digestible CP values of 13·33, 13·47, 15·38 and 15·01% and TDN values of 59·8, 57·6, 70·4 and 77·6% were obtained for cow, buffalo, sheep and goat, respectively.

Description: SUMMARYSix spring varieties of oats were sown in a glasshouse in winter and in spring. The grain was analysed for oil, protein and kernel content and 1000-grain weight, and the maturation period was measured.Oil content varied from 2·4 to 7·9% and protein content from 7·9 to 16·3%. Varietal differences in oil content between varieties were recognized and these were maintained at both sowing dates.Winter sowing, in comparison with spring sowing, resulted in an increase in oil and kernel content and 1000-grain weight, and a decrease in protein content. The increased oil content was partly due to increased kernel content, while the decrease in protein content was partly due to changes in 1000-grain weight.The maturation period was not affected by sowing date, but was positively correlated with oil content. Oil and protein content were not negatively correlated, and there were indications that it may be possible to select varieties which will produce grain high in both oil and protein.

Description: SUMMARYThe common use of range by different types of animals may be more efficient than separate grazing by each type in that they may be complementary in their utilization of forage. Also, under certain pasture and range conditions the danger of permanent damage by over-grazing can be critical. This paper presents a method of assessing the optimum carrying capacity of range under single or common use subject to constraints on the level of utilization of forage plants. The joint optimum carrying capacity for the animal types may vary as the management objective varies between maximum profit, maximum animal gain or maximum utilization of forage, all subject to the same protection against over-grazing.

Description: SUMMARYThe major nitrogenous components of gastric juice were determined in sheep with innervated pouches in the fundic and pyloric regions of the abomasum.Fundic secretions contained mean levels of 36–55 mg total-N/100 ml in the fluid fraction, and pyloric secretions contained 38–70 mg/100 ml. Of this, 65–76% and 75–91% could be attributed to protein, in the fundic and pyloric secretions respectively. Tungstic acid was found to be the most suitable precipitant of proteins in the gastric juice.Dissolved mucin accounted for 2–16% of the total-N in the fluid fraction of the fundic secretions, and for 6–14% in the pyloric secretions. Urea + ammonia contributed 2·8–13·4% of the total-N.The daily output of nitrogen by the fundic region of the abomasum, including that contributed by the cellular debris and visible mucus, was calculated at 0·46–2·4 g. The comparable values for the pyloric region varied between 0·05 and 0·37 g N/day.The electrophoretic patterns of the abomasal secretions were similar to those reported for human gastric juice.

Description: SUMMARYFifteen hundred Thornber 808 and 909 female chicks were reared for 126 days from day-old on conventional diets or on diets with 200 g field beans/kg. From 127 to 490 days they were offered a control diet or diets with 100 or 200 g field beans/kg. When the diets fed from 127 to 490 days contained 0 or 200 g field beans/kg their food intakes were 45·4 and 44·6 kg/bird and they laid 235 and 233 eggs, respectively. The differences were not significant. Efficiency of food conversion to egg mass was significantly reduced from 0·310 to 0·303 when beans were increased from 100 to 200 g/kg of diet and mean egg weight was significantly reduced from 58·9 to 57·6 g when beans were included at 200 g/kg of diet in the 127- to 490-day period.

Description: SummaryThree separate nitrogen balance experiments were made in three consecutive years. Comparisons of nitrogen retention were made between late-pregnant (15–20 weeks) Greyface (Border Leicester ♂χ Scottish Blackface ♀) ewes given a basal diet of hay and molassed sugar-beet pulp cubes (SBP, 1·25 em diameter x ca. 3cm length) and when given additional nitrogen supplied as urea contained in molassed sugar-beet pulp cubes (SBPU). Both sugar-beet pulp materials were adequately supplemented with minerals and vitamins. Supplementation with urea significantly increased nitrogen retention.

Description: SummaryThe frequency of natural crossing in 1972 was estimated, in two subsets of a composite cross grown in F6 in Nairn and in Fife, as 2·61±0·25% and 4·59±0·35% respectively. The estimated inbreeding coefficients of the parental generations were less than would be expected if all types of pollination were equally fertile and gave equally fertile offspring.

