Evaluation of hormone-free protocols based on the "male effect" for artificial insemination in lactating goats during seasonal anoestrus

Remerciements : Plate-Forme Phénotypage Endocrinologie, INRA, UMR PRC, 37380 Nouzilly, Centre Val de Loire

Inglés. Goat oestrous and ovulatory response to the ‘male effect’ was characterised to determine the time range over which fertile ovulations occur after buck exposure. The results were used to explore the efficacy of different hormone-free artificial insemination (AI) protocols aimed at diminishing the number of inseminations needed to optimise fertility. Adult bucks and does were exposed to artificially long days during winter, then exposed to a natural photoperiod before buck exposure (Day 0). Most goats (>70%) ovulated twice, developing a short cycle followed by a normal cycle over 13 days after buck exposure. Among them, 21% were in oestrus at the short cycle and 94% at the normal cycle. This second ovulation occurred within 48 h of Day 6 and was the target for AI protocols. In protocol A (n=79), goats were inseminated 12h after oestrus detection from Day 5 to Day 9. Up to six AI times over four days were needed to inseminate goats in oestrus. Forty-nine percent of the inseminated goats kidded. In protocol B (n=145), oestrus detection started on Day 5. The earlier (group 1) and later (group 2) buck-marked goats received one single insemination at fixed times on Days 6.5 or 7 and 8, respectively; unmarked goats (group 3) were inseminated along with group 2. In protocol C (n=153), goats were inseminated twice on Days 6.5 or 7 and 8 without needing to detect oestrus. Goats induced to ovulate by hormonal treatment were used as the control (n=319). Fertility was lower in protocol B than C and control (47 vs. 58 vs. 65% kidding; p≤0.05), whereas this was higher in buck-marked goats than unmarked ones (64 vs. 33%; p≤0.05). In protocol B, fertility can increase (>60%) when only goats coming into oestrus are inseminated. The best kidding rate (∼70%) was achieved when does were inseminated within 24h of the LH surge. Protocols involving insemination on Day 7 instead of Day 6.5 led to more goats being inseminated during this favourable time.