1. In two experiments, each using three groups of six littermate castrated male pigs per group, the effects on cereal composition, apparent digestibility and nitrogen retention of micronizing barley and maize were studied.

2. The process increased the dry matter (DM) content and in vitro starch availability and decreased the nitrogen content of both cereals. When maize was flaked (rolled) subsequent to the process the ether-extract content was markedly decreased.

3. Nitrogen retention was not affected by the process but apparent digestibility of the DM, nitrogen and gross energy was improved. These effects were most marked when the process was followed by flaking, the improvements in such cases in digestible energy content over the unprocessed grain being 4·3% (P>0·05) for barley and 6·6% (P<0·05) for maize.

4. Soaking the unprocessed and micronized and flaked cereals before feeding did not significantly affect the results.

1. In each of two 2 × 3 factorially designed experiments 72 pigs were individually- and scale-fed diets containing 86·5% of maize, wheat or barley in ground or micronized, flaked and ground (micronized) forms.

2. In both experiments, the first between 17 and 20 kg and the second between 22 and 90 kg live weight, pigs offered the micronized maize and barley diets grew significantly faster and converted the dry matter of their diets significantly more efficiently than did pigs offered the ground maize and barley diets. There were no significant differences between the micronized and ground wheat diets in the first experiment but in the second experiment the micronized diet gave significantly inferior results.

3. In pigs slaughtered at 90 kg live weight those fed all the micronizedbased diets had significantly higher killing-out percentages than those fed the diets based on the ground cereals. Other within-cereal significant differences were those of increased carcass length in pigs given micronized maize and increased fat deposition in pigs given micronized wheat.

1. The experiment was designed to investigate the effect of growth at a high ambient temperature, 33–35°C, on the protein and energy metabolism of pigs, compared with 25°C. The high temperature caused an increase in rectal temperature of 1·4° to 1·7°C. The animals were given two low levels of feeding while growing between 25 and 70 kg live weight; energy and nitrogen retention were measured periodically.

2. The apparent digestibilities of the dietary dry matter and energy were decreased and urinary nitrogen losses were increased at the high temperature. Heat production was increased at the high temperature, by between 2% and 10%, the effect becoming more pronounced during the course of the experiment. Retention of energy and nitrogen was reduced at the high temperature.

3. The net efficiency of utilization of metabolized energy above maintenance was between 63% and 67%, and was not significantly affected by live weight or temperature. The results suggested that maintenance requirement was increased at the high temperature.

4. Analyses of sample joints indicated that the high temperature caused an increase in fat percentage only at the higher level of feeding; this result agreed with fat and protein retention calculated from the balances.

Fibre number and fibre size were measured in the flexor digiti V brevis muscle and other muscles in pigs of different breeds. A large variation in fibre number (200%) was found among the breeds. However, the fibre number in the flexor digiti V brevis was closely correlated with fibre number of other muscles in the same animal. Fibre number and size measurements were also carried out on animals at different ages taken from a relatively pure breed of pig. Fibre size was found to increase to differing extents in different muscles, although the increase in the flexor digiti V brevis was almost the same as in the longissimus dorsi. Fibre number did not change during growth. On the basis of these findings it is suggested that the flexor digiti V brevis is a suitable indicator muscle for genetic experiments.

Multiple birth percentage and wool production were studied on 338 ewes (907 lambing and 873 shearing records) representing two purebreds, Oxford (O) and Suffolk (S), and four crossbreds, O × S, S × O, Cheviot (C) × O and C × S mated to purebred and crossbred rams during 9 years. Oxford ewes had 24–32% (P<0·01) fewer multiple births than ewes of the other groups, while little difference between S and the crossbreds was observed. The heterosis of the OS and SO groups was 14·6 ± 4·1%. Multiple births tended to increase 0·8% for each kg increase in body weight of the dam (r = 0·13). The repeatability estimate for multiple births was 0·24. Fleece weight was significantly affected by age and by breed group, with OS and SO crosses producing 17% more wool than their parental breeds. The repeatability of fleece weight was estimated at 0·52 ± 0·15. Fleece weight was significantly correlated with multiple birth percentage (0·09) and body weight (0·32).

Suffolk ewes averaged 9·5 kg heavier than O ewes throughout their reproductive life. The two reciprocal crosses were heavier than both parental breeds. Suffolk ewes reached their maximum body weight at 4 years of age while Oxfords continued to gain weight up to 6 years.

Pushing the testes of lambs 1 to 2 weeks old into the body cavity and applying a rubber ring to cause atrophy of the empty scrotum, did not prevent most testes growing in a subcutaneous position. A modified technique used in a second experiment, which caused ablation of the tunica vaginalis as well as the scrotum, impeded more effectively the descent and growth of the testicles.

In the two experiments growth rates of the induced cryptorchids were, respectively, 15·3% and 6·0% (non-significant) greater than those of castrated males, dressing percentages were about 2 units lower, and fat depth over the eye muscle of 13th rib chops was 2·6 compared with 2·9 mm (non-significant) and 1·9 compared with 4·1 mm. Chops from the cryptorchids had a visual appeal similar to those from castrated male and from female lambs; differences in flavour detected by taste panel had no significant effect on overall flavour acceptability.

Tenderness did not differ significantly between sex groups, but age and Warner-Bratzler shear values were significantly and positively correlated as were ultimate pH of the meat and age at slaughter. Cryptorchidism induced by the modified technique probably permits the production of heavier carcasses with lower fat cover than on castrated males and avoids practical disadvantages that may be encountered in raising entire male lambs.

