A. W. Boyne

The estimation of the nutritive value of feeds as energy sources for ruminants and the derivation of feeding systems

The results of 80 calorimetric experiments with sheep and cattle, mostly conducted in Scotland, were analysed using a generalization of the Mitscherlich equation R = B (l–exp(– pG ))–l, where R is daily energy retention and G daily gross energy intake, both scaled by dividing by the fasting metabolism. The relations between gross energy and metabolizable energy were also examined. Methods of fitting the Mitscherlich equation and the errors associated with it are presented. It is shown that the gross energy of the organic matter of feed can be estimated from proximate principles with an error of ±2·3% (coefficient of variation) and that provided different classes of feed are distinguished, the metabolizable energy of organic matter can be estimated from gross energy and crude fibre content with an error of ±6·9%. Parameters of the primary equation made with cattle agreed with those made with sheep and there was no evidence of non-proportionality of responses on substitution of feeds in mixtures. The efficiency of utilization of gross energy for maintenance and for body gain of energy was related to the metabolizability of gross energy and, in addition, to fibre or to protein content. Prediction equations are presented which describe these relationships. It is shown that the primary equation can be manipulated to express a number of biological concepts and that its two parameters B and p can be simply derived from estimates of the two efficiency terms for maintenance and production. The results are discussed in relation to the design of feeding systems for ruminant animals and to the derivation of optima in their feeding.

Studies of the skeleton of the sheep I. The effect of different levels of dietary calcium during pregnancy and lactation on individual bones

1. Three groups of mature ewes were fed during pregnancy and lactation on rations differing in their calcium content. The mean daily intakes of calcium were 1·4 g. (group A), 4·5 g. (group B), and 7·4 g. (group C). Blood samples were analysed monthly for calcium and inorganic phosphorus. The ewes were killed at approximately 100 days after parturition and the skeletons isolated. Individual bones, either whole or divided into definite fractions, were analysed. 2. The level of calcium intake was without effect on the number of lambs born, birth weight, or growth while milk fed. 3. Blood calcium was significantly lower in group A than in groups B and C, but blood inorganic phosphorus was unaltered. 4. The resorption of bone substance was greater in group A than in groups B and C. 5. The severity of resorption varied between bones, and in regions within certain bones. Resorption was most severe in the vertebrae and pelvis, and only slight in the metacarpal, the metatarsal and the shafts of other long bones. Resorption of intermediate magnitude was found for the remainder of the skeleton. 6. Resorption was accompanied by reductions in the percentages of ash in bones, but this effect was proportionately less than the ash weight reduction. 7. Radiological observations made on flesh-free bones at the end of the experiment gave a picture of resorption similar to that presented by the data for ash weights and percentages of ash, namely that resorption was much greater in group A than in groups B and C.

The early weaning of pigs. VIII. Copper sulphate as a growth stimulant

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.

Studies of the skeleton of the sheep VII. A further comparison of skeletal resorption during pregnancy and lactation in ewes fed diets differing in digestible crude-protein value

1. An experiment has been carried out to compare the results of feeding the B-group diets of Parts II and III of this series to ewes during pregnancy and lactation. 2. The ewes fed a diet containing maize in place of dried molassed sugar beet pulp again maintained better bodily and skeletal condition. 3. The basis for other experiments in this series is discussed.

Studies of the skeleton of the sheep VIII. Studies of the effects of protein and energy intake on productivity and skeletal mineralization in the pregnant and lactating ewe

1. Effects on productivity and skeletal mineralization of high as opposed to moderate levels of protein and, or, energy intake by the ewe during pregnancy and lactation in the presence of adequate calcium, phosphorus and vitamin D have been studied. 2. Two experiments were undertaken. One experiment used 4½-year-old Cheviot ewes and the other used 3½- and 4½-year-old Scottish Blackface ewes. Weight records, blood samples and in vivo and flesh-free radiographs were obtained, and bone ash determinations were carried out. 3. The results showed that contrary to indications from earlier experiments in this series superiority in ewe weight, lamb growth, and mineralization of the ewe skeleton did not necessarily result from raising the protein and, or, energy values of the feed above the ‘moderate’ level. 4. Discrepancies between the in vivo and flesh - free radiological assessments were noted for consideration.

Studies of the Skeleton of the Sheep: IX. A further study of the mineralization of the skeleton of breeding ewes on two Scottish hill farms

1. After synchronization of oestrus by treatment with progesterone before tupping small groups of ewes were slaughtered at approximately monthly intervals from 5 weeks post-conception to around 3 months post-weaning on two widely differing Scottish hill farms. A few barren ewes were also slaughtered. 2. Ash analysis of the 3rd, 4th and 5th cervical vertebrae of the breeding ewes indicated that there was a striking similarity between the flocks in the mean percentage ash values of these bones and also in the decline in these values which occurred between early gestation and 12 weeks after lambing.