ALBERT

Description: The Mackenzie River is the seventh longest river in the world and with its tributaries drains a million sq. miles of northern Canada. Its drainage basin includes almost all of that portion of the District of Mackenzie lying south of the so-called “tree line”, two large sections of Yukon Territory and portions of the provinces of Saskatchewan, Alberta, and British Columbia. When flying from Fort Smith, lat. 60° N., to Inuvik near the Arctic Ocean it seems to be an endless expanse of swamp and tundra with almost no possibilities for logging, either now or in the future. Closer inspection, however, shows that there are forested areas capable of supplying timbers suitable for lumber and heavy construction, as well as poles for piling and mining timbers. It is with these forests that this article is primarily concerned.

Description: SUMMARYThirty-six mature Finnish Landrace × Dorset Horn ewes, each suckling two lambs, were used in a comparative slaughter experiment to measure changes in body tissues during early lactation. Two levels of body fatness at lambing were established by giving ewes a complete diet containing 10 MJ metabolizable energy (ME) and 139 g crude protein (CP)/kg d.m. either close to requirements or ad libitum during the second half of pregnancy. In lactation half the ewes in each group were given a complete diet containing either 90 (diet A) or 60 (diet B) % milled hay ad libitum. These diets contained 7·9 and 9·2 MJ ME and 121 and 132 g CP/kg d.m. respectively.Ewes fed at the two levels in pregnancy contained 8·4 and 19·6 kg chemically determined fat 5 days after lambing but had similar amounts of body protein, ash and water. Over 6 weeks of lactation ewes given diet A lost 60 and 69% of these weights of fat respectively, while ewes given diet B gained 5% and lost 30% respectively. Up to 26 g of body protein was lost daily from ewes given diet A but none from ewes on diet B. During early lactation the weight of the empty digestive tract increased while the weights of most other body components, particularly the carcass, decreased. The ratio of body energy change to live-weight change varied from 24 to 90 MJ/kg. Thus live-weight change did not accurately reflect relative or absolute changes in body energy.Voluntary food intake was greater for ewes given the high-energy diet (B) than for those given diet A and was depressed in the fatter ewes. Differences in intake could be explained by the effects of body fatness and diet on the weight of gut contents. Milk yield was not significantly affected by body fat reserves but was higher on diet B than A. Fat content of milk was higher and protein content lower for ewes with the higher fat reserves at lambing.As the contribution of fat loss to energy available for milk synthesis increased there appeared to be a reduction in the energetic efficiency of milk synthesis. A number of possible reasons for this are discussed.

Description: SUMMARYThe efficacy of estimates of gut contents and total body water in increasing the precision with which the chemical composition of the body could be estimated in early lactation was evaluated in 36 Finnish Landrace × Dorset Horn ewes. The ewes were fed at two levels in pregnancy, and, in lactation, given diets of two metabolizable energy concentrations.The allometric relationships relating weight of chemical fat and protein to emptybody weight were not affected by treatment or stage of lactation. Inclusion of an index of gut contents, based on dry-matter intake, indigestibility and retention time of food residues, together with live weight in a regression equation predicting weight of body fat, only slightly increased the precision of estimate compared with equations using live weight alone.There was a close negative relationship between the proportions of water and fat in live weight. Inclusion of weight of body water with live weight in a regression equation predicting weight of body fat markedly increased the precision of estimate and the residual error (0·81 kg) was similar at different stages of lactation. However, when deuterium oxide space was used instead of body water there was only a small increase in precision of estimate and the residual error varied from 5·3 kg in early lactation to 2·1 kg in mid-lactation. The relationship between deuterium oxide space and body water was shown to be variable and altered by stage of lactation, and these differences were associated with differences in rate of water turnover in the animal's body.It is concluded that estimates of body water are unsuitable for estimating weight of body fat in early lactation.

Description: The work reported in two previous papers, Robinson (1960a, b) led to certain conclusions which required evaluation in terms of coffee yields (Coffee arabica Linn). The work describes changes in nitrate and ammonia-N in the Kikuyu red loam coffee topsoil, both natural and fertilizer derived, in the presence and absence of mulches.This paper presents early coffee yield results which have been obtained from field trials laid down on the Coffee Research Station, Ruiru, Kenya, to measure the effect of treatments based on the conclusions drawn from the soil studies.

Description: 1. Evidence is presented to show that compared with an unmulched soil, a surface mulch reduces the nitrate-N levels significantly following an application of a nitrogen fertilizer during the rains.2. Natural nitrate-X values in the top-soil were lower under a gravel mulch than a Napier grass mulch. It is concluded that the effect of a Napier grass-mulch cover in lowering natural soil nitrogen-N is offset in part by nitrates formed from the nitrogen it contains.

