EFFECT OF FEED-INTAKE DURING LACTATION AND AFTER WEANING ON SOW REPRODUCTIVE-PERFORMANCE

To study the effects of feed intake during lactation and after weaning on reproductive performance, 89 second-parity Lacombe sows were allowed 6 kg feed d-1 (H) or were restricted to 3 kg feed d-1 (R) during lactation and during the weaning to estrus interval (WEI); this resulted in a 2 X 2 factorial design (groups HH, HR, RH and RR). To minimize the confounding effects of duration of WEI on sow performance, the experiment was terminated 10 d after weaning. The diet was formulated to provide 12.4 MJ ME kg-1 and 16 % crude protein. Restricted feeding during lactation resulted in a longer (P < 0.05) WEI (7.3 d vs. 5.9 d). WEI was not affected by feed intake after weaning. Fewer (P < 0.05) sows feed restricted during lactation exhibited estrus by 10 d from weaning (31.8 % vs. 88.9 %). Ovulation rate was not affected by lactation or postweaning feed intake. However, embryo survival at 25 d of gestation was influenced (P < 0.05) by feed intake during both periods. The highest embryo survival (85 %) was in HR sows, and the lowest (64 %) was in RR sows. Blood samples were taken from 12 sows from each of the four treatments by means of indwelling vena cava cannulae at 6-h intervals from weaning until 24 h after mating or 10 d after weaning, whichever came first. Plasma gonadotrophin concentrations were reduced (P < 0.05) by low feed intake during lactation but were unaffected by postweaning feed intake. Peak preovulatory LH surge concentrations were highest (9.5 ng mL-1) in HR sows and lowest (7.6 ng mL-1) in RR sows (P < 0.05). These data confirm the adverse effects of restricted feeding during lactation on the reproductive performance of sows and indicate that such effects may be mediated through changes in plasma LH concentrations. No significant effect of postweaning feed intake on any measured factor was observed.