Pre- and peri-pubertal feed intake: effects on age at puberty and potential litter size of replacement gilts

The effect of moderate restriction of pre- and peri-pubertal liveweight gain on puberty attainment and potential litter size was investigated. At 69 days of age, 48 Large White/Landrace crossbred gilts (28.3 +/- 0.3 kg), were fed to attain a liveweight of 70 kg (LIGHT) or 100 kg (HEAVY) at 161 days of age (n = 24 gilts/treatment). At 161 days of age, half the gilts in each group were fed to gain liveweight at 0.5 (LOW) or 1.0 (HIGH) kg/day until puberty (n = 12 gilts/treatment). From 175 days of age, gilts received 20 min/day of full, physical boar contact. Gilts were artificially inseminated at the pubertal oestrus, with reproductive tracts collected 22 +/- 0.1 days later, and the number of corpora lutea and viable embryos recorded. LIGHT-LOW gilts were older (P < 0.05) at puberty compared with LIGHT-HIGH, HEAVY-LOW and HEAVY-HIGH gilts; 207.7 +/- 3.50 versus 191.7 +/- 3.65, 193.1 +/- 3.50 and 192.5 +/- 3.65, respectively. Treatment (HIGH vs LOW) increased (P < 0.05) pubertal ovulation rate (15.2 +/- 0.43 vs 13.1 +/- 0.47), oestradiol at oestrus (13.4 +/- 1.87 vs 9.1 +/- 1.22 pg/mL) and progesterone 72 h post-oestrus (7.1 +/- 0.48 vs 4.6 +/- 0.50 ng/mL). Embryo number (10.8 +/- 0.46) and survival (77.0 +/- 3.21) were unaffected (P > 0.05) by treatment. To conclude, puberty was delayed by chronic, but not acute, dietary restriction. Although short-term, moderate increases in feed intake increased pubertal ovulation rates, embryo numbers and survival were unaffected.