Description: SummaryThree field experiments are described in which the effect of plant density and date of stopping (removal of the apical bud) on the development of yield in several Brussels sprout cultivars was studied. In a fourth experiment, the effect of a leaf removal treatment was designed to assess the possible remobilization of dry matter to the buds from senescing leaves.A total plant dry weight of 1·2 kg/m2 was achieved with a hybrid cultivar at commercial densities. Although the crop growth rate was low in midsummer, growth continued until mid-October. Bud dry weight yield was curvilinearly related to plant density with 2 plants/m2 giving the highest yields of 0·35 kg/m2 in stopped crops in November. Rapid bud growth did not begin until September but the increase in bud dry weight continued into December and January. Early stopping increased bud dry weight yield and the ratio of bud weight to total shoot weight. In November, bud dry weight accounted for 25–40% of the total shoot dry weight for most treatments.In the leaf removal experiment, estimated net photosynthetic rate of the crop was greater than the bud growth rate up to the end of the experiment and there was no significant effect of removing leaves just prior to natural senescence on bud dry weight.The production and partition of dry matter is discussed in comparison with other vegetative crops. It is found that the proportion of total dry weight partitioned to the useful parts in Brussels sprouts is comparatively low. Factors controlling the date at which rapid bud growth begins are discussed. It is concluded that the dry matter in the axillary buds is derived from photosynthesis occurring at the time of bud growth and that the remobilization of dry matter from other plant parts is not of great importance.

Description: SummaryBlood samples were obtained at monthly intervals for 12 months from 8 HK and 8 LK wethers of the Marwari breed maintained at Jodhpur (26° 05′ N, 73° 01′ E). The samples were analysed for packed cell volume (PCV), red blood cell count (RBC), haemoglobin concentration (Hb), mean cell volume (MCV), mean cell haemoglobin concentration (MCHC), plasma inorganic phosphorus and plasma specific conductance.The HK animals, on average, had significantly higher PCV, RBC, Hb, MCHC and plasma inorganic phosphorus values than the LK animals but the MCV was significantly higher in the LK group. There was no difference in the plasma specific conductance.PCV, RBC and Hb values differed considerably from animal to animal within each group. These individual variations could help the breed to survive in a desert environment.No particular tendency or pattern in the effect of season on the blood characters studied has been observed. This indicates that the animals of both groups responded in a similar way to the environmental changes.

Description: SUMMARYMeasurements made on soils from the Ley–Arable rotation experiments and some of the Classical experiments at Rothamsted and Woburn are described. Values of exchangeable K, equilibrium activity ratio, equilibrium K potential, and buffer capacity are given for each plot. Potassium quantity/intensity relationships measured for each plot showed that no differences in K exchange behaviour have arisen as a result of manuring or of ley or arable treatments. The only fundamental variation was in the quantity of K in the soils. Continuous ley plots, whether given N fertilizer or containing clover, contained much more K than plots carrying crop rotations. In the Classical experiment soils, quantity of K depended largely on manuring.Potassium uptakes by ryegrass grown on the soils from the various plots are discussed. Potassium uptake was well-related to quantity of K, better so than to the other K parameters. The release of non-exchangeable K to the crop was non-linearly related to the fall in exchangeable K in the soils from the Rothamsted Ley-Arable experiments.Drying and re-wetting the cropped soils released K in amounts inversely proportional to the amount of K in the moist cropped soil. This release of K was unrelated to the original exchangeable K contents of the soils.

Description: SUMMARYA model is presented which considers the effects of competition between pairs of individuals in binary mixtures. Competitive effects are defined in terms of two parameters; a monoculture effect (Mo) which measures competition between like individuals and a mixture effect (Mi) which relates to competition between unlike individuals. If the data from a particular density replacement series conform to the proposed model the ratio of Mi to Mo can be used to determine whether it would be more advantageous to grow a mixture of the two components concerned or a pure stand of the better component. Where appropriate the optimal composition of the mixture may also be estimated. Theoretical considerations suggest that a 50:50 ratio only represents the optimal composition of a mixture when the two components possess a similar expression for the character concerned.The model has been applied to dry weight data collected over two growing seasons from a glasshouse experiment which contained 5 genotypes of Lolium perenne grown as monocultures and in all 10 binary combinations. Each combination was represented by three mixture proportions. For the majority of these density replacement series the model was satisfactory, with mixture effects tending to be of greater significance during the first of the two growing seasons. Failure of the model was in general due either to a specific form of competition, which maintained the performance of the mixtures at the level of the better monoculture, or to the presence of more complex forms of competition.The implications of this model for the development of productive herbage mixtures are briefly discussed, whilst the possible effects of invasion by unsown grass species upon the productivity of a pure sward are also outlined.

