ALBERT

Description: Three experiments were carried out to obtain more information upon the effects of varying the plane of feeding for bacon pigs.Exps. 1 and 2 followed the same 3 × 2 factorial design in which (a) diets were fed with or without procaine penicillin and (b) a comparison was made between very high (VH-VH), high (H-H) and low (L-L) planes of feeding for pigs from about 8 weeks old to slaughter at about 200 lb. live weight. The planes of feeding were defined according to the amount of t.d.n. offered to each pig daily.For each of these two experiments eight lots of six litter mates were used. One pig from each litter was allocated to each of the six treatments, and although litter mates were housed as a group, all pigs were fed individually in separate compartments.Exp. 3 was a 2 × 3 × 2 factorial to compare two breeds and three planes of feeding during 2 years. During each year three lots of pure-bred Landrace and three lots of Wessex Saddleback × Large White litter mates were used. Each lot consisted of three gilts and three barrows and one pig of each sex was allocated to each of the three feeding treatments. From the start of the experiment, when the pigs were about 8 weeks old, to about 100 lb. weight, all animals were kept to a very high (VH) plane of feeding. From then to slaughter at about 200 lb. live weight the following planes of feeding were compared: (1) very high plane (VH), (2) increasingly restricted plane (R) and (3) low plane (L). As in Exps. 1 and 2 these planes were denned in terms of t.d.n., and litter mates were housed together but fed individually in separate compartments.In both Exps. 1 and 2 pigs with procaine penicillin in their feed grew very slightly faster and more efficiently than those not fed antibiotic, but the differences did not reach the 5% level of statistical significance. The feeding of antibiotio did not affect the response of the pigs to variations in the plane of feeding.In comparison with pigs kept to the VH-VH plane of feeding, pigs kept to the H-H and L-L planes grew 13 and 22% more slowly in Exp. 1, and 11 and 26% more slowly in Exp. 2, but plane of feeding had no effect upon food conversion efficiency in either experiment. These results are for the total experimental period.In both Exps. 1 and 2 reductions in plane of feeding had no significant effect upon length of carcass or thickness of streak, but they caused increases in killing-out percentage and decreases in all measurements of fat thickness. They also caused increases in the area of ‘eye’ muscle (statistically significant in Exp. 2, but not in Exp. 1) and a lengthening in the shape of the ‘eye’ muscle in the bacon rasher (statistically significant in Exp. 1, but not in Exp. 2).In Exp. 3 the Wessex crosses grew faster and more efficiently than the Landrace, but these differences were considerably larger during one year than during the other. In comparison to the Landrace, the Wessex-cross carcasses had a tendency to be shorter (P 〈 0·10) and to have thicker shoulder fats. They also had 1% more ‘fore’ and 1% less ‘ham’.Compared with pigs kept to the VH-VH plane of feeding, those kept to the VH-R and VH-L planes grew 18 and 36% more slowly, respectively, during the finishing period. Over the total experimental period there was no difference in food conversion efficiency between pigs kept to the VH-VH and VH-R planes, but efficiency was poorer by 4–5% with the VH-L plane. There was no breed × feeding interaction in the data for growth rates or food conversion efficiencies.In Exp. 3 plane of feeding had no significant effect upon killing-out percentage, shape index of ‘eye’ muscle or thickness of streak. The two lower planes of feeding caused reductions in the average rump fat, fat (1) over the ‘eye’ muscle and in the proportion of ‘middle’ in the carcasses; they also caused increases in the proportion of ‘ham’ in the carcasses.Other carcass quality data contained significant interactions which complicated their interpretation. The effects of plane of feeding were inconsistent between:(A) years, for length of carcass, maximum shoulder fat, area of eye muscle and iodine values of the back fat;(B) breeds, for minimum back fat and percentage ‘fore’;(C) sexes, for dressing percentage and fat (2) over ‘eye’ muscle;(D) breeds and years, for dressing percentage;(E) breeds and sexes, for maximum shoulder fat.The results of the three experiments have been compared with other data on planes of feeding from Rowett Research Institute. A table has been given showing the probable average effects of using different planes of feeding in preference to a VH-VH plane for pigs to be slaughtered at about 200 lb. live weight. The variability in these effects under different circumstances has been discussed and a note has been made of the relative improvements in carcass quality which can be affected through feeding and through breeding.

Description: 1. An experiment was conducted to study the effects of progesterone and pregnant mare serum (p.m.s.) on incidence of oestrus, macroscopic changes in the ovaries, histological appearance of the genital tract, the vaginal smear and cervical mucus of New Zealand Romney Marsh ewes in deep anoestrus. Ten animals served as controls, thirty-five received progesterone daily for 4–12 days and ten were given p.m.s. alone. The remaining fifteen ewes were treated with progesterone for 4–6 days followed by p.m.s.2. In ewes treated with progesterone alone, neither ovulation nor oestrus resulted. After p.m.s. alone six animals ovulated, while injection with both hormones caused ovulation in all 15 ewes and one was in oestrus.3. Sections cut from the mid-region of the fallopian tube, uterine horn and cervix were examined. Histological responses to progesterone and p.m.s. were found in all positions of the tract and were greatest in the ewes which had ovulated.4. In the ewes which ovulated a sequence of macroscopic and microscopic changes occurred in the vagina and these seemed similar to those associated with ovulation during the oestrous cycle.5. Crystallization patterns in cervical mucus were seen in some ewes of all groups. Accompanying ovulation the phenomenon was seen for several days but was absent during most of the luteal period. When no follicles ruptured cervical mucus patterns often persisted. In most cases the presence and absence of arborization was presumably related to follicular oestrogen and progesterone from an induced corpus luteum and was in similar time relationship to that normally accompanying ovulation in the oestrous cycle. Some inconsistency in the response of cervical mucus following hormone treatment was noted.6. No evidence was found that hormone treatment had initiated a regular cycle of ovarian activity.

