Use of PG-600™ and OvuGel™ in summer weaned first parity sows
Modern swine production relies on sows returning to estrus within 7d post-weaning, and OvuGel™, a vaginally delivered triptorelin acetate, can lead to synchrony in time of ovulation for these sows and facilitate timed AI. Parity one sows, those weaning large litters and those lactating under high thermal load are less likely to return to estrus in a timely fashion and, therefore, might be expected to have an inferior response to Ovugel™. PG-600™ is used to treat anestrus sows, including parity one females lactating under thermal load. At weaning in August, 2013, 544 parity one sows were divided into two experimental groups, Control and PG-600™. Control sows (n=270) were treated with OvuGel™ per label instructions at 96h post-weaning and mated using post-cervical AI with 3x106 cells 22-24h later. PG-600™ sows (n= 274) were treated the same as Control sows except they were first given PG-600™ IM at weaning according to label instructions. Detection of estrus was performed daily for 8 weeks following weaning. A row by column Chi Square test was used to evaluate proportion of sows returning to estrus and proportion of irregular returns (< 18 or >24d). A higher percentage of Control sows returned to estrus after their first mating than PG-600™ (24.81% vs 12.04%, respectively; P<0.0001), but of those the percentage of irregular returns did not differ by treatment (35.82% vs 27.27%; P<0.3927). Given that sows weaned large litters (12.62±0.09 and 12.55±.09 for Control and PG-600™, respectively) during August, a large proportion of sows experiencing delayed post-weaning estrus was expected. If these sows responded to PG-600™ the wean-to-estrus interval would be shortened, and a higher proportion should have become pregnant to the timed AI, which they did. Sows not conceiving, however, would have been expected to exhibit different patterns of return to estrus, and they did not.
Keywords: OvuGel, PG-600, ovulation