Estrus presentation and distribution in ewes treated with intravaginal sponges impregnated with medroxyprogesterone acetate (MAP) in combination with pregnant mare serum gonadotropin (PMSG)

Abstract

The objectives of this study were: 1) to determine estrus presentation and distribution following a conventional method of estrus synchronization (progestagen-PMSG treatment) in an ewe herd and 2) to analyze estrus presentation and distribution in adult ewes and ewe lambs. During spring a total of 300 cyclic Merino ewes, including 231 adult ewes and 69 ewe lambs were treated with intravaginal sponges impregnated with 60 mg medroxyprogesterone acetate (MAP). After 14 days sponges were removed and 375 IU pregnant mare serum gonadotropin (PMSG) were administered i.m. Estrus detection was performed with vasectomized rams. Ewes were inspected for the presence of marks at 4-hours intervals. Sponge losses, estrus synchronization and distribution were analyzed for adult ewes and ewe lambs. It was detected 1% (3/300) of sponge losses. Estrus synchronization rate was 92.93% (276/297) for the ewe herd, being 93.48% (215/230) for adults and 91.04% (61/67) for lambs (p>;0.10). Estrus onset was detected from 28 to 68 hours following treatment in both classes of females. The interval between sponge removal and estrus onset was 46.88 ± 11.78 hours for the ewe herd, being 46.99 ± 12.22 hours for adult ewes and 47.31 ± 10.94 hours for ewe lambs (p>;0.10). Statistical differences were found only for the intervals 34-38 (p<0.10) and 50-54 hours (p<0.05) between adult ewes and ewe lambs. It was concluded that the treatment used was effective for estrus synchronization in ewes.