Three experiments were carried out in which the level of feed intake of pigs growing from approximately 30 to 90 kg was alternately raised and lowered, using different amplitudes and time-periods. Within each experiment, the total feed intake and the length of the experimental period were the same for all treatment-groups.

The two amplitudes which were examined were 112%–88% and 125 %–75% of standard scales of feeding. The time-periods between switches to the alternate level were 1, 3, 7 or 14 days. The impact of the fluctuations in feed intake on overall performance and carcass composition was either trivial or small, and in no case exceeded 5% for any one measurement. It is concluded that fluctuations in feed intake occurring in practical situations will have only trivial effects on performance, provided that pigs receive similar amounts of feed in the same overall period of time.

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.

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.

Three levels of soya bean meal (0%, 25% and 50% of the intake of hay dry matter) combined with three levels of pelleted barley (0%, 50% and 100% of the intake of hay dry matter) in a factorial arrangement of treatments were offered to Welsh Mountain ewe lambs receiving hay ad libitum for 14 weeks.

When barley was not given, soya bean meal added at 25% of the hay intake increased hay voluntary intake from 287 g/day to 412 g/day but hay intake was depressed to 339 g/day by a further increase in the level of soya bean meal. When barley was given, soya bean meal did not affect hay intake. With one exception, an increase in barley reduced hay intake, with the result that there were no differences between treatments in the digestible energy intakes of lambs receiving barley at each level of soya bean meal. In general, it was found that an increase in the concentrate allowance (barley + soya bean) reduced hay intake, whereas an increase in the crude protein content of the concentrate increased hay intake. The relationship between live-weight change, metabolizable energy intake and live weight was examined by regression analysis. Although live weight and voluntary intake were unrelated at the start of the experiment, a positive relationship emerged as the experiment progressed.

Sixty-four young male Sudan desert lambs were group-fed for 87 days on four diets, all containing approximately 10% crude protein. The four diets contained 0, 1·3, 1·7 and 2·7% urea, respectively.

Average daily gains were 0·15, 0·14, 0·14 and 0·13 kg; feed conversion ratios (kg of feed required to produce 1 kg live-weight gain) were 7·26, 8·14, 8·92 and 7·92; dressing percentages were 43·6, 42·1, 44·1 and 42·3.

Digestibility trials with lambs fed on diets with 0 or 2·7% urea gave higher digestibility coefficients for crude fibre and nitrogen-free extract for the urea-supplemented lambs. Crude protein digestibility and nitrogen retention values were lower for urea-supplemented lambs.

The discounted cash flow procedure of management accounting is used to evaluate national breeding programmes. Alternative methods of improvement of meat production from cattle born in the dairy herd are taken as examples. These schemes utilize selection for beef characters either in the dairy breed itself or within a beef breed, maintained in a small herd and used as a source of bulls for crossing by AI. In each case young bulls are selected for growth rate in a performance test, which precedes the progeny test for milk production in the dairy breed.

Greater rates of genetic progress and monetary returns are predicted from improvement of the beef breed, but both schemes are expected to yield a return on investment of over 15%. The net returns from the programme in the beef breed are influenced less by changes in assumptions.

Approximate, but simple, methods of computing the discounted returns are described.

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.

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.

In Merino rams studied over three seasons in New South Wales scrotal cover was correlated with face cover (0·29) and cover on points (0·16). Scrotal length was positively correlated with scrotal wool cover (0·17) and cover on points (0·28).

1. Effects of late pregnancy and early lactation on the voluntary intake of dried grass (Expt 1) and a poor quality seeds hay (Expt 2) by dairy cows are described. Each cow received a constant daily allocation of concentrates throughout late pregnancy. After calving half the cows received an 80% increase in concentrates, and the remainder continued to receive their pre-partum allowance.

2. Mean daily intakes of dried grass were higher than those of poor quality seeds hay. Intake of dried grass in week 2 of lactation was significantly correlated with the live weight of the cows, but a non-significant correlation was observed when seeds hay was offered.

3. During late pregnancy mean daily intakes of both roughages were approximately constant until the week immediately before par turition, when a significant decline occurred.

4. After calving mean daily intakes of both roughages increased throughout the first six weeks of lactation by 20–30% of the intake at week 1 post partum.

5. The 80% increase in daily concentrate allocation in early lactation caused a significant decline of 0·55 kg dried grass dry-matter intake per kg concentrate dry matter; the decline of 0·17 kg poor quality hay dry matter per kg concentrate dry matter was not significant.

1. British Friesian male calves were offered reconstituted milk substitute four times a day in steadily increasing quantities, so that the amount offered exceeded appetite after 14 days. They were given one of three dried herbage diets (pellets P1 and P2, and untreated material H2 made from the same crop as P2) to appetite, either from the start of the experiment (Treatment A) or from the start of weaning (Treatment W) 21 days after arrival. The experiment was terminated six weeks after the calves were weaned.

