Gilt reproductive performance in a tropical environment after oestrus synchronization and fixed-time artificial insemination

Abstract

The present study was performed to evaluate the reproductive performance of gilts inseminated using fixed-time artificial insemination (FTAI) protocol. A total of 408 Landrace × Yorkshire crossbred gilts were included in the experiment. Gilts at 8 months of age were randomly allocated into three groups: control AI (n = 192), treatment 1–TAI (n = 117) and treatment 2–FTAI (n = 99). Gilts in the control AI group were inseminated 2–3 times during standing oestrus at 0, 12 and 24 h after the onset of oestrus. Gilts in the treatment 1–TAI group were orally administered 20 mg per day of altrenogest for 18 days and then inseminated 2–3 times during standing oestrus by conventional AI. Gilts in the treatment 2–FTAI group were synchronized like gilts in treatment 1–TAI group but then GnRH (10 μg of buserelin) was administered 120 h after the end of altrenogest treatment and fixed time artificial inseminated twice at 24 and 32 h after GnRH irrespective of the presence of oestrus or not. Conception rate of gilts in treatment 2–FTAI (87.9%) was similar to the treatment 1–TAI (94.9%) and control AI (83.3%) (P > 0.05). Conception rate in treatment 1–TAI (94.9%) was higher compared to control AI group (83.3%, P = 0.040). Farrowing rate of gilts in treatment 2–FTAI (83.8%) was similar to treatment 1–TAI (89.7%) and control AI (76.0%) (P > 0.05). Farrowing rate of treatment 1–TAI (89.7%) was higher than control AI gilts (76.0%, P = 0.033). In treatment 2–FTAI, the conception and farrowing rate of the nine gilts that were inseminated even if they were not detected in oestrus (all during warm season) was 44.4% and 44.4%, respectively. Regular return to oestrus was similar between groups (9.4%, 0.9% and 4.1% for control AI, treatment 1–TAI and treatment 2–FTAI, respectively, P > 0.05). The total number of piglets born per litter in treatment 1–TAI group was higher than control AI (13.1 ± 0.2 versus 11.6 ± 0.2, respectively, P < 0.001) and treatment 2–FTAI groups (12.2 ± 0.3, P = 0.019). The number of piglets born alive was higher in treatment 1–TAI (12.1 ± 0.3) compared to treatment 2–FTAI (11.3 ± 0.2) and control AI group (11.2 ± 0.3). The percentage of stillbirth and mummified foetus were not different between groups (P > 0.05). The present study indicated that fixed-time AI in gilts can be successfully performed by administration of altrenogest for 18 days, GnRH at 120 h after altrenogest withdrawal and then double fixed-time AI at 24 and 32 h after the administration of GnRH. Fertility metrics such as conception rate, farrowing rate and litter performances using this method were similar to gilts inseminated at oestrus with conventional AI.