Ventilation of hay with oxygen increased oxygen consumption (P< 0·001) and carbon dioxide formation (P<0·01) of two steers, when compared with nitrogen-ventilated hay. Heat production was about 5% higher in the oxygen-hay period than in the nitrogen-hay period (P< 0·001). No difference in digestibility of nutrients was observed between these treatments.

Two trials were carried out to investigate the effects of increasing calorie: protein (C:P) ratios of high iso-nitrogenous diets on the performance characteristics, nutrient digestibility, carcass quality and organ weights of 67 growing pigs of the Yorkshire and Landrace breeds, reared in a tropical environment on concrete-floored pens from 9 to 56-8 kg live weight before slaughtering and grading. The dietary protein content was approximately 24 % of dry matter in all cases, and the C:P ratios ranged from 153 to 184 kcal digestible energy/g in both trials. Results showed no consistently significant differences in gain and feed intake due to increasing C:P ratio, but feed conversion ratios consistently improved with increasing C:P ratio. Digestible energy consumed per kg of body weight gained also increased with increasing C:P ratio. The nutrient digestion coefficients did not appear to be significantly affected by the C:P ratio. With respect to carcass quality measurements, there were nonsignificant differences in dressing percentage and average backfat measurements, but significant differences in percentage trimmed fat with increase in C:P ratio. The carcass length, loin eye area, and percentage lean cuts decreased as the C:P ratios increased, the last two showing significant differences only in the second trial. The organ weights showed no significant differences due to increases in C:P ratio.

Genetic influences on body weights, taken at three-monthly intervals from birth to two years, were measured in the progeny of Angus, Boran and Red Poll bulls mated to Ankole, Boran and local Zebu cows. At two years old, progeny of Angus and Red Poll sires were 9% heavier than progeny of Boran sires. Progeny of Boran dams were 15% heavier than progeny of Zebu dams and 8% heavier than progeny of Ankole dams at two years. Differential performance by progeny of Ankole dams in different years suggested that genetic × environment interaction might be of some importance, and indicated the necessity of testing breed types over several years. Low and variable heritability estimates of weight-for-age up to two years old, and significant hybrid vigour effects on weight, indicated that in this environment, exploitation of hybrid vigour could be of great importance. Repeatability estimates for calf pre-weaning weights averaged 0·42.

Heritabilities of birth, weaning, 6-month and yearling weights adjusted for significant non-genetic factors and obtained from half-sib correlations were 0·10±0·03, 0·22±0·05, 0·37±0·09 and 0·48±0·07 respectively. Genetic correlations of birth weight with later weights were small and negative except with weaning weight. Genetic correlations among other weights were large and positive. The phenotypic correlations among these weights were positive and statistically highly significant.

The voluntary intake of water by 24 groups of 3 to 6 Large White pigs (range of mean body weight: 21 to 73 kg) was measured during a total of 48 periods lasting 3 to 12 weeks each in a large calorimeter equipped as a pig pen. The calorimeter temperature was controlled between 7° and 33°C and the pigs were fed at levels ranging from 42 g feed/kg body weight per day to maximal intake. The mean water: feed ratios were between 2·1 and 2·7 at temperatures between 7° and 22°C, and between 2·8 and 5·0 at 30° and 33°C. The range of mean water consumption extended from 0·092 to 0·184 litre/kg body weight per day.

The least squares analysis on birth, weaning, 6-month and yearling weights in Magra lambs showed that years of lambing, age and weight of dam at lambing and sex of lamb significantly affected all the body weights except the age of dam which did not significantly affect 6-month and yearling weights. Adjustment of these weights for significant effect will be necessary in obtaining estimates of genetic and phenotypic parameters.

The female progeny of Angus, Boran and Red Poll bulls mated to Ankole, Boran and Zebu cows were compared. Heifers by Angus and Red Poll sires out of Boran and Zebu cows could be mated at an average age of 23 months with excellent calving percentages, whereas Boran-sired heifers and heifers from Ankole cows were not ready for service at this age. Lactation stress caused heifers suckling calves to lose 4% of body weight over a 7½ month suckling period, while heifers not suckling calves gained 14% in body weight. Heifers by Red Poll sires did not provide more milk for their calves, as measured by early growth rate, than heifers by Angus or Boran sires. The effect of hybrid vigour on mothering ability of F1 dams was at least as great as it was on the early growth of the F1 crossbreds themselves.

Growth from two years to three years and carcass yield and composition were evaluated in nine types of steers produced by mating Angus, Boran and Red Poll bulls to Ankole, Boran and local Zebu cows. One hundred and nine steers were slaughtered at the average age of 3 years and 1 month.

At three years of age, steers by Angus and Red Poll sires were 7% heavier than steers by Boran sires, while progeny of Boran and Ankole dams were 14% heavier than progeny of Zebu dams. Significant hybrid vigour effects on weight-for-age were found.

