Regulation of the estrous cycle in ewes with progestin containing implants: Influence of dose and day of cycle at treatment

• Published in: Theriogenology Vol. 19; no. 5; pp. 677 - 684
• Main Authors: Woody, C.O., Beauchene, S.L., Feccia, R.C., Sepe, P.A., Higgins, F.M., Cowan, W.A., Riesen, J.W.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.1983
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/0093-691X(83)90108-5

Implants containing Norgestomet (G. D. Searle and Co., Chicago) were inserted subcutaneously in ewes on selected days of the estrous cycle. When ewes were treated for 13 days with 2 or 3 mg Norgestomet, implantation 13 days post-estrus reduced the number of ewes in estrus within 5 days of implant removal and reduced the number of estrous ewes that lambed compared with ewes implanted 4 days post-estrus. When ewes were implanted with 3 or 6 mg Norgestomet 4 or 13 days post-estrus, no difference in estrus response was found. Conception rate was not influenced by day of treatment, but was higher in those ewes treated with 6 mg than ewes treated with 3 mg. Compared to no treatment, treatment with 3 or 6 mg Norgestomet reduced the number of uterine and oviducal sperm recovered 12 or 24 hr after insemination from ewes implanted for 12 days 2 or 12 days post-estrus. However, more sperm were recovered from ewes treated 2 days than 12 days post-estrus with the principal increase occurring in ewes treated with 6 mg of Norgestomet.