Effects of breeding season and estrus synchronization protocols on the fertility of anestrus swamp buffaloes (Bubalus Bubalis)

The present study aimed to investigate the seasonal calving pattern of the swamp buffaloes and to test various estrus synchronization protocols and breeding treatments to improve the reproductive efficiency of the anestrous female buffaloes. In Study 1, we first investigated the breeding records of female buffaloes in the Phayao Animal Breeding and Research Center (PABRC) from year 2004 to 2013, aiming to compare the calving rates in three different breeding seasons, i.e. winter season (Oct. – Jan., Group 1), rainy season (Jun. – Sep., Group 2), and summer season (Feb. – Apr., Group 3). We found that the best average calving rate was observed in the winter season (74%) compared to other seasons (11-15%). Therefore, all the protocols tested in Study 2 were only compared during the winter season. In Study 2, different synchronization protocols were compared based on the resulting conception rates and the cost of estrus induction for postpartum anestrous buffaloes under field conditions during the winter season. Sixty buffalo cows were allocated to the following treatment groups by completely randomized design. The estrous cycle of buffalo cows was synchronized by Norgestomet ear implant (Norgestomet, n=30, T1), controlled internal drug release (CIDR, n=30, T2), or ovulation synchronization (Ovsynch, n=30, T3) protocols. Results from Study 1 showed that, in the winter season, buffalo cows had the highest birth rate (74.1%, 291/393), compared to the rainy (14.8%, 58/393) and summer (11.2%, 44/393) seasons. The weaning weight of buffaloes born in the rainy season was greater than their summer and winter counterparts (p < 0.05). The average daily gain (ADG) of summer-born buffaloes was higher than those born in the rainy and the winter seasons (p < 0.01). Results for Study 2 showed no differences in behavioral estrus, clear mucus discharge and dilation of cervical passage among all treatment groups (p > 0.05). However, the pregnancy rate detected by ultrasonography 90 days after TAI and the parturition rate in the Ovsynch group were all 53.3%, which was higher (p < 0.01) than CIDR (40.0%) and Norgestomet (30.0%) treated groups. Moreover, the average cost for those cows treated with CIDR protocols was higher than those with Norgestomet and Ovsynch protocols. In conclusion, breeding in winter season can result in a better birth rate in swamp buffaloes. Adoption of the Ovsynch may have triggered the ovarian activity of buffaloes and have resulted in more than half of the anestrous postpartum swamp buffaloes becoming pregnancy and parturition, as well as simultaneously lowering the cost compared to other synchronization procedures.