Exogenous progesterone-dependent modulation in the follicular dynamics of Bos indicus cattle undergoing repeated ovum pick-up sessions.

The objective of the present study was to evaluate the role of serum progesterone (P4) in follicular dynamics, oocytes' recovery and quality and their in vitro developmental competence during consecutive ovum pick-up (OPU) sessions in Bos indicus dairy cows. Wave-synchronized Sahiwal cattle (n = 20) were randomly divided into treatment (n = 10) and control (n = 10) groups. CIDR was used as a source of external progesterone in the treatment group. Four consecutive OPU sessions at 96-hr intervals were conducted and repeated ultrasonography at 12-hr intervals was done to monitor follicular dynamics. The viable oocytes were processed for IVC following IVM and IVF until day 7. The serum P4 concentrations in the P4 and control groups were recorded as 2.31 ± 0.059 versus.0.32 ± 0.065 ng/ml, respectively (p < .05). In the treatment group, the total number of recorded follicles was higher (p < .05; 12.05 ± 0.37 versus. 10.87 ± 0.40), whilst the growth rate (mm/day) of follicles was lower (p > .05). Per session recovered oocytes (5.31 ± 0.19 versus. 3.58 ± 0.21; p < .0001) and recovery rate (54.23 versus. 42.53%; p < .05) were also higher in the treatment group compared to control. Similarly, the viable oocytes (4.54 ± 0.187 versus. 3.06 ± 0.199) and the number of grade I and II oocytes per session (3.37 ± 0.196 versus. 2.06 ± 0.21) were higher (p < .05) in the treatment group compared with the control group. However, the nuclear maturation, cleavage, and blastocyst rate did not differ (p > .05) between the groups. Taken together, during OPU sessions, serum P4 improves oocytes' recovery and quality, whilst does not affect the in vitro developmental competence of recovered oocytes.