After adjustment for weight and age at slaughter, linear carcass measurements supported the impression that steers by Angus sires were more compact and blocky than steers by Red Poll and Boran sires and that progeny of Ankole dams were longer in the leg and body than progeny of Boran and Zebu dams. Steers by Red Poll sires appeared to have a higher fat content than steers by Angus and Boran sires on the basis of dissection of a tenth rib sample joint. Progeny of Boran dams had a higher dressing percentage than progeny of Ankole and Zebu dams. Hybrid vigour appeared to have little effect on carcass traits.

Records of milking rate, milk yield and milk composition were collected over 12 yr from 123 Ayrshire heifers in their first lactation in one herd. Three direct measures of milking rate, i.e. peak flow rate, machine rate and overall rate were closely correlated and each was also correlated with total lactation yield of milk. Milking rate accounted for only a very small part of the variation in fat and total solids percentages. The mean yield of milk per milking in early lactation was a better predictor of total lactation yield than was milking rate but, among animals giving the same early lactation yield of milk, the faster milkers gave higher lactation yields than the slower milkers.

From among a group of ewes in which oestrus had been induced following progesterone and PMS treatment and which had been mated in the spring, those lambing in early October were used for this experiment. They were divided into three treatment groups: (1) reared their lambs for 24 hr, (2) reared lambs for 16 days and (3) reared lambs for 75 days.

For the ewes rearing single lambs only in groups 1, 2 and 3, 100% (8 of 8), 93% (13 of 14) and 65% (11 of 17) respectively exhibited oestrus between lambing time in autumn and early winter (P<0·05). The average interval to post-partum oestrus was 29, 37, 50 days for group 1, 2 and 3 respectively. Group 3 exhibited first oestrus later than group 1 (P<0·01). These data show that lactation even during the peak of sexual activity has some suppressing effect on both the percentage of ewes showing oestrus and on delaying the onset of oestrus exhibition.

Regression equations predicting weight and percentage of both forequarter and total side retail cuts from 126 beef carcasses were calculated. Dissectable shank muscle weight, shank bone weight and shank soft tissue weight, but not shank fat weight, were useful in predicting weight of forequarter and total retail cuts. However, intact shank weight was as valuable as any single dissection component of the shank in predicting weight of both forequarter and total retail cuts. Separable muscle, fat, bone and soft tissue percentages of the shank were not useful in predicting percentage retail cuts of either the forequarter or the entire right side.

Hybrid vigour effects were measured on weights at birth and at 3, 6, 9 and 12 months, in crosses between Red Poll and Boran cattle. Means of crossbred weights were superior to means of purebred weights by 9·7% at birth and by 26·4% to 29·7% at 3–12 months. Boran cows had superior mothering ability to Red Poll cows, judged by the early growth of reciprocal cross calves, and lost less body weight over a nine-month lactation period.

Attempts were made to improve the nutritive value of diets based on separated milk and barley by adding free lysine and methionine. Feeding trial and nitrogen metabolism studies showed small beneficial responses to lysine, but not to methionine; the effects however were not statistically significant.

Dried poultry manure, produced locally by sterilization and drying, was evaluated as an addition to a conventional diet, at levels of 10, 20 and 30%, for growing pigs from 23 to 85 kg live weight. The 32 pigs remained healthy and the dried manure had no apparent adverse effect on the carcasses.

There were significant linear relationships between the amount of manure added to the conventional diet and growth rate, feed conversion efficiency and certain carcass characteristics. For every 10% addition of manure, growth was reduced by 0·02 kg/day, feed conversion efficiency by 0·25 units and killing-out percentage by 0·96. The dried manure contained about 30% crude protein and was a rich source of minerals.

Two groups of five lambs were removed from their dams within 48 hr of birth and artificially reared to a slaughter weight of approximately 32 kg on a milk replacer given cold, hay and concentrates. Voluntary intake of the feeds was recorded together with growth rates and carcass composition of the lambs.

The two groups of lambs were slaughtered at 58 or 67 days of age with growth rates of 459 and 433 g/day, respectively. The mean milk replacer dry matter consumed per lamb was 34·9 kg and 39·3 kg and concentrate dry matter intakes were 3·1 kg and 4·1 kg. Intakes of hay were negligible. Food conversion efficiencies were 0·70 and 0·67 kg of live-weight gain per kg of dry matter consumed. The mean carcass weights were 18·1 kg and 19·5 kg with mean muscle, bone and fat contents of 48·7%, 16·2% and 35·1 % for lambs slaughtered at 58 days and 48·0%, 14·7% and 37·2% for those slaughtered at 67 days.

The deposition of body and subcutaneous fat was compared in two groups of fat-tailed sheep, the one group docked shortly after birth and the tails of the other left intact. The slightly heavier live and carcass weights of the latter animals could be accounted for almost entirely by their significantly heavier weights of caudal fat, there being no firm evidence in support of increased internal or subcutaneous fatty deposition following amputation of the cauda.