Description: SUMMARYDrying rates of stem internodes of S. 24 perennial ryegrass and S. 37 cocksfoot, some with leaf sheaths and laminae attached, were measured in controlled conditions of air speed, temperature and relative humidity after exposure for 60 sec to dry heat, steam, steam containing petroleum ether vapour, and petroleum ether vapour only. The last treatment was most effective in increasing the drying rate, but a similar effect was obtained by splitting the stem internodes longitudinally or by removing from the larger plant fragments (internodes with leaf) the leaf sheaths and laminae. Observations on leaves with a scanning electron microscope confirmed that the steam and petroleum treatments acted on the surface waxes thus reducing the cuticular resistance to water loss. The presence of internal tissue resistance was demonstrated by anaerobic treatment of ryegrass leaves and stem internodes to disrupt cell protoplasts. The ensuing increase in drying rate was clearest in stems which have a low surface area to volume ratio. The results suggest that the combination of both mechanical damage and thermal or chemical surface treatment could form the basis for more effective methods of increasing the drying rate in the field of crops cut for conservation.

Description: SUMMARYDigestibility, performance and carcass analysis trials were used to compare the nutritive value of two diets, containing 78% of either cooked potato flake (diet CPF) or maize meal (diet M). Diet CPF had slightly lower values for gross energy (GE) and nitrogen (N), markedly lower values for ether extractives and crude fibre, a slightly higher lysine concentration and a markedly higher potassium concentration.Apparent digestibility coefficients were determined with ten piglets weighing 22 kg; digestibility values for GE and N were respectively 0·95 and 0·91 for diet CPF, and 0·84 and 0·88 for diet M. Digestible energy (DE) and digestible N (DN) values were 10·2 MJ and 26·9 g/kg dry matter for diet CPF, and 15·3 MJ and 27·9 g/kg dry matter for diet M. The performance of 30 piglets grown from 21 to 53 days of age and from 6·0 to 13·1 kg was similar for each diet, as were the empty body, water, N, lipid, ash and GE gains of 18 of these piglets. The efficiencies of conversion of nutrients ingested from diet CPF into the components of body gain were for GE, DE, N and DN; 0·21, 0·22, 0·48 and 0·52 respectively. Corresponding values for diet M were 0·17, 0·21, 0·38 and 0·44.The greater efficiency with which the nutrients in the potato flake were used thus resulted in a growth response which was at least equal to that of the maize meal.

Description: SUMMARYA technique is described for the in vivo estimation of the rate of production of bacteria in the rumen of buffalo calves. The animals were given their daily ration in 12 equal amounts at 2-h intervals. The bacterial cells from the rumen were labelled either with 14C or 36S by in vitro incubation in the presence of [U-14C]DL-leucine or 35S-sodium sulphate. Labelled bacterial cells were injected in a single dose into the rumen. Samples of the ruminal fluid were drawn at various time intervals for 9 h and the specific radio-activity of the bacteria determined. The dilution in the specific radioactivity was used to calculate the turn-over time and rates of production of bacteria in the rumen. The average turnover time was 308 min. The production rate of bacteria averaged 211 mg/min (20·3 g/mole VFA produced).

Description: SUMMARYIn 92 field experiments in Tanzania's major cotton-growing area south and east of Lake Victoria mean yield without fertilizer was nearly 900 kg/ha of seed cotton. The mean direct effect of 224 kg/ha of single superphosphate with 202 kg/ha of ammonium sulphate was 380 kg/ha of seed cotton; with twice as much fertilizer the increment was 525 kg. First and second residual responses made important contributions to the total effect of superphosphate. In most zones the response to each fertilizer was large but in Nassa response to superphosphate was small; in Nzega yields were small and there was no response to ammonium sulphate, perhaps because Calidea dregei caused abscission of bolls; on the acid soils of Ukerewe Island yields and responses to superphosphate were small.Data are given to show the average amounts of plant nutrients in the soils most used for cotton. Correlations of yields with soil chemical data suggest that some soils lack enough calcium for large yields. A long-term experiment at the Ukiriguru research farm (Le Mare, 1972) showed that productivity of impoverished soil growing cotton every year was recovered and improved by lime with phosphorus and nitrogen fertilizers: the experiments throughout the cotton area indicated that those results were widely relevant.

