Human chorionic gonadotropin at parturition fails to consistently induce ovulation in sows
Roy N. Kirkwood, DVM, PhD; Steven C. Henry, DVM; Lisa M. Tokach, DVM; George R. Foxcroft, PhD
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Objective: Two experiments were performed to examine 1) the efficacy of human chorionic gonadotropin (hCG) in inducing ovulation in sows shortly after farrowing, and 2) the effect of hCG treatment on sow reproductive performance (wean-to-estrous interval) after weaning.
Methods: For experiment one, 69 mixed-parity sows on two commercial units in Alberta received 1000 IU hCG at various intervals within 24 hours postfarrowing. Blood samples were obtained 7-10 days later to determine progesterone (P4) concentration as an indicator of ovulation. For experiment two, mixed-parity sows from a commercial unit in Kansas were assigned by parity to receive a vulval-mucosal injection of 1000 IU hCG (n=240), or no injection (control; n=152) within 24 hours after farrowing. Of the hCG-treated sows, 122 also received a vulval-mucosal injection of 250 µg cloprostenol (PGF) 14 days after farrowing. Pigs were weaned at 11 days of age and sows bred at their first observed estrus after weaning.
Results: For experiment one, no more than 41% of sows that received a hCG injection ovulated as indicated by plasma P4 concentrations of more than 4 ng per mL. For experiment two, hCG- and hCG+PGF-treated sows had longer (P<.001) farrow-to-estrous intervals. The distribution of these intervals was biphasic. However, subsequent litter sizes did not differ among treatment groups.
Implications: These results demonstrate that the ability to induce ovulation in farrowed sows with hCG is too unpredictable to be of commercial value.
Keywords: ovulation, human chorionic gonadotropin, cloprostenol
Cite as: Kirkwood RN, Henry SC, Tokach LM, et al. Human chorionic gonadotropin at parturition fails to consistently induce ovulation in sows. J Swine Health Prod 1999;7(2):69-71.
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