Abstract:
Single fixed-time AI is the breeding protocol inseminating the sows once with either fresh or frozen-thawed (FT) semen at fixed time after ovulation induction without estrus detection. To develop the success single fixed-time AI protocol in Thailand, factors affecting the efficacy of single fixed-time AI were evaluated. Additionally, we also evaluated the effect of using lecithin in cryopreservation extender on FT semen qualities in order to find the possibility to perform single fixed-time AI using sperm preserved in lecithin based extender. It was found that administration of 10 ug buserelin at 72 h after weaning decreased weaning-to-ovulation interval compared to spontaneous ovulation (127.6 vs. 157.2 h). However, the response of buserelin injection was also affected by season and weaned sows conditions. Hot season prolonged ovulation time. Weaned sows with lactation length (LL) ≥20 days, litter weight (LW) <67 kg, or body condition score (BCS) ≥3, or high backfat reserve after weaning had better buserelin responses. The single fixed-time AI using 10 ug buserelin injection at 72 h after weaning and insemination the sows at 32 h later was successfully performed under tropical climate with acceptable litter size compared to conventional AI (12.0 vs. 12.8 piglets per litter). A decreased litter size was also observed when single fixed-time AI was performed in the hot season or using intrauterine insemination (IUI) with a reduced number of sperm. Finally, the FT semen qualities of sperm preserved in cryopreservation extenders containing 20% egg yolk or 3% lecithin and 10% egg yolk were higher than those in 6% lecithin extender. In conclusion, the present study found that hot season decreased response of buserelin injection, delayed ovulation time and decreased sows reproductive performances after single fixed-time AI. Weaned sows with LL ≥20 days, LW <67 kg, BCS ≥3 or high backfat had better responses to buserelin injection. Single fixed-time AI using the IUI with a reduced number of sperm decreased litter size. Replacing of egg yolk with lecithin in cryopreservation extender did not increase FT semen qualities. The precise concentration of lecithin should be further investigated to perform single fixed-time AI using FT semen preserved in lecithin-based extender.