Description: SUMMARYThe wool weight/m2 of LK progeny arising out of LK × LK matings (approximately a quarter were HK and were excluded) and HK progeny arising out of HK × HK matings (all were HK) of two coarse-wool producing breeds of sheep, Marwari and Magra, were compared with the mid-parent values. LK progenies produced significantly more than the mid-parent value in both the breeds, but there was no increase in HK progeny. The difference in wool weight between the HK progeny and their mid-parent value tended to be less for Marwari whereas it was much less for Magra breed.The results suggest that improvement in wool weight of sheep can be made by maintaining LK stock and mating LK × LK, culling the HK arising out of these matings in each generation.

Description: SUMMARYThe possible adaptive significance of the occurrence of HK and LK red-cell types in Murrah buffaloes was investigated. Judged by haematological indices and thermorespiratory responses under conditions of moderate thermal stress, LK animals appeared to have a greater adaptive potential than HK animals in a hot arid environment. Dry matter percentage, packed cell volume (pcv), haemoglobin concentration (Hb), red blood corpuscles (RBC) and plasma protein values were significantly higher in LK-type animals. In addition, under identical conditions of thermal stress the LK animals exhibited significantly less rise in rectal temperature and respiratory rate than the HK animals.

Description: SUMMARYIn two experiments frozen heather (Calluna vulgaris, L. Hull), which contained 85–90% of the current season's shoots, was offered ad libitum to castrated male sheep. In one experiment, heather harvested in July, September, November and March was offered to six sheep per harvest, D.M. digestibility fell from 55.9% in July to 41.9% in March, with the greatest decline occurring after flower development in August. There were no significant changes with season in voluntary intakes, which were low, ranging from 29 to 39 g D.M./kg W0.75/day. Apart from the July harvest, intakes of digestible D.M. were insufficient to maintain the sheep. The apparent digestibility of N(14·3–42·2%) and plasma urea N values (5–6 mg/100 ml) were low and undigested N of dietary origin in the faeces was high (25–45%). Sheep offered the September, November and March harvests were in considerable negative apparent balances of N and it was calculated that the sheep were in a negative balance of truly digested N. In a second ex-periment, heather harvested in August from pioneer, building and mature stands was offered to six sheep per harvest. There were no significant differences between stands in voluntary intake and digestibility.

Description: SUMMARYIn simulated swards of perennial ryegrass the production of aerial tillers, in which the growing point has been raised some distance above ground level by internode extension, depended upon the genotype and management. In both genotypes studied decreasing the height of defoliation from 10 to 2·5 cm nearly halved the incidence of aerial tillering, while the presence of a mulch of chopped straw at the base of the sward more than doubled the occurrence of these tillers. The effects of management are also discussed in relation to herbage production. The differences between the genotypes in the degree of aerial tillering suggests that selection for reduced aerial tillering may be of benefit.

Description: SUMMARYA trial to compare the reliability of yield of a quick maturing maize (Taboran) with the medium maturity local maize was carried out at two low rainfall sites in Southern Province, Kenya, from 1957 to 1961. Each variety was grown at two spacings, giving plant densities of 1·8 and 3·6 pl./m2. Results showed a consistent difference in ‘days to 50% silking’, Taboran being on average 17 days earlier than Local White. There was no overall difference between varieties or spacings in yield per ha. There were highly significant interactions of seasons with varieties and with spacings. These were interpreted in terms of different linear yield/rainfall relationships for each variety and each spacing. A variety/spacing interaction was also demonstrated.Analysis of components of yield showed that similar linear relations between rainfall and each yield component obtained. There were significant differences between varieties and between spacings in both mean number of cobs per plant and yield per cob. Taboran had a higher mean number of cobs per plant and Local White a higher mean yield per cob. Seasons x varieties interactions were again interpreted in linear regression terms. Earliness of the Taboran variety often enabled plants to produce silks before development was arrested by drought and so was responsible for its relatively high mean number of cobs per plant in low rainfall seasons, giving it an advantage over Local White in yield per unit area in such circumstances. Taboran was shown to have a potential value in local agriculture, because of its consistency of yield. The expected advantage or disadvantage of Taboran over Local White was calculated for an area of known rainfall from the respective yield/rainfall regressions and the seasonal rainfall probabilities.Selection for earliness was shown to be of basic importance in a breeding programme for the low rainfall areas. Within a specified early maturity range, selection for yield improvement through the yield per cob component could be practised. A maturity length similar to Taboran would ensure a high value of mean cobs per plant in low rainfall season, i.e. confer the necessary reliability of yield.

