Effect of progesterone administration during growing phase of first dominant follicle on follicular wave pattern in buffalo heifers

In buffaloes, like other domestic mammals, antral follicles develop in a wave-like pattern. Factors predictive of a particular follicular wave pattern are yet to be identified. In this study, we examined the preponderance of 2- versus 3-wave patterns in 46 interovulatory intervals (IOIs) from 36 buffalo heifers, in which a subset of 10 heifers was scanned for 2 consecutive IOIs to record the repeatability of follicular wave pattern. Two-wave pattern was detected in 63.0% and 3-wave follicular pattern in 27.0% IOIs. The dominant follicles (DF) of both wave 1 as well as the ovulatory wave attained a smaller (P < 0.05) maximum diameter in 3-wave cycle as compared to 2-wave cycle. The mean duration of IOI was significantly shorter in 2-wave compared to three-wave cycles (20.5 ± 0.3 vs. 22.3 ± 0.2 days; P < 0.05). Out of 10 buffalo heifers, 7 displayed non-alternating patterns and 3 had alternating follicular wave patterns. We also tested the hypothesis that progesterone administration during early IOI results in increased preponderance of 3-wave pattern and heifers inseminated after ovulation of the third wave DF will have greater fertility. Sixteen heifers subjected to progesterone treatment from D0 (day of ovulation) in a decreasing dose until D5 were compared with control heifers (n = 10). Progesterone treatment significantly reduced the maximum diameter of DF of wave 1 (P < 0.001), whereas the mean duration of IOI remained unchanged (P > 0.05) between the two groups. Progesterone administration during early IOI significantly increased the proportion of 3-wave cycles as compared to control (P < 0.05). The hypothesis that progesterone administration during IOI results in increased preponderance of 3-wave pattern was supported. However, no change in fertility was recorded in progesterone-treated heifers (7 pregnant out of 16; 43.8%) as compared to untreated control heifers (4 out of 10 heifers; 40.0%). In summary, progesterone administration in buffalo heifers during the growing phase of wave 1 resulted in greater preponderance of 3-wave follicular patterns, with no significant effect on fertility.

Defective secretion of Prostaglandin F2α during development of idiopathic persistent corpus luteum in mares

Five mares that developed idiopathic persistent corpus luteum (PCL) were compared with 5 mares with apparently normal interovulatory intervals (IOIs). Progesterone (P4) and a metabolite of prostaglandin F2α (PGFM) were assayed daily beginning on the day of ovulation (Day 0). Transition between the end of an initial progressive P4 increase and the beginning of a gradual decrease in P4 occurred on mean Day 6. The gradual decrease in P4 between Days 6 and 12 was less (approached significance, P < 0.06) in the PCL group than in the IOI group. The P4 concentration on Day 12 (before luteolysis in IOI group) was greater (P < 0.05) in the PCL group than in the IOI group. In a post hoc comparison, an interaction (P < 0.04) of group by day for Days 4 to 7 indicated that the end of the progressive increase in P4 was temporally associated with a transient increase in concentration of PGFM in IOI mares but not in PCL mares. Complete luteolysis (P4 < 1 ng/mL) occurred in the IOI mares on Days 13 to 15. Partial luteolysis (mean P4 decrease, 62%) occurred in 3 of the 5 PCL mares. Normalization to the day at the end of the most pronounced P4 decrease in the IOI mares and in the 3 PCL mares with partial luteolysis resulted in a day-by-group interaction (P < 0.05) for PGFM concentration. The interaction was partly from lower PGFM concentration on the day at the end of the pronounced P4 decrease in the 3 PCL mares than in the IOI mares. The peak of a transient PGFM increase and the day at the end of the most pronounced decrease in P4 were synchronized in each IOI mare but not in any of the 3 PCL mares. In the other 2 PCL mares, partial luteolysis did not occur, and a transient increase in PGFM was not apparent. Results tentatively indicated that the relationship between P4 and PGFM may be altered as early as Day 6 in PCL mares and supported the hypothesis that prostaglandin F2α secretion is defective in mares with idiopathic PCL.