ABSTRACT
The response to the male effect was studied in two Saânen and two Alpine flocks over 5 consecutive years. Adult male and female goats were exposed to artificial long days (16h light and 8h darkness, 16L:8D) in open barns for approximately 3 months (between December 1 and April 15) followed by a natural photoperiod. Goats were treated for 11 days with fluorogestone acetate (FGA) or progesterone (CIDR) immediately before joining. Bucks carrying marking harnesses with adapted aprons joined females 49-63 days after the end of the long-day treatment (between April 30 and June 5) and were left with them for 5 days. In experiment 1 (n=142), FGA- and CIDR-treated goats were inseminated at a time based on the detection of oestrus. Two insemination groups were distinguished by the occurrence of marking over a 48-h period. Earlier (group 1) and later (group 2) buck-marked goats received one single insemination 12-24h or 0-12h after marking, respectively. Unmarked goats were inseminated along with group 2. In experiment 2 (n=344), FGA-treated goats were inseminated 52 and 70 h (52 h:70 h group) or 52 and 75 h (52 h:75 h group) after joining. In experiment 3 (n=285), FGA-treated goats were inseminated 52 h (1-AI group) or 52 and 75 h (2-AI group) after joining. In all experiments, an external control group given the "classical" insemination program was analysed. Over the 5-year period, 92% of the goats exhibited an LH surge during days 1-4 after joining and 98% of them ovulated. Eighty-seven percent of the LH surges detected in milk occurred during the 33-57 h interval after joining, indicating that ovulation took place around 45-69 h. In experiment 1, 96% of the goats were marked 22-70 h after joining. Kidding rate (KR; 78%) was similar between insemination groups and between FGA- and CIDR-treated goats (p>0.05). Most of the goats (95%) were inseminated during the interval between 15h before and up to 4h after ovulation. KR was not affected by the time between detection of marking and insemination or between insemination and ovulation (p>0.05). In experiment 2, KR (75%) was similar in both insemination groups (p>0.05). In experiment 3, KR was higher (p<0.05) in the 1-AI (71%) than the 2-AI group (57%). In all experiments, KR of the control group (68-73%) was similar to that achieved in goats induced to ovulate by the male effect. Prolificity (2.1+/-0.7) was not affected by any of the factors examined (p>0.05). In conclusion, high fertility can be achieved during anoestrus when 1 or 2 inseminations are performed over a 24h period, determined by oestrus or by the introduction of the buck, if light-treated goats receive 11-day FGA or CIDR treatment and are then induced to ovulate by the male effect.
