Synchronization of estrus and artificial insemination in buffalo heifers by using two different protocols.

In Italy, because of the application of the out of breeding season mating (OBMS) technique in buffalo species, there are some months during which few deliveries, and consequently scanty milk production, are present. Buffalo heifers are lesser sensible to the seasonality compared to pluriparous animals and hence can be inseminated also in a period characterised by increasing day length, increasing milk production in some periods of the year. Few studies have been carried out in order to verify the most efficient method for synchronization of estrus and artificial insemination (AI) in buffalo heifers. The aim of this study was to compare two methods of synchronization of estrus largely used in buffalo species. The trial was carried out on 146 Italian Mediterranean buffalo heifers 781±103 days old and characterised by a body weight of at least 380 kg. Animals were divided in two groups according to their age and body weight. Heifers in group A (n=67) were synchronized by using the Ovsynch-TAI Program, which consists of 12 g buserelin acetate on Day 0, 0.524 mg PGF2α on Day 7 and 12 g buserelin acetate on Day 9, whereas animals in Group B (n=68) received a double injection of 0.524 mg of PGF2α 12 days apart. Each heifer was inseminated twice, 16 and 40 h after the second injection of GnRH in Group A and 60 and 84 h after the second injection of PGF2α in Group B. On day 26 post-insemination heifers underwent trans-rectal ultrasonography examination, in order to assess pregnancies, that were confirmed on Day 45 by rectal palpation. Statistical analysis was performed by chi-square test. Synchronization rate was similar in the two groups (93.1 vs. 91.9, respectively in Group A and B). No differences in terms of pregnancy rate were recorded between the two treatments. A higher although not statistically significant pregnancy rate was observed in Group B, which showed also a lower incidence of early embryo mortality. Similar results in terms of pregnancy rate in buffalo heifers have been previously reported. In conclusion both protocols can be used in order to synchronize buffalo heifers and concentrate the deliveries in some periods of the year.