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 12–24 h or 0–12 h 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 15 h before and up to 4 h 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 24 h 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.