Effect of dose of equine chorionic gonadotrophin on the estrus responses of gilts and weaned sows and effect of the interval between equine chorionic gonadotrophin and luteinizing hormone injections on sow performance
G. Cassar, DVM, PhD, Diplomate ABPV; R. M. Friendship, DVM, MSc, Diplomate ABPV; L. J. Zak, PhD; D. Rogan, DVM, PhD; R. N. Kirkwood, DVM, PhD, Diplomate ECAR
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Objectives: To determine estrus and ovulation responses of gilts and sows to different doses of equine chorionic gonadotrophin (eCG), with different intervals between eCG and luteinizing hormone (pLH) injections.
Materials and methods: Experiment One: gilts received 0 (Control; n = 20), 600 (n = 42), or 900 (n = 42) IU eCG, then were exposed to a boar daily for estrus detection. Experiment Two: weaned primiparous sows received 600 (n = 56) or 900 (n = 59) IU eCG, 2.5 mg pLH 80 hours later, and a single insemination 36 hours after pLH. Controls (n = 43) received no hormones and were inseminated at estrus detection and 24 hours later. Experiment Three: weaned mixed-parity sows received 600 IU eCG at weaning and 2.5 mg pLH 72 (n = 107) or 80 hours (n = 116) later, or served as Controls (n = 66). Sows were inseminated as for Experiment Two.
Results: Experiment One: rate of ovulation was greater at the higher eCG dose (P < .05). Experiment Two: sows receiving 900 IU eCG had a higher farrowing rate than controls (P = .03), with sows receiving 600 IU eCG being intermediate. Litter sizes were unaffected. Experiment Three: farrowing rates were higher for the eCG treatment than for Controls (P < .05). Litter sizes were unaffected.
Implications: These data suggest that the dose of eCG should be 900 IU for induction of estrus in young females. For controlled ovulation, the eCG-pLH interval can be reduced to 72 hours without affecting reproduction.
Keywords: gonadotrophins, estrus, ovulation
Cite as: Cassar G, Friendship RM, Zak LJ, et al. Effect of dose of equine chorionic gonadotrophin on the estrus responses of gilts and weaned sows and effect of the interval between equine chorionic gonadotrophin and luteinizing hormone injections on sow performance. J Swine Health Prod 2010;18(4):182-186.
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