Day of Injection does not Affect the Response

of Weaned Sows to PG600

R.N. Kirkwood

Alberta Pork Research Centre; AAFRD, 905 O.S. Longman Building, 6909-116 Street, Edmonton, AB, Canada T6H 4P2

It is recognized that primiparous sows have longer and more variable wean-estrus intervals than do later parity sows and that this can negatively impact the ability to achieve breeding targets. A large field study recently confirmed the efficacy of PG600 administered at weaning to induce a rapid and synchronous post weaning estrus in primiparous sows. However, it has been suggested that the optimal time of PG600 injection is the day following weaning.

Two-hundred-fifteen NPD primiparous sows were assigned to receive PG600 either on the day of weaning (W0; n=70), the day following weaning (W1; n=72) or to receive no injection and serve as controls (C; n=73). Estrus detection involved direct boar contact for 15 min daily from 2-d after weaning. Sows were bred naturally at estrus and again 24-h later.

Injection of PG600 reduced (P<0.01) the wean-estrus interval (4.5±0.1, 4.9±0.1, 6.0±0.3, for W0, W1 and C, respectively) and increased (P<0.01) the percent of sows bred by 7-d after weaning (82.9, 87.5, 57.5, for W0,W1 and C, respectively). The responses were not affected by day of injection. There was no significant effect of treatment on farrowing rates or subsequent litter sizes.

Implication: We conclude from these data that the response to PG600 in primiparous weaned sows is not influenced by day of injection.