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

Two experiments were conducted to assess the effect of buck exposure to syn chronize estrus in mature and pre-pubertal norgestomet-treated crossbred (c riollo x dairy breeds) goats. In experiment 1, 100 mature goats (25 per gro up) under range conditions were either teased at 48 or 24 h before Sincroma te-B (SMB; 9 days treatment of 2 mg norgestomet) implant withdrawal. A thir d group was exposed to bucks 1 day after SMB treatment and another group wa s only exposed to bucks (control). Does exposed to bucks 1 day after SMB tr eatment tended to have a lower percentage of estrus (70% compared to 80% an d 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) di fference in cumulative kidding percentage was found between does teased 48 h before implant removal (88.9%) and does teased 24 h before implant remova l (56.3%). Teasing without norgestomet was completely effective at stimulat ing estrus activity. In experiment 2, pre-pubertal does (n = 36; mean 16.6 kg BW) treated with SMB + PMSG + teasing tended to have a higher estrus res ponse 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, t he male effect was as effective as the synchronizing treatments involving S MB in inducing estrus in goats with reduced seasonal inhibition of reproduc tion. Also, buck exposure potentiates the effect of PMSG to induce estrus i n norgestomet primed pre-pubertal does. (C) 2000 Elsevier Science B.V. All rights reserved.