Evidence of multiple preovulatory LH and FSH surges in mithun (Bos frontalis)

The experiment was conducted on 14 postpartum mithun (Bos frontalis) cows to establish the preovulatory LH and FSH surge patterns during estrus in peripheral circulation. Blood samples from jugular vein were collected every 2 h until 72 h and on alternate days till day 22 (day 0 = day of estrus) following the day of estrus onset. Plasma progesterone (P4), LH and FSH levels were estimated. Plasma P4 profile of the estrous cycle indicated that all the animals were ovulated following the onset of estrus. Also plasma LH and FSH concentrations were found to be significantly (p<0.01) higher around estrus. Two different preovulatory LH and FSH surge patterns were observed during the study. Pattern-1 indicated multiple and concomitant LH and FSH rises during estrus (43% animals, 6 out of 14), while pattern-2 showed multiple LH rises without concomitant FSH rises during estrus (57% animals, 8 out of 14). The basal concentrations of LH and FSH, the area under LH and FSH curves and the number of LH peak did not vary significantly during estrus between the patterns. However, the amplitude of LH and FSH peaks (p<0.05) and the number of FSH peak (p<0.01) were found to be significantly higher during estrus in pattern-1. The result indicated that the multiple preovulatory LH surges along with increased FSH activities were responsible for ovulation in mithun.