Ovarian response in water buffaloes induced to ovulate outside the breeding season

The study evaluated the effect of two hormonal protocols on the ovarian activity and pregnancy rate of water buffaloes ( Bubalus bubalis ) outside the breeding season. Twenty multiparous Murrah × Mediterranean buffaloes were included. The protocols used were the following: 1) GnRH (n = 10): 100 µg gonadorelin IM (Day 0), 500 µg cloprostenol IM (Day 7), 100 µg gonadorelin IM (Day 9) and fixed time artificial insemination (FTAI) 18 h after the second GnRH; 2) P4 + eCG (n = 10): intravaginal progesterone (P4) device + 2 mg estradiol benzoate (Day 0), device removal + 500 µg cloprostenol + 400 IU eCG (Day 10), 10 µg buserelin acetate (Day 12) and FTAI 54 h after device removal. The numbers of small (< 4 mm), medium (4.1-8 mm) and large (> 8.1 mm) follicles (follicular population) were counted through ultrasonography. The diameters of the largest follicle (maximum follicular diameter; MFD) and corpus luteum (CL) were evaluated. Blood samples were obtained on Days 0, 9, 17, 24 and 31 in the GnRH group and on Days 0, 10, 19, 26 and 33 in the P4 + eCG group to determine serum P4 concentrations. No differences were found between groups in follicular population, MFD and CL diameter. The presence of CL and P4 concentrations were greater in the P4 + eCG group. Only females from the P4 + eCG group became pregnant and P4 concentrations were > 3 ng/ml on Days 26 and 33. In conclusion, the P4 + eCG protocol was effective to induce ovulation and achieve pregnancy in buffalo cows outside the breeding season under tropical conditions.