Different circulating progesterone concentrations during synchronization of ovulation protocol did not affect ovarian follicular and pregnancy responses in seasonal anestrous buffalo cows.

Three experiments were designed to evaluate the effect of different circulating progesterone (P4) concentrations during synchronization of ovulation protocol for timed artificial insemination of seasonal anestrous buffalo cows. In the first trial, ovariectomized cows were randomly allocated into one of three groups: using new P4 devices (G-New; n = 8), using devices previously used for 9 days (G-Used1x; n = 8), and using devices previously used for 18 days (G-Used2x; n = 8). The P4 device was maintained for 9 days, and the circulating P4 concentration was measured daily. The circulating P4 concentrations during the P4 device treatment were the lowest for G-Used2x (1.10 ± 0.04 ng/mL), intermediate for G-Used1x (1.52 ± 0.05 ng/mL), and the highest for G-New (2.47 ± 0.07 ng/mL; P = 0.001). In the second trial, 31 anestrous cows had their ovarian follicular dynamics evaluated after receiving the treatments described previously (G-New [n = 10], G-Used1x [n = 11], and G-Used2x [n = 10]). At insertion of the P4 device, cows were administered 2.0 mg of estradiol benzoate. Nine days later, the P4 device was removed and cows were administered 0.53 mg of cloprostenol sodium plus 400 IU of eCG. Forty-eight hours after P4 device removal, 10 µg of buserelin acetate was administered. There were no differences among the groups (G-New vs. G-Used1x vs. G-Used2x) in diameter of the largest follicle at P4 device removal (9.0 ± 0.8 vs. 10.1 ± 0.9 vs. 8.6 ± 0.8 mm; P = 0.35), in interval from P4 device removal to ovulation (77.1 ± 4.5 vs. 76.5 ± 4.7 vs. 74.0 ± 4.4 hours; P = 0.31), or in ovulation rate (80.0% vs. 81.8% vs. 60.0%; P = 0.51). In experiment 3, 350 anestrous cows were randomly assigned into one of the three treatments described previously (G-New, n = 111; G-Used1x, n = 121; G-Used2x, n = 118) and received a timed artificial insemination for 16 hours after buserelin treatment. The 30-day pregnancy rates did not differ among groups (55.9% vs. 55.4% vs. 48.3%; P = 0.39). Thus, the low circulating P4 concentrations released from a used P4 device efficiently control the ovarian follicular growth and had no detrimental effect on the pregnancy rates of the seasonal anestrous buffalo cows.

Ultrasonographic and endocrine aspects of follicle deviation, and acquisition of ovulatory capacity in buffalo (Bubalus bubalis) heifers.

The objectives of this study were to determine the interval from ovulation to deviation and the diameter of the dominant (DF) and largest subordinate (SF) follicles at deviation in buffalo (Bubalus bubalis) heifers. Two methods of evaluation (observed vs. calculated) were used. FSH and LH profiles encompassing follicle deviation (Experiment 1), and the follicular diameter when the DF acquired ovulatory capacity (Experiment 2) were also determined. The time of deviation and the diameter of the DF and the largest SF at deviation did not differ between observed and calculated methods. Overall, follicle deviation occurred 2.6 ± 0.2d (mean ± SEM) after ovulation, and the diameters of the DF and SF at deviation were 7.2 ± 0.2 and 6.4 ± 0.2mm, respectively. No changes in plasma levels of FSH or LH were observed (P=0.32 and P=0.96, respectively). Experiment 2 was conducted in two phases according to the diameter of the DF during the first wave of follicular development at the time of LH challenge (25mg of pLH). In the first phase, follicles ranging from 5.0 to 6.0mm (n=7), 6.1 to 7.0mm (n=11), or 7.1 to 8.0mm (n=9) were used, and in the second phase, follicles ranging from 7.0 to 8.4mm (n=10), 8.5 to 10.0mm (n=10), or 10.1 to 12.0mm (n=9) of diameter were used. After the pLH treatment, the DF was monitored by ultrasonography every 12h for 48h. No ovulations occurred in heifers in the first phase. However, in the second phase, an effect of follicular diameter was observed on ovulation rate [7.0-8.4mm (0.0%, 0/10), 8.5-10.0mm (50.0%, 5/10), and 10.0-12.0mm (55.6%, 5/9)]. In summary, follicle deviation occurred 2.6d after ovulation in buffalo (B. bubalis) heifers, when the diameters of the DF and SF were 7.2 and 6.4mm, respectively. No significant changes in plasma concentrations of FSH or LH were detected. Finally, the acquisition of ovulatory capacity occurred when the DF reached 8.5mm in diameter.