title: Regulation of the estrous cycle in ewes with progestin containing implants: Influence of dose and day of cycle at treatment.
abstract: 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.
authors.affiliation: Department of Animal Industries University of Connecticut Storrs, Connecticut 06268 USA.
authors.forename: C O
authors.initials: CO
authors.lastname: Woody
authors.forename: S L
authors.initials: SL
authors.lastname: Beauchene
authors.forename: R C
authors.initials: RC
authors.lastname: Feccia
authors.forename: P A
authors.initials: PA
authors.lastname: Sepe
authors.forename: F M
authors.initials: FM
authors.lastname: Higgins
authors.forename: W A
authors.initials: WA
authors.lastname: Cowan
authors.forename: J W
authors.initials: JW
authors.lastname: Riesen