In a study involving 32 boars and 32 gilts penned in either single-sex or mixed-sex groups of eight over the live-weight range 20 to 80 kg, the system of penning did not influence performance or carcass measurements, and with boars had only slight effects on the colour and ultimate pH of the m. longissimus. Sensory panel evaluation of heated backfat from fresh and cured carcasses of boars showed a similar and low sex odour level for single- and mixed-sex groups. System of penning did not influence the extent and duration of agonistic behaviour nor the incidence of mountings.

An operant conditioning technique was used to determine whether the reinforcement value of grains and seeds preferred by sheep could be increased by crushing the food. Five sheep were trained to press a plate to receive a food reward. The rate of pressing on a progressive fixed ratio schedule of reinforcement was used as a measure of reinforcement value. Five foods were tested: barley, wheat, oats, lupins and peas. Crushing the foods had no effect on rate of pressing, whereas there was a great deal of variation between sheep and between foods. The preferred foods were wheat and barley.

The hypothesis is proposed that pigs will induce a mechanical stress, by huddling and over-lying, that is related to the degree of thermal stress experienced. Measurements of the floor area covered by groups of 12 pigs have been used to validate the hypothesis.

Two hundred and twenty-four pig carcasses were used to compare the Hennessy Grading Probe and the Fat-O-Meater in their accuracy for measuring fat and muscle thickness (m. longissimus). Accuracy was defined in terms of precision and bias. The precision (relationship between repeated measurements) of the two probes in measuring fat and muscle thickness varied with the probing locations. When differences were detected, the higher precision was found with the Fat-O-Meater. The mean bias in measuring fat thickness was negative for the Hennessy Grading Probe (P < 0·01); however, for the Fat-O-Meater, no mean bias was detected. Furthermore, the extent and the direction of the bias in measuring fat over the range of fat thickness studied varied with the probe and the probing location.

Fifty-three 7-day nitrogen balances were made using 13 control (C) and 15 selection line (S) Large White boars. Six feeding treatments were imposed, ranging from a Jevel estimated to maintain weight to a level aimed at inducing a fast growth rate from giving food twice daily to appetite for 30 min. Nitrogen retention did not differ significantly, but C boars retained slightly more than S boars at the lowest food intake, while S boars retained Slightly more than C boars at higher food intakes. The slopes of the regression of nitrogen retention against food intake for growth was steeper for S than for C boars (P > 0·05). It is concluded that great care should be taken in using metabolism experiment results to predict changes in body composition.

Forty entire male pigs, between 63 and 147 days of age, and weighing initially 21 kg, were given a basal diet containing 1·8 g methionine per kg, and based on wheat, sorghum and lupin-seed meal (Lupinus augustifolius cultivar Unicrop), supplemented with 0, 0·2, 0·4 or 0·6 g methionine per kg.

Supplementing each kg of the basal diet with 0·2 g methionine per kg significantly increased growth rate by 105 g/day and improved efficiency of food conversion between 21 and 35 kg live weight. Increasing the supplementation of methionine to 0·6 g methionine per kg diet increased growth rate between 21 and 35 kg live weight by a further 26 g/day but did not affect efficiency of food conversion. Between 35 and 71 kg live weight, performance was not improved by supplementation of the basal diet with methionine.