Induced breeding in anestrous milking ewes of dairy breeds: Comparison of norgestomet, medroxyprogesterone and fluorogestone in two regimes of PMSG

• Published in: Theriogenology Vol. 17; no. 6; pp. 603 - 610
• Main Authors: Alifakiotis, T., Michailidis, I., Gavrilidis, G.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1982
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/0093-691X(82)90058-9

The present investigation compares the suitability of norgestomet versus medroxyprogesterone and fluorogestone in inducing breeding in anestrous lactating ewes. Six hundred lactating ewes of two local dairy breeds were randomly divided into three equal groups during the spring. Ewes in group I were treated with 60 mg of medroxyprogesterone and in group II with 40 mg of fluorogestone using impregnated polyurethane vaginal sponges for 14 days. Ewes in group III were treated with 1.3 mg of norgestomet in impregnated mini-implants, placed subcutaneously in dorsal pinnae of the ear. The day the sponges and implants were removed, the ewes in each group were randomly allocated in two subgroups, a and b, and received 500 I.U. and 1,000 I.U. of PMSG, respectively. Vasectomized rams were used for estrus detection and fertile rams for hand mating. The percentage of estrus exhibition and subsequent mating was similar among groups (98 and 84%, subgroups Ia and Ib vs 100 and 100%, subgroups IIa and IIb vs 100 and 96%, subgroups IIIa and IIIb). The meantime of estrus exhibition ranged between 40.1h ± 6.2h to 42.3h ± 4.1h in IIIa and IIIb, 46.4h ± 6.1h to 49.2h ± 3.9h in Ia and Ib, and 48.3h ± 6.1h to 50h ± 4.6h in IIa and IIb, respectively. The lambing percentage ranged between 59 to 49% in IIIa and IIIb, 62 to 39% in Ia and Ib, and 71 to 28% in IIa and IIb, respectively. The percentage of subsequent estrus returns was ranged between 39 to 50% in IIIa and IIIb, 38 to 59% in Ia and Ib, and 26 to 70% in IIa and IIb, respectively. The lambing percentage of the returns ranged in the same level (86 to 100% in group I vs 92 to 96% in group II vs 91 to 90% in group III, respectively) as well as the prolificacy (178 to 209 in group I vs 187 to 176 in group II vs 200 to 188 in group III, respectively). It was concluded that induction of breeding in anestrous lactating ewes of dairy breeds, using implants containing only 1.3 mg norgestomet, might be a useful tool to improve efficiency of sheep production.