In the first of two trials, groups of 10 Chios lambs were fed on long or chopped straw for 13 weeks. They ate 0·61 and 0·65 kg per day, and lost a total of 7·6 and 8·5 kg body weight, respectively. Over the next 20 weeks, the supplementation of chopped straw with either 150 g of soya bean meal or a molasses-urea mixture given ad libitum increased straw intake. The decline in body weight was reversed and the lambs gained 0·04 kg/day on both treatments.

In Trial 2, the intakes of straw by non-lactating ewes were 0·78, 0·78 and 0·70 kg/day with supplements of molasses-urea, barley-urea and barley only, respectively. Ewes on the barley and the barley-urea supplements gained 5·3 and 4·6 kg respectively over the 16-week period whereas those given the molasses-urea supplement lost 2·6 kg.

In trials with 64 pigs growing from 37 to 60 kg or from 65 to 88 kg growth rate and food conversion were not affected by either a 10°C or a 20°C range in diurnal air temperature cycle compared with a constant temperature equal to the mean of the cycle when the mean temperatures were optimal. However, with a constant temperature and cycle mean at 6°C above optimum, performance declined with a 20°C range cycle.

The repeatability of ultrasonic backfat readings under field conditions was measured in a sample of 57 adult male (boars) and 77 young adult female (gilts) pigs. Repeatabilities of individual fat depths 6·5 cm off the mid-line at the shoulder, mid-back and loin ranged from 0·74 to 0·90. The repeatability of average backfat thickness was 0·92.

One hundred and twenty-eight Landrace and Large White pigs were allocated on the basis of sex, litter origin and initial weight to one of 16 treatments made up of four basal 16, 18, 20 and 22% protein diets, each supplemented with either 0·00,0·05,0·10 or 0·15% synthetic L-lysine; methionine was added to meet the levels earlier found to be optimal. All diets had a common energy level of 3740 kcal/kg DE and pigs were fed from 8 to 50 kg live weight.

Growth rate and feed efficiency improved as the protein levels were increased from 16 up to 20%. Only the 16 and 18% protein diets showed significant responses to additional lysine. Best overall gains and efficiency of gain was achieved on the diet with 20% protein and total dietary lysine and methionine+cystine levels of 1·17 and 0·66% respectively. Carcass leanness increased and fatness decreased as protein and lysine levels were increased, being best at the highest level (1·41%) of lysine studied.

Nitrogen retention indicated slightly lower protein and lysine requirement, efficiency of utilization being best on the 18% protein diet with added 0·15% lysine, giving a total dietary lysine level of 1·1% at the equalized methionine and cystine level of 0·66%.

It is indicated that diets providing between 18 and 20% protein in the diet, provided proper amino acid balance is maintained, would be optimal for pigs between 8 and 50 kg live weight.

1. An experiment involving 64 individually-penned pigs (32 females (gilts) and 32 castrated males (barrows)) was conducted over the live weight range 50 to 83 kg, to study the effects of a parenterally administered anabolic steroid upon the performance and carcass measurements of gilts and barrows given either a 15·0% or an 18·8% crude protein (CP) diet at two different levels.

2. The steroid significantly improved both daily weight gain (+5·2%) and food conversion ratio (+4·8%) of gilts and barrows.

3. There were no significant treatment interactions for either daily weight gain or food conversion ratio, but the data suggest that gilts responded to the hormone to a greater extent than barrows at the particular dose level of the steroid administered.

4. The steroid significantly improved the carcass, as assessed by linear backfat measurements, of pigs given the higher CP diet but had no effect upon carcass measurements of pigs given the lower CP diet.

Three experiments are described in which castrated male (steer) calves previously reared to 6 to 7 months of age on dried grass ad libitum gained weight faster, following turnout to pasture, than calves previously reared on a cereal/protein concentrate ad libitum. Rate of gain at pasture was found to be more an effect of previous rate of gain than of diet per se. There were indications that calves whose growth rate had been previously restricted ate more herbage per unit live weight than calves whose growthrate had not been restricted.

Female pigs (sows) which had lactated for about 10 days were allocated at random either to a control group or to a group given 75 mg methallibure per day for 5 consecutive days, followed by an intramuscular injection of 1000 IU PMSG. All sows were mated as soon as they came into oestrus and again 24 hr later. Nineteen out of 21 treated sows exhibited a controlled oestrus 9·4 + 0·25 days after weaning, compared with 21 out of 23 control sows in 8·2 + 0·64 days. Fourteen treated and 17 control sows conceived at that oestrus resulting in total pigs born per litter of 9·4 and 9·9 respectively. None of these differences was statistically significant.

An experiment was undertaken to examine the effects of the micronization process followed by grinding on the chemical composition of barley and on digestibility and nitrogen (N) retention in the growing pig. Micronization relative to normal grinding increased the dry matter (DM) content and starch availability in vitro and decreased the protein content of the cereal. Retention of N was not affected by the process but apparent digestibility of the DM, N and gross energy was improved. The improvement in digestible energy content of micronized barley over the ground grain was 3·8%. In a subsequent trial 24 pigs were individually and scale-fed a diet containing 75% of barley in ground or micronized and ground form over the liveweight range 33 to 80 kg. Processing treatment did not influence growth rate, DM food conversion ratio, killing-out percentage, deposition of backfat or area of ‘eye muscle’ in cross-section.

Twenty-four cows were used in a randomized block, continuous feeding trial to examine the effects of including 0, 25 or 50% of dried grass in a concentrate given to cows receiving grass silage ad libitum. The concentrates also contained barley, and soya bean meal to maintain the crude protein content at 16%, and were given at the rate of 0·4 kg/kg of milk. The treatments were imposed for a 6-week period after a preliminary feeding period of 4 weeks. At the beginning of the experiment the cows had, on average, calved 39 days previously. The mean intakes of silage dry matter were 7·60, 8·28 and 8·39 kg/day with the concentrates containing 0, 25 and 50% dried grass, respectively, and were significantly greater when dried grass was included in the concentrate. The mean milk yields of 200, 18·2 and 19·6 kg/day for the three treatments respectively were not significantly different. Body-weight change and milk composition were not significantly different between treatments.

The inclusion of 60 p.p.m. of 2,4-dichlorophenoxy acetic acid (2,4-D) or of M15† in the diet of lambs had no effect on the concentrations of volatile fatty acids and ammonia in rumen liquor, on the contents of haemoglobin, protein and non-protein nitrogen in blood or on the composition of the blood serum proteins. Over weeks 1 to 6 of experiment, there was a significant increase in live-weight gain in lambs receiving a diet containing M1S but the effect had disappeared at the end of 12 weeks. Inclusion of 2,4-D in the diet had no effect on live-weight gain.

1. In two experiments the nutritive value for the growing pig of wheat which had been micronized at temperatures of 155°, 190° or 220°C, flaked (rolled) and then ground was compared with wheat which had either been ground, or rolled and then ground.

2. In the first experiment 60 pigs offered individually, restricted amounts of feed were used in a growth and efficiency of conversion study. In the second experiment 15 pigs were used in digestibility and nitrogen retention studies.

3. The highest micronization temperature gave a significant depression in growth rate and in efficiency of conversion of dietary dry matter as compared with the other treatments for which there were no significant differences.

Two-way selection for muscle fibre diameter in mice was practised for four generations. The response was small and did not differ significantly from zero.