Effects of GnRH and prostaglandin combined with a short progestin regimen on the synchrony of estrus and ovulation in ewes during the breeding season
Calhoun, Andy Kyle
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The lack of effective, consistent synchronization protocols for ewes is a barrier to the use of artificial insemination in sheep. This study compared the estrus and ovulation percentage and window of synchrony of estrus and ovulation for ewes synchronized with three experimental protocols. The industry’s current standard protocol using PG600, an 11 d CIDR and PGF2a was compared to two alternative protocols utilizing GnRH, a 7 d CIDR and PGF2a. Forty Suffolk ewes were divided into 5 groups and each group was placed on a different protocol. Blood sampling began 18 h following CIDR removal and samples were collected every 2 h for 19 consecutively collections. Mean serum concentrations of LH differed between groups (P<0.05) from 22-42 h following CIDR removal. The two protocols using the shorter 7 d progestin regimen and GnRH to control follicular dynamics resulted in higher estrus and ovulation rates and an acceptable window of synchrony.