Effect of buck stimulus on mature and pre-pubertal norgestomet-treated goats.

Two experiments were conducted to assess the effect of buck exposure to synchronize estrus in mature and pre-pubertal norgestomet-treated crossbred (criolloxdairy breeds) goats. In experiment 1, 100 mature goats (25 per group) under range conditions were either teased at 48 or 24h before Sincromate-B (SMB; 9 days treatment of 2mg norgestomet) implant withdrawal. A third group was exposed to bucks 1 day after SMB treatment and another group was only exposed to bucks (control). Does exposed to bucks 1 day after SMB treatment tended to have a lower percentage of estrus (70% compared to 80% and 92% in other groups) and lower pregnancy rate (57.9 compared to 78.3 and 82.6 in other groups). At 156 days post-joining a significant (P<0.05) difference in cumulative kidding percentage was found between does teased 48h before implant removal (88.9%) and does teased 24h before implant removal (56.3%). Teasing without norgestomet was completely effective at stimulating estrus activity. In experiment 2, pre-pubertal does (n=36; mean 16.6kg BW) treated with SMB+PMSG+teasing tended to have a higher estrus response than SMB+PMSG treated female goat kids (91.6% vs. 66.6%; P=0.13). The results of this study indicate that, during the transitional period, the male effect was as effective as the synchronizing treatments involving SMB in inducing estrus in goats with reduced seasonal inhibition of reproduction. Also, buck exposure potentiates the effect of PMSG to induce estrus in norgestomet primed pre-pubertal does.