A 5 ML Dose PG-600® is Detrimental to Ovarian Function and Pregnancy Rate in Ewes During the Breeding Season

PG-600® (Intervet/Merck Animal Health, Madison, NJ) is a single dose injectable product containing equine chorionic gonadotropin (80 IU/ml) and human chorionic gonadotropin (40 IU/ml), which is labeled for estrus induction in swine. This drug is also routinely used off-label for out-of-season estrus induction in sheep. However, at the most common dose administered to ewes (3-5 ml), PG-600® is likely to overstimulate the ovaries, resulting in reduced pregnancy rates. The aim of the current study was to determine if a lower dose of PG-600® would not reduce the pregnancy rate. We hypothesized that the pregnancy rates of ewes treated with a low dose of PG-600® during the breeding season would not be different from controls. Polypay ewes were treated with CIDR inserts (Eazi-Breed™ CIDR, Zoetis, Kalamazoo, MI) for 10 days ...