Description: The effects of copper supplements on the performance up to 45 lb. live weight of early weaned pigs were measured in two experiments. Copper sulphate included as 0·1% of the diet had no apparent adverse effect on the piglets, even when it was introduced immediately after weaning at about 8 lb. live weight, but improved rate of gain by 6 and 12% and feed conversion efficiency by 5 and 6% in the two experiments, respectively. The length of the period of slow growth after weaning was reduced in both experiments. There was no clear advantage in delaying the introduction of the high-copper diet until the pigs weighed 17 or 26 lb.The second experiment was a 2 x 2 factorial, the second factor being the presence or absence in the diet of antibiotic (present throughout in the first experiment). Antibiotic appeared to have slight beneficial effects on growth rate and feed conversion, which were additive to the effects of copper so that the best results were obtained from the diet containing both copper and antibiotic.In a continuation of the first experiment it was found that the early copper treatment had no effect on rates of gain and feed conversion between 55 and 200 lb. live weight or on carcass measurements. The inclusion of a copper supplement in the diet from 55 to 200 lb. improved feed conversion by 4% and rate of gain by 3·5%, reduced the thickness of streak and increased the ratio of width to depth of eye muscle. None of these responses was affected by the copper treatment prior to 55 lb. live weight.

Description: 1. A 36-day continuous digestibility trial with three steers and three sheep fed fresh pasture herbage was carried out during May and June, 1960. For all animals the digestibilities of herbage organic matter (O.m.) were estimated both by collection of faeces and by administering standard quantities of chromium sesquioxide (Cr203) twice daily and determining concentrations of Cr203 in faeces. In a further 36-day trial during August and September 1960, three steers and three cows were used; with the steers, digestibilities were estimated by both methods but with the cows by the Cr203 method only.2. Regression equations were obtained relating O.m. digestibility to the percentage of nitrogen (N) in faecal O.m. When digestibilities were estimated by the same method the same regression coefficients could be fitted to the data from each of the steers and sheep in the spring trial. A similar result was found with the data from each of the steers and cows in the summer trial.3. In each equation different constant terms were required for each animal, which differed significantly between individuals but not between species or class of animal. Data obtained from an examination of the relationship of g. N excreted per 100 g. feed dry matter to g. N intake per 100 g. feed dry matter indicated that differences between the constant terms could be linked with variations between animals in the excretion of metabolic faecal N.

Description: 1. A mixed sward was divided into two areas receiving high (H) or low (L) levels of fertilizer nitrogen, and on two occasions, in spring and summer, herbage cut from each area was given to three steers in a continuous digestibility trial lasting 45 days. Digestibility and faecal nitrogen concentration were measured for each animal for each 24 hr. period, and equations relating these variables were calculated for each trial from the unit 24 hr. observations and from averages over three animals and over successive 2-, 3-, 5- and 9-day periods.2. In the two spring trials herbage digestibility remained constant for the first 12 days and then declined by about 0·4 units per day. In the summer trials digestibility declined throughout by 0—25 units per day. The nitrogen content of the herbage was consistently 25% higher for treatment H, and declined steadily throughout each trial.3. Both season of cutting and fertilizer treatment had a significant effect on the faecal index regressions obtained. Equations calculated from average values for three animals and 3 days predicted digestibility coefficients from 3% faecal nitrogen as follows: equation (1) spring H, 76·5; (2) spring L, 77·5; (3)summer H, 71·8; (4) summer L, 72·8.4. The joint residual standard deviation for equations (1) to (4) had the low value of ± 0·90 units of digestibility, indicating that ‘single-sward’ regressions are considerably more accurate than those embracing a great variety of herbages. Even greater accuracy was obtained when digestibility and faecal nitrogen concentrations were measured for periods longer than 3 days; in general, residual variance varied inversely with period length. Using values for individual animals in the regressions increased the residual variance slightly, but because differences between animals in the digestibility-faecal nitrogen relationship were small and generally nonsignificant, the increase was by a factor of the order of 1·6, not 3.5. Standard errors of prediction were calculated, although there is evidence to suggest that these underestimate the error of digestibility coefficients predicted for free-grazing animals. It is concluded that faecal index regressions are accurate enough for measuring digestibility per se in grazing experiments. In the measurement of herbage consumption, however, the experimental error is likely to be high, partly because indigestibility is the factor required to be predicted, but mainly because of large differences in appetite among similarly treated animals.