ABILITY OF ANDROGENIZED GOAT WETHERS AND DOES TO INDUCE ESTRUS IN GOATS UNDER EXTENSIVE CONDITIONS DURING ANESTRUS AND BREEDING SEASONS

Two hundred and ten Criollo crossbred goats under extensive conditions were randomly allotted to treatments to measure effects of exposure t o intact bucks (male), androgenized wethers (W) or androgenized does ( female), during the breeding season (November), on estrus response. Ca strated bucks were androgenized by injecting 60 mg of testosterone pro pionate every 3 days for 20 days and every 4 days during the teasing p eriod. Does were given 300 mg of testosterone during 2 consecutive day s, additional 300 mg on Day 5 and 60 mg every 4 days. After 13 days of stimulus, induction of estrus did not vary among teasers (87.1, 94.3 and 84.0% for male, W and female, respectively) but time to onset of e strus was significantly shorter (P < 0.01) for goats exposed to male ( 4.6 +/- 0.40 days) compared with goats exposed to W (6.9 +/- 0.39 days ) and female (8.1 +/- 0.46 days). In another experiment conducted duri ng the non-breeding season (April) a total of 150 goats were divided i nto two groups and exposed either to male or W. After 37 days of teasi ng the proportion of does exhibiting behavioral estrus was half of tha t observed during the breeding season. There was no significant effect of teasers on estrus response (46.7 and 51.7% for male and W, respect ively) but the time to onset of estrus was shorter for d (27.3 +/- 0.6 6) compared with W (30.7 +/- 1.26). Results of a third experiment show ed that pregnancy rate (76.5% vs 24.7%) and prolificacy (1.61 +/- 0.04 vs 1.25 +/- 0.08) was affected (P < 0.01) by month of breeding (Janua ry vs April). Results demonstrate that androgenized wethers and testos terone-treated does can be used successfully to induce estrus during t he breeding season of goats, but that, under these conditions, only ha lf of the does respond to this teasing during the non-breeding season, which leads to poor reproductive performance when goats were exposed to bucks during the non-responsive anovulatory period.