Description: SUMMARYSteers fed low nitrogen diets were infused intraruininally with water.Increasing the water load increased the urine volume and urinary urea excretion and depressed the plasma urea level.The effect of intraruminal water loading was studied in association with intravenous urea loading of 25 and 65 g N/day. When 25 g N/day as urea was infused intravenously, water loading did not significantly increase the urinary urea excretion but the plasma urea level was depressed. At 65 g N/day water loading increased the urinary urea excretion and decreased the plasma urea level.Significantly different relations between plasma urea and urea load existed for the ad lib. water and the water-loaded treatments but the relation between rumen ammonia level and plasma urea level was not affected by the water loading.The results are discussed with reference to the recycling of urea.

Description: SUMMARYThe growth patterns of impetus groups of muscles were mostly not significantly affected by rate of growth of the musculature. One small group – the low/average impetus muscles – had a significantly lower ‘b’ value in the calves fed at a high plane. It appears that under differences of feeding encountered commercially, no changes of practical importance in the relative growth of muscles are likely to be produced which are attributable to rate of growth of the musculature.

Description: SUMMARYThe growth and yield of three tropical varieties of maize were studied at two elevations in Mexico: Poza Rica (60m) and Tlaltizapan (940m). Grain yields were between 3·5 and 8·5 t/ha. The growing period was longer and the crop produced more dry weight and yield at Tlaltizapan than at Poza Rica. Crop growth rates (C) increased to a maximum of about 35 g/m2/day at both sites and then declined. Grain growth rates (maximum 35 g/m2/day) exceeded current C during most of the grain filling period. After silking when C exceeded grain growth, dry matter accumulated in the stem. Later as grain growth increased and exceeded C, some of the accumulated material was incorporated into the grain and stem weight decreased. The dry weight increase after flowering was similar at the two sites, but the grain yield at Tlaltiapan was larger because a larger proportion of the dry weight increase was incorporated into the grain than at Poza Rica. The results indicate that at both sites grain ‘sink’ capacity was limiting yield.

Description: SUMMARYCalves were slaughtered at predetermined weights after being fed individually on fresh and reconstituted whole milk at three levels. The highest level of feeding was ad libitum and the lowest was aimed at keeping the calves at their birth weight for 72 days before providing extra milk to allow growth to proceed.Dressing percentage did not decline with age as it did in a previous experiment using roughage in the diet. The faster-grown calves had a higher dressing percentage. It is concluded that both rate of growth and the physical nature of the diet influenced dressing percentage.Muscle: bone ratio and the amount of fat and bone in the carcass were not significantly affected by the rate of live-weight increase.

Description: SUMMARYDistribution of red cell potassium in buffaloes and its possible genetic control was investigated. The mean values of red cell K+ varied between 37 and 41 m-equiv/l in LK type animals and between 87 and 91 m-equiv/l in the HK type. Red cell K+ concentration within individual animals of either LK or HK type was fairly stable over successive samplings, whereas the same values among animals within a type varied rather widely. The inheritance of red cell K+ type in buffaloes appeared to be controlled by a single pair of genes. HK animals were homozygous for the recessive allele while LK animals represented the heterozygotes and also the homozygotes for the other allele. In addition, there was indication that the gene responsible for LK phenotypes might not be completely dominant over the recessive allele. The three populations of buffaloes examined were found to be in genetic equilibrium in respect of red cell K+ polymorphism. HK animals predominated in both the breeds, the frequency of the recessive gene (h) being 0·78 and 0·74 for the Murrah and Bhadawari breeds respectively.

Description: Two field experiments were conducted in 1971–72 and 1972–73 on two similar sites of calcareous clay soils (vertisol) with paste pH 8·2, 0·024% and 0·22% organic carbon. Wheat (Triticum aestivum L. var. (LR N10) An3) was grown and the fertilizers ammonium sulphate, urea, nitrophoska 15% N, 15% P2O5, 6% K2O), calcium nitrate (Ca NO3)2·4H2O) and ammonium sulphate nitrate were each used at 70 kg N/ha at seeding, tillering, jointing or ear emergence and there was one treatment with no N fertilizer. The treatments were arranged in a randomized block design with four replications. Each plot was 6·0 x 7·0 m of which 4·0 x 5·0 m was harvested. N fertilizers were broadcast by hand and no basal potassium or phosphorus were added since they are known to have no effect on wheat yield on these soils. Seed a rate equivalent to 85 kg/ha was weighed separately for each plot and sown by hand in rows spaced 20 cm apart. Each experiment received 10 irrigations, each equivalent to a head of 10 cm of water, at 10-day intervals.

