Induced Breeding in Anestrous Milking Ewes of Dairy Breeds: Comparison of Norgestomet, Medroxyprogesterone and Fluorogestone in Two Regimes of PMSG

Induction of fertile estrus during seasonal anestrus in ewes and fall born ewe lambs

“…Greyling et al (1994) also observed no difference in the conception rate (Mean, 68%) and lambing rate (mean, 82%) in anestrous ewes treated with 30, 40 or 60 mg MAP impregnated sponges and 300 IU eCG at sponge withdrawal. Alifakiotis et al (1982) noted that the pregnancy rate of anestrous ewes treated with a 1.3 mg norgestomet implant (54%) was similar to that observed by Carpenter and Spitzer (1981), (51%) using a total of 4.5 mg norgestomet (1.5 mg at insertion and a 3 mg implant). However, the conception rate was consistently lower with a 3 than a 6 mg norgestomet implant in ewes synchronized during the breeding season (Woody et al, 1983).…”

“…The estrous response and pregnancy rate to the first service was comparable to responses observed in FGA-synchronized ewes (Spitzer and Carpenter, 1981). The effectiveness of norgestomet implants to induce estrus in anestrous ewes has been evaluated (Carpenter and Spitzer, 1981;Alifakiotis et al, 1982;Tritschler II et al, 1991). Carpenter and Spitzer (1981) reported that the estrous response and conception rate were 79 and 51 %, respectively in anestrous ewes following treatment with 3-mg implant for 10 days plus 1.5 mg norgestomet and 0.5 mg estradiol.…”

“…The use of intravaginal sponges impregnated with several different progestogens were later observed to be effective in blocking estrus and ovulation in cyclic ewes (Robinson et al, 1967a) and induction of estrus in anestrous ewes (Moore and Holst, 1967;Robinson and Moore, 1967;Robinson and Smith, 1967). Intravaginal pessaries were subsequently manufactured with FGA and MAP, and utilized for the induction of estrus in anestrous ewes (Alifakiotis et al, 1982) and the synchronization of estrus in cyclic ewes (Spitzer and Carpenter, 1981;Rhodes and Nathanielsz, 1988). Evans et al (1962) and Hogue et al (1962) (Hogue et al, 1962).…”

“…The estrous response, conception and pregnancy rates were 79, 40, 40%, respectively and were higher than that observed in control ewes after a 16 day breeding period. The estrous response, percentage of ewes lambing to the first service and overall was not different in anestrous ewes treated with norgestomet ear implants (1.3 mg), FGA (40 mg) or MAP (60 mg) sponges for 14 days (Alifakiotis et al, 1982). Welch et al (1984) first reported the use of controlled internal drug release dispensers (CIDRs) for synchronization of estrous in ewes.…”

“…Thereafter, the standard treatment for induction of estrus and ovulation involved progestogen pre-treatment with eCG at progestogen withdrawal (Gordon, 1963bcde;Robinson and Smith, 1967a;Gordon, 1971;Carpenter and Spitzer, 1981;Alifakiotis et al, 1982;Ainsworth and Downey, 1986;Hamra et al, 1986;Hamra et al, 1989;Tritschler II et al, 1991; Reviewed in Robinson, 1968;Gordon, 1977;Thimonier and Cognie, 1977;.…”