Hormonal therapy for sows weaned during fall and winter

Sows from five commercial herds were weaned in the fall and winter and used to ascertain the potential application of hormonal therapy to stimulate su bsequent litter size born. At weaning sows within parity (1, 2, and 3 throu gh 6) and lactation length classification (early weaned, less than or equal to 14 d; conventionally weaned, > 14 d) were randomly assigned to treatmen t. Treatments were injection with P.G. 600 (400 IU PMSG with 200 IU hCG) at weaning or no treatment. Sows were individually observed for estrus and ma ted following protocol for each herd. Breeding, culling, and farrowing data were collected. Treatment with P.G. 600 did not change subsequent rebreedi ng performance for sows at parity 1 or parities 3 through 6. However, conve ntionally weaned parity-2 sows treated with P.G. 600 were more likely (P < .05) to return to estrus than conventionally weaned controls (99.0 vs 93.6% , respectively). For parity-1 and parity-2 sows, treatment did not signific antly change the likelihood for farrow percentage. However, the likelihood to farrow a litter was greater (P < .05) among P.G. 600-treated sows at par ities 3 to 6 that were conventionally weaned (84.4 vs 71.3%, respectively). Subsequent litter birth weight for parity-1 sows treated with P.G. 600 was lower (P < .02) than for controls (15.6 vs 16.6 kg, respectively). Subsequ ent litter size at birth was not affected by treatment for parity-1 or pari ty-2 sows compared with controls. However, early-weaned sows at parities 3 through 6 treated with P.G, 600 had more (P < .06) total number born than c ontrols (12.4 vs 10.6, respectively). Treatment with P.G, 600 improved repr oductive function within specific parity and lactation length classificatio n for sows weaned in the fall and winter.