Description: SUMMARYHens and cockerels of a White Leghorn strain (‘H & N’) were kept at a constant temperature of 23 °C from 1 year until 2¼ years of age. The mean fasting heat production, which was measured 6 times during this period, varied between 404 and 464 kJ/kg0·75/day for the hens and between 223 and 349 kJ/kg0·75/day for the cockerels. The sex difference in heat production is discussed and an attempt is made to explain the variation in heat production for each sex.

Description: SUMMARYFactors which could be expected to influence levels of ammonia in the rumen were compared in sheep maintained on diets providing 11·4 or 20·7 g N/day.The ruminal fluid volume in sheep given the lower-N ration was 78% of that in sheep maintained on the higher-N diet. The effect of this in diluting rumen ammonia from recycled urea is discussed.Ruminal urease activity was higher in sheep given the lower-N diet, and was confined to the particulate fraction of rumen liquor in animals given either diet. At least 95% of the maximum activity occurred in the range of pH 5·4–7·05, and pH 6·0–7·25 in sheep maintained on the lower- and higher-N diets respectively. Small variations in activity were observed between the morning and evening meals.In vitro rates of net ammonia production in samples of rumen liquor were similar in sheep given either diet; a positive correlation with the initial ammonia concentration was evident. Net utilization of ammonia was detected in some experiments in samples from sheep maintained on the lower-N diet. Starvation for 1 day was associated with increased rates of production and initial concentrations of ammonia.Cellulose, as cotton thread, was digested at similar rates in vivo in sheep given the different diets. This is discussed in relation to the demand for ammonia by cellulolytic bacteria.

Description: SUMMARYThe effect of single, intravenous injections of urea on the concentration of ammonia in the rumen has been examined in conscious and anaesthetized sheep.In conscious sheep maintained on a diet providing 11·4 g nitrogen/day, the net increase in concentration of rumen ammonia after the injection of urea showed negative correlations with the pre-injection concentrations of rumen ammonia and of plasma urea. The maximum concentration of ammonia attained in the rumen after the injection wasx 16·6 ± 0·28 mg NH3-N/100 ml. No such correlations were found in conscious sheep given a diet providing 20·7 g N/day. In addition, the maximum concentration of ammonia attained in the rumen after the injection of urea was significantly lower at 10·7 ± 0·91 mg NH3-N/100 ml, and the net increases in concentration were smaller.Starvation for one day reduced the net increment in rumen ammonia concentration after urea injection in animals given the lower-N diet, to the same low level observed in fed or starved sheep maintained on the higher-N diet.Differences were observed in the transfer of blood urea to the rumen in experiments with anaesthetized sheep which had been maintained on the lower-N diet for long or short periods beforehand. Animals which had been left to graze, and then housed indoors and given the lower-N diet for a short period before the experiment, showed much smaller increases in rumen urea plus ammonia concentration after the injection of urea than sheep which had been given the same diet for a long period. There was no difference in the response of the salivary secretions to the urea injections.

Description: SUMMARYThe genetic control of the level of reduced glutathione (GSH) in the erythrocytes of pure bred Australian Merino sheep has been investigated. The data suggest that the erythrocyte GSH levels are in part controlled by a single pair of autosomal alleles, the gene for GSH-high (GSHH) being dominant.The data also suggest that the levels of erythrocyte GSH within the GSH-high and GSH-low types are the result of polygenic influences. Heritability estimates of 0·7 and 0·5 within the GSH-high type and 1·2 in the GSH-low type support this suggestion.

Description: SUMMARYThe effectiveness of certain pesticides a ainst adults and eggs of Tetranychus cinnabarinus Boisduval infesting cotton was sti died. Kelthane S and Rogor gave the best performance in the field evaluation, whilu Kelthane, Dursban and Cyolane were best in the laboratory evaluation. Specific acaricides were generally more toxic than the other insecticides on both adults and eggs of the mite. The slide-dip method was more sensitive for testing Kelthane, Dursban and Cyolane.

