Comparative Reproductive Response of Bulgarian Murrah Buffaloes to Ovsynch Protocol Across Breeding and Non-Breeding Seasons

The aim of this study was to evaluate Ovsynch protocol efficiency and the effect of season on conception rates in Bulgarian Murrah buffaloes. The Ovsynch protocol was applied in 32 buffaloes during the breeding period (Group I) and 15 buffaloes during the non-breeding season (Group II). Ultrasound scans were performed on day -10, day 0 and day 10 to detect ovarian structures and on day 35 after fixed-time artificial insemination for early pregnancy diagnosis. Blood samples were collected on the 7th and 17th day for assay of serum progesterone concentrations and detection of ovulation stage. Discharge was observed in 59.4% (19/32) of the buffaloes from the first and 33.3% (5/15) from the second group. Pregnancy was detected in 52.6% (10/19) of the animals during the breeding season and in 40.0% (2/5) during the non-breeding season. Openness of the cervical canal was registered in 53.1% (17/32) of animals from first group and in 20.0% (3/15) from the second one, whereas pregnancy was detected in 23.5% (4/17) and 33.3%, (1/3) respectively. During the breeding season the ovulation rate was detected in 71.9% (23/32) of the buffaloes after the first GnRH treatment, and in 81.3% (26/32) after the second one. In the second group, percentages were lower-53.3% (8/15) and 66.7% (10/15). On the 35^th day, pregnancy was detected in 46.9% (15/32) of the buffaloes during the breeding season and 20.0% (3/15) during non-breeding season. Our results showed that the Ovsynch protocol is efficient for estrus synchronisation and fertilisation in both season. The highest ovulation rates are obtained in buffaloes with CL and follicle ≤10 mm at starting of protocol. Ultrasound determination of ovarian structures before starting the Ovsynch protocol will increase ovulation and pregnancy rates.