2. Grinding and pelleting (P2 v. H2) markedly reduced the in vivo digestibility of the diet, and the time of retention in the alimentary tract, increased the voluntary dry-matter intake by 50% and live-weight gain of the calves by 100%. The intakes of the two pelleted diets were similar.

3. The intake of diet H2 after weaning was greater in calves which had experience of the diet before weaning than in those which did not, but the intake of the pelleted diets was not affected by previous experience of solid food. The time required to eat unit weight of dry matter was four times as long for diet H2 as for the pelleted diets, and there were similar differences between diets in ruminating time. It is suggested that the development of solid food intake is influenced by the ease with which the diet can be eaten.

4. The initial increase in solid food intake after weaning was related to an increase in the times spent eating and ruminating, but later increases in food intake were achieved with no further increases in eating or ruminating time.

1. Two experiments have been performed to compare the performance of pigs given cool ‘whey’ (15°C) with that of pigs fed warm ‘whey’ (40°C). Pigs were penned individually and the ‘whey’ was reconstituted from concentrated materials.

2. In both experiments pigs offered cool ‘whey’ grew at a slower rate and required more dry matter/kg live-weight gain than pigs offered warm ‘whey’; the differences in rate of gain were 11 % at 16°C air temperature in Experiment 1 and 5% at 22°C air temperature in Experiment 2.

3. It was estimated that the ‘heat of warming’ for the cool ‘whey’ might have accounted for its entire effect on rate of gain.

Data were obtained from 27 pure Shorthorn, 22 Angus × Shorthorn, 31 Charolais × Shorthorn and 27 Hereford × Shorthorn cows, during 10 years. Angus × Shorthorn cows required the least number of services per conception (1·17), had the shortest average gestation lengths (280·6 days), and had a calving percentage of 88·2% and birth weight of calf of 29·8 kg. The respective figures for Charolais × Shorthorn were 1·21 services, 281·6 days, 88·3% (the highest) and 32·9 kg (the heaviest), for Hereford × Shorthorn 1·23 services, 283·6 days, 84·4% and 31·6 kg, and for pure Shorthorn 1·20 services, 282·2 days, 82·7% and 29·6 kg. Average calf weight at birth increased with the advance in age of cow up to 5 years, then showed little change. Seventy-two per cent of the crossbred cows calved for the first time at 2 years old compared with 65% of the Shorthorns. On the other hand, Shorthorn cows had the highest twinning percentage (2·9%) and the lowest single calf mortality at birth (1·4%). The maximum body weights of Angus, Charolais, and Hereford crossbreds and Shorthorn cows were 576·8, 655·8, 6254 and 553·8 kg respectively at 7–8 years of age.

The effects of freeze-branding young beef animals using two coolants were investigated and an attempt was made to avoid hide damage.

1. Branding with irons cooled in liquid nitrogen gave good markings but resulted in severe hide damage.

2. CO2-branding caused much less hide damage but gave fewer legible brands.

3. Legible brands with both coolants always resulted in some marking of the hide.

4. Branding on the jaw provided a satisfactory means of identification without loss of hide value.

1. A growth trial was carried out using 24 British Friesian steers given diets containing (1) 100%, (2) 60%, (3) 40% and (4) 0% concentrates and chopped dried grass up to 100%.

2. Daily dry-matter intake was significantly lower for steers on Treatment 1 than for steers on the other three treatments.

3. Rate of live-weight gain declined from 1·18 to 0·88 kg/day and carcass gain from 625 to 430 g/day between steers on Treatments 1 and 4.

4. Killing-out percentage dropped from 55·3% (1) to 51·9% (4) and the 8th-10th rib from steers on Treatments 3 and 4 contained significantly more crude protein and less ether-extractable matter than ribs from steers on Treatments 1 and 2.

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.

1. Two experiments are described in which polyethylene glycol was used to estimate the volume of fluid in the rumen of calves weaned at an early age from milk substitute on to diets of dried grass.

2. The limitations of the technique in relation to studies on voluntary food intake are discussed.

3. Linear relationships were observed between the volume of rumen fluid and the consumption of solid food within each of three diets, as solid food intake increased after weaning.

4. In one experiment, the concentration of dry matter in the rumen contents increased by 50% over the first 3 weeks after weaning. There was no significant change with time after weaning in the pH or the digestive efficiency, measured in vitro, of samples of rumen contents.

5. The times spent eating and ruminating increased rapidly after weaning on both a long and a pelleted diet, but then remained relatively constant despite continued increases in solid food intake. Eating and ruminating times were much greater for the long than for the pelleted diet.

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.