Sixty Scottish Blackface ewes were used in a 2 × 2 factorial experiment in which two levels of metabolizable energy (ME) were given during the final 6 weeks of pregnancy. In two treatments 1600 and 2000 kcal M E were given daily over the total period while in the remaining treatments daily ME intakes were 1200 and 1600 kcal ME during the first 3 weeks of the feeding period and 2000 and 2400 kcal ME during the last 3 weeks. Digestible crude protein (DCP) intakes were constant at approximately 30 g per head daily in the constant energy treatments and 15 and 45 g per head daily in the first and second periods respectively for the low-high energy treatments.

Energy intake had no statistically significant effect on lamb birth weight nor on ewe net body-weight change (change from the start of the experimental feeding period to immediately post partum). Ewes on low-high energy intakes had a significantly lower net body-weight loss than did ewes on constant energy intakes. Pattern of feeding had no significant effect on lamb birth weights. Negative nitrogen balances were found during the first feeding period where the daily DCP intake was approximately 15 g per head.

An experiment was carried out in which a cereal supplement was given to beef cattle, either in suspension in water or as a dry supplement. There were no significant differences between treatments in live-weight gain, food intake or food conversion ratios. Although there was a tendency for the digestibility coefficients of all constituents to be lower on the diet containing the liquid supplement, the differences were not statistically significant. It is concluded that giving a supplement in suspension has no adverse effect on the utilization of the overall diet and could facilitate mechanization of the feeding operation.

Changes in tocopherol concentrations in the milk of Shorthorn cows, and blood of their calves associated with a change from a winter diet of hay to lush spring pasture were examined. During the winter feeding period the tocopherol levels in the colostrum (108 μg/100 ml) and milk (40 μg/100 ml) were low. A significant increase occurred in the milk tocopherol concentrations after the cows were turned out to spring pasture. Immediately before the animals were turned out to pasture the tocopherol levels were lower in calves with high serum levels of glutamic oxalacetic transaminase, indicative of muscular dystrophy. Plasma tocopherol levels in all calves increased throughout the grazing period, reaching a maximum average value of 919 μg tocopherol/100 ml after 63 days. Six Limousin × Shorthorn calves out of a total of 41 died with nutritional muscular dystrophy but no mortalities occurred among 26 purebred Shorthorn calves.

1. The experiment involved four pairs of Jersey cows in a double reversal trial with two treatments.

2. The control and acetate treatments involved iso-caloric concentrate mixtures together with hay. The concentrates and hay were given in constant ratio of 3 : 1 and total feed intake was regulated according to milk yield. Cows on the acetate treatment received a dilute solution of fatty acids (1·7 % w/w) and an all-cereal concentrate mixture; those on the control diet received water and a concentrate containing 10% groundnut meal. The dilute solution of fatty acids provided approximately 31 % of the total digestible crude protein intake as ammonia-N, and 208 g acetate and 34 g propionate per day.

3. The two treatments gave similar dry-matter intakes. The acetate treatment caused a slight and significant depression of milk yield but the fat content of the milk and fat-corrected milk yield were slightly increased by treatment, though not significantly so. The results have been discussed with reference to the end products of digestion in the rumen and role of ammonia-N as a substitute for protein-N.

An experiment was conducted with 50 male Friesian calves between 5 and 11 weeks of age. Milled wheat straw (0·95 cm screen) was included in a pelleted all-concentrate diet at concentrations of 0, 15, 30 or 45 %. The nitrogen content of the diets was maintained by the addition of urea. The diets were given alone or with a chaffed lucerne hay or wheat straw supplement ad libitum. All diets contained 2 % sodium bicarbonate.

The feed intake and weight gains of the calves were increased significantly by the inclusion of 15 % milled wheat straw, but were reduced by 30 or 45 % straw. The supplements of chaffed wheat straw or lucerne hay ad libitum did not influence the performance of the calves. The inclusion of wheat straw in the diets reduced their dry-matter digestibility but the digestibility of acid detergent fibre was maximal with 27 % straw. The digestibility of nitrogen was significantly increased by 15% straw but reduced by further increases in straw.

The inclusion of wheat straw in the diets did not influence the pH of the rumen contents or the concentration of total volatile fatty acids in the rumen. Increasing the level of straw in the diet caused a significant linear increase in the proportion of acetic acid and decreases in butyric, propionic and valeric acids.

Two growth trials were carried out with a total of 112 British Friesian steers to examine the effects of offering all-concentrate diets containing different concentrations of crude protein. In Experiment 1 the steers were offered a diet containing either 17·5 % (H), 14·5 % (M) or 11·5 % (L) crude protein in the dry matter from 100 to 250 kg live weight and changed to diet M, L or one containing 9·5% crude protein in the dry matter (VL) between 250 kg and slaughter, so that the protein content of the diet offered to each steer was lowered by between 2 % and 3 % at 250 kg. In Experiment 2 the diets used were H and M between 100 and 250 kg and M and L between 250 kg and slaughter. Some steers in Experiment 2 were offered the same diet (M) throughout the experiment. Steers offered diet L between 100 and 250 kg ate less feed than steers given diet H and grew at a slower rate than steers given either diet H or M. Those steers given diet VL between 250 and 350 kg grew more slowly than those given diet M or L. For most steers a considerable saving in supplementary protein could be achieved by adopting an ML sequence rather than an HM or MM sequence when formulating dietary supplements.