Efficiency of estrous synchronization in tropical sheep by combining short-interval cloprostenol-based protocols and “male effect”

This study assessed the efficacy of a protocol combining short-interval cloprostenol-based protocols and “male effect” for estrous synchronization in hair sheep. In Experiment 1, 24 ewes were randomly assigned to three groups (n = 8) and treated with cloprostenol on Days 3, 5 and 7 after ovulation, respectively. Estradiol secretion during the follicular phase was similar among groups. Onset of estrus (P < 0.001) and the timing of maximum LH concentration (P < 0.01) were earlier in group D3 than in D5 and D7 groups. During the subsequent cycle, the number and size of corpora lutea were higher (P < 0.05) in ewes of the groups D3 (1.9 ± 0.3 and 115.1 ± 14.3 mm²) and D5 (1.8 ± 0.2 and 100.2 ± 11.2 mm²) than in group D7 (1.3 ± 0.2 and 75.6 ± 6.4 mm²) group. In Experiment 2, 24 ewes were treated with two cloprostenol injections (7 days apart). Twelve ewes were exposed to “male effect” previous to an isolation period (ME group), whereas the remaining ewes were controls without male exposure (CTR group). Male effect induced earlier preovulatory LH surge (P < 0.05) and ovulation (P < 0.001) than CTR group. In Experiment 3, the estrus was synchronized in 68 ewes. Nineteen of them (group FGA) were treated using intravaginal sponges impregnated with fluorogestone acetate for 12 days and inseminated at 55 h. Forty-nine females (group ME) were treated like ME group. Twenty-four (ME48 group) and 25 ewes (ME55 group) were inseminated at 48 and 55 h after treatment, respectively. The fertility rate was numerically higher in ME48 than ME55 and FGA groups (62.5, 44.0 and 47.4%, respectively). In conclusions, the combined use of short-interval cloprostenol treatment and “male effect” may be an adequate alternative for synchronizing estrus and applying artificial insemination in hair sheep throughout the entire year.