Description: 1. The general seasonal trends of top-soil nitrate and ammonia-N, and growth of the coffee tree are described for conditions of both soil and climate which are representative of a large proportion of the coffee-producing area in Kenya.2. When rainfall is heavy and persistent at the beginning of a rains period soil nitrate-N levels decrease rapidly, partly because of leaching losses and partly through uptake by the crop. Under conditions of rainfall and cropping similar to those described for the first half of 1954, the flush of nitrate-N in the early part of the rains will not be detected under field conditions. When the onset of the rainfall season is more gentle and substantial water movement through the upper part of the soil profile does not take place, for example, Short Rains, 1954, nitrate-N values do not decrease rapidly and there is indirect evidence of the stimulatory effect of this type of rainfall on nitrate-N formation in a remoistened field soil.3. Rapid and substantial build-up of nitrate-N is shown to take place during intervening dry weather between the rainfall periods. This is particularly marked in the top 6 in. of the soil profile and is attributed to nitrate-N formation in the absence of leaching losses; to a decreased rate of uptake by the coffee tree in the absence of vigorous growth and to the physical movement of nitrate-N upwards into the top-soil.It may be inferred from the results that alternate periods of rain and sunshine, rather than continuous heavy rain, will favour high soil nitrate-N levels and a more satisfactory nitrogen nutrition of the coffee tree.4. During periods of very low soil moisture ammonia-N builds up in the dry top-soil.5. The sharp peak and rapid decline in the rate of coffee growth during the Long Rains period coincides with very low soil nitrate-N values although climatologically conditions for continued growth are still excellent. This suggests that low available soil nitrate -N may be at least partially responsible for this early and rapid decline in the growth rate.6. In the light of observed trends in nitrate-N and coffee growth the timing of fertilizer nitrogen application to mature coffee has been altered. During the Long Rains split applications are recommended with the particular object of maintaining a supply of readily available nitrate-N in the soil. An additional and supplementary fertilizer nitrogen application is also suggested in the Short Rains period.

Description: SummaryEstimates of the energy contents of the foetuses, placentae, foetal fluids, empty uteri and maternal empty bodies at 88 and at 144 days of pregnancy were obtained from a comparative slaughter experiment on Finnish Landrace × Dorset Horn ewes. Over this period the mean daily intakes of metabolizable energy (ME) for ewes with twin, triplet or quadruplet foetuses were 11·2, 12·0 and 12·2 MJ respectively (low plane of feeding) or 14·4, 15·2 and 15·3 MJ (high plane of feeding), total numbers of ewes being 15, 23 and 7 respectively. The diet contained 8·2 MJ of ME and 153 g crude protein per kg dry matter. All six categories of ewe lost energy from maternal empty-body tissues between 88 and 144 days at mean daily rates of 2·7, 4·1 and 4·9 MJ (low plane) and 1·4, 2·7 and 3·6 MJ (high plane), according to litter size. Rates of energy deposition in the gravid uterus were 0·72, 0·93 and 1·07 MJ/day respectively, and were not affected by plane of nutrition. Estimates of heat production from these balance data were confirmed by direct measurements made on about half of the ewes.Estimates of the gross efficiency of utilization for foetal growth of the combined energy from maternal tissue and from ME intake, after allowing for maternal main–tenance, were similar for each litter size but were 0·14 and 0·11 on the low and high planes of feeding respectively. Consideration of these together with other published observations suggested that efficiency of utilization of ME in pregnancy increases linearly with the ME concentration of the diet and at concentrations below 10 MJ/kg dry matter is less than the efficiency of utilization of energy derived from maternal tissue loss.

Description: SUMMARYThe weights of 44 twin foetuses, 99 triplets and 44 quadruplets, varying in gestational age from 55 to 145 days, were studied in relation to age, sex, litter size, uterine position, placental structure and weight, and ovulation rate. Triplet and quadruplet foetuses were more variable in weight, within litters, than were twins. The difference increased with foetal age and was attributed to increased competition between foetuses which were located within the same horn of the uterus. The effect was largely associated with differences in placental development, i.e. numbers of cotyledons and weight, but those differences did not entirely account for the reduction in foetal weight with increasing litter size. Differences in placental development, arising from embryo mortality, also accounted for the reduction in foetal weight when ovulation rate exceeded litter size. In contrast, differences in foetal weight associated with the sex of the foetuses were only partly mediated by differences in cotyledon weight. Foetuses in the larger litters are thus not only lighter in weight but are more variable in weight, the increased variability being controlled by events in early pregnancy.