Subcutaneous progestin implants versus intravaginal sponges for dairy goat estrus synchronization during the transitional period

Two sources of progestin (a subcutaneous implant and a vaginal sponge) combined with pregnant mare serum gonadotropin (PMSG) were compared to induce estrus in 105 lactating and 17 nulliparous dairy goat does during the season of transition from anestrus to estrus. When compared with the untreated control group, both progestins performed equally well in inducing behavioral estrus (P<0.005) and pregnancy (P<0.03). The fertility rate was similar for both treatment groups, and lactation status and breed did not affect the outcome (pregnancy). The subcutaneous implant site selected (the ventral surface of the tail) was satisfactory. Implants were preferred over sponges because a shorter treatment period is required, they are commercially available in the United States, and they are suitable for use in nulliparous does. Progestins and PMSG treatment were successful in increasing the number of winter kiddings, thereby increasing winter milk production in a commercial dairy.