Description: SUMMARYPublished data are used in support of a hypothesis that equal amounts of digestible cell walls and digestible non-cell walls do not contribute equally to the energy value of forages. The relationship between the concentration in the organic matter of metabolizable energy (kcal/g organic matter) determined at the maintenance level of feeding, and the percentages of cell wall and digestible cell wall in the forage organic matter is defined by:This equation derived from published data on 12 grasses appears to be applicable to both grasses and legumes.

Description: SummaryPreharvest sprays with 6-hydroxy-3-(2H)-pyridazinone (MH), or immersion in solutions of MH, 2,4-dichlorophenoxyacetic acid (2,4-D), 2-chloroethylphosphonic acid (ethephon), coumarin or (2-chloroethyl) trimethylammonium chloride (CCC) inhibited both sprouting and rooting of treated carrots during storage at 0 °C whencompared with water-dipped or untreated carrots, while N-6-benzyl-adenine (BA) dips stimulated extensive rooting and sprouting. In contrast, immersion in gibberellic acid (GA3) solutions had very little effect.Storage atmospheres containing 1, 2.5, 5 or 10% oxygen inhibited both sprouting and rooting but increased mould infection. Atmospheres containing 21% (air) or 40% oxygen reduced mould infection, but increased sprouting and rooting of stored carrots. Washing carrots in water before storage did not significantly affect mould infection, while washing in 0.5% clorox increased it. However, washing in water followed by immersion in MH inhibited both sprouting and rooting and also reduced mould infection. ‘Jumbo’ and large-size carrots stored better than medium and small carrots.

Description: SUMMARYThe growth and development of two semi-dwarf winter wheat varieties, of two taller varieties, and of random selections from two crosses between semi-dwarf and taller varieties were compared over 2 years. Changes with time of crop dry weight/m2, leaf area index and ear size were expressed as orthogonal polynomial regression coefficients. Significant correlations were obtained between yield, the polynomial coefficients and growth measurements relating to number of tillers and flag leaf area duration, but many of these variables were significantly correlated with each other. Multiple regression equations were therefore calculated expressing yield in terms of the variables. These showed flag leaf area duration and rate of ear growth to be the most important characters determining crop yield. The greatest reduction in total yield variance was obtained by the simultaneous consideration of characters relating to photosynthetic capacity and ear development. The significance of this finding in relation to the relative importance of ‘apos;source’ and ‘sink’ in determining grain yield are discussed.

Description: SummarySheep prepared either with a rumen cannula, or with a rumen cannula plus re-entrant cannulae in the duodenum and ileum were fed fresh ‘Ruanui’ perennial ryegrass (R), ‘Manawa’ short rotation ryegrass (M) and white clover (C) at dry-matter intakes ranging from 450 to 1000 g/24 h. Paper impregnated with chromic oxide was given once daily via the rumen fistula as a marker.Amounts of non-ammonia-nitrogen (NAN) entering and leaving the small intestine and nitrogen (N) excreted in the faeces were regressed against the intake of N for each sheep and these equations (all significant P 〈 0·05) were used to calculate the extent of digestion in the stomach, the small intestine and the large intestine at two levels of OM intake (500 and 800 g daily). Amino acid analyses of feed and digesta samples are also presented together with calculations of the apparent absorptions of individual amino acids from the small intestine.At an intake of 500 g OM amounts of NAN entering the small intestine were significantly greater (P 〈 0·05) in sheep given M than in sheep given R or C. At an intake of 800 g OM amounts in sheep given M were significantly greater (P 〈 0·01) than in sheep given R. NAN leaving the small intestine and N excreted in the faeces were similar for all three diets.At an intake of 800 g OM apparent absorptions of NAN from the small intestine of sheep given M (0·47 × N intake + 2·8 g/24 h) and sheep given C (0·51 × N intake – 1·3 g/24 h) were significantly greater (P 〈 0·01 and P 〈 0·05 respectively) than of sheep given R (0·41 × N intake – 0·5 g/24 h). As intake of herbage was increased the partition of digestion altered.Only small differences between herbages were found in the amino acid composition (g amino acid/100 g protein) of either duodenal or ileal digesta, but because of the large differences in the flows of NAN, the apparent absorptions of individual amino acids from the small intestine were much higher in sheep given M than in sheep given the other two species.The results are discussed in the light of available information on sites of digestion of herbage diets in sheep.