A total of 96 gilts were used in two experiments to determine the effect of live weight and body composition at about 170 days of age on age of attainment of puberty, ovulation rate and subsequent reproductive efficiency.
In the first experiment 48 crossbred (Large White ♂ × Landrace ♀) gilts were randomly allocated at 21 days of age to each of six treatment groups which gave six different intakes of a protein-adequate diet. The food intakes were designed to achieve six live weights ranging from 59·6 to 118·0 kg at boar introduction at 170 days of age. Age at puberty declined linearly from 202 to 173 days with increasing live weight at boar introduction (P < 0·01). Ovulation rate at puberty was also positively affected by live weight at 170 days (P < 0·05).
In the second experiment, four littermates from each of 12 litters were randomly allocated at 28 days of age to four treatment groups. The groups were offered diets of varying protein adequacy at different feeding levels up to boar introduction at 165 days of age. The treatment groups comprised a factorial design with the factors being live weight (light, L or heavy, H) and fat level (lean, 1 or fat, f relative fat content). At boar introduction, mean live weights were 70·6, 71·5, 101·3 and 100·0 kg, and mean backfat depths were 11·3, 20·9, 21·7 and 27·0 mm for the LI, Lf, HI and Hf groups, respectively. Heavier gilts at boar introduction were younger (183 v. 199 days, P < 0·01) at puberty. Ovulation rate at puberty was also greater (11·0 v. 9·5, P < 0·05) in the heavier gilts. Gilts which were leaner at boar introduction also tended to attain puberty earlier (186 v. 195 days, P < 0·10) than fatter gilts.
In both experiments neither the subsequent reproductive efficiency of gilts after parturition nor the performance of their piglets was significantly affected by body weight or body composition at boar introduction.