Milk production data were collected on 8- and 9-year-old Angus × Hereford or Hereford × Angus; Charolais × Angus or Hereford; Jersey × Angus or Hereford; and Simmental × Angus or Hereford cows at days 14, 28, 56, 84, 112, 140, 168 and 196 after parturition. During the study, cows were given diets differing in quantity of brome grass (Bromus inermis) haylage. Lactation curves were estimated by the empirical equation Y(n) = n/aekn. Differences were observed among the breed crosses in 25-week lactation yield and time of peak lactation.

Eighteen Large White gilts were allocated to one of three treatments so that there were six gilts on each treatment. The treatments were (1) daily exposure to a nasal spray of boar saliva reinforced with 16-androstene steroid pheromones, (2) daily exposure to a nasal spray of saline and a mature boar for 20 min, and (3) daily exposure to a nasal spray of saline only.

The experiment began when the gilts were between 158 and 165 days of age, and was terminated when they reached 240 to 247 days of age, the gilts were slaughtered soon afterwards.

The results indicate that if salivary pheromones operate in the overall effect of the male on puberty attainment in gilts, the effect is of minor significance. Exposure to a mature boar confirmed the phenomenon of the 'male-effect' on puberty attainment in gilts.

Eight groups of six Yorkshire gilts were either exposed (BE) or not exposed (NE) to a mature boar at 160 days of age. These groups of gilts were slaughtered at 160, 165, 170 and 180 days of age for examination of their reproductive tracts.

NE gilts remained pre-pubertal from 160 to 180 days, with uterine weights of 121·6 g and 148·0 g respectively. Boar exposure induced ovulation in three out of five gilts by day 170 and in five out of six gilts by day 180. Uterine weight increased in BE gilts from 121·6 g at 160 days to 343·6 g, 298·0 g and 535·6 g by days 165, 170 and 180 respectively. This was accompanied by an increase in the number of large ovarian follicles (≤ 6 mm in diameter) from 0 at 160 days to 9·0 at 165 and 4·2 at 170 days.

These results confirm the potent stimulatory effect of boar exposure on puberty in gilts and suggest the use of ovarian status and uterine weight at slaughter 10 days after stimulation as a reliable indicator of the response of the pre-pubertal gilt to environmental change.

One hundred and twenty-five boars were given diets containing five levels of methionine: 1·5, 1·7, 1·9, 2·1 and 2·3 g methionine per kg diet, from 21 to 49 days of age. The mean weight gain of the pigs given the diet containing 1·5 g methionine per kg was 71 g/day and this increased linearly to 346 g/day for the pigs given the diets containing 2·3 g methionine per kg.

From 49 to 97 days of age all pigs were given a commercial pig grower diet containing 160 g protein per kg. Live-weight gains over this period increased linearly from 477 to 689 g/day with increasing methionine content of the starter diets. There was no compensatory weight gain.