FAILURE OF AN INDUCED OVULATION DURING LACTATION TO IMPROVE SOW OR LITTER PERFORMANCE

Abstract

To test the effects of elevated blood progesterone on sow and litter performance, sixty-four, mixed parity Yorkshire × Landrace sows were allocated to be induced to ovulate during lactation (n = 34) or to serve as controls (n = 30). Ovulation was induced by an intramuscular injection of 1000 IU PMSG at 10 d and 500 IU hCG at 13 d of lactation. During lactation, sows were fed ad libitum a diet formulated to provide 13.1 MJ DE kg−1 and 16% crude protein while their feed intakes were recorded weekly. Piglets were weaned at 28–31 d of age. Of the 34 sows administered gonadotrophins, 19(56%) ovulated as indicated by elevated serum progesterone concentrations measured on days 20 and 28 of lactation. There was no effect (P > 0.1) of ovulation during lactation on sow feed intake, weight loss or backfat loss (5.5 vs. 5.4 kg d−1; 20.3 vs. 15.4 kg and 2.3 vs. 1.7 mm for ovulating and control sows, respectively). Similarly, there was no effect (P > 0.1) of ovulation during lactation on piglet weight gain from 14 to 28 d of age (3.1 vs. 3.1 kg) or on piglet preweaning survival (91.0 vs. 94.5% for ovulating and control litters, respectively). Sows ovulating during lactation had longer weaning to estrus intervals (9.4 vs. 5.4 d; P < 0.01). It may be concluded that ovulation and an elevated serum progesterone concentration in the latter half of lactation will not influence sow or litter performance but may increase the interval between weaning and estrus. Key words: Sows, ovulation, lactation, appetite, reproduction