COUNTERACTION OF THE FOLLICULAR INHIBITORY EFFECT OF FOLLICULAR-FLUIDBY ADMINISTRATION OF FSH IN HEIFERS

The hypothesis that a factor in follicular fluid suppresses follicular growth independently of reduced systematic FSH concentrations in catt le was tested in a 2 x 2 factorial designed experiment (n = 5 heifers group(-1)). Treatment, at 12-h intervals, began on day 0 (ovulation) a nd ended on day 1. Mean (+/- SEM) diameter of the largest follicle, av eraged over all days, and maximum diameter attained on days 0-9 was sm aller (P < 0.05) in heifers given follicular fluid (8.4 +/- 0.4 and 12 .4 +/- 1.0 mm, respectively) than in heifers given either saline (10.3 +/- 0.6 and 14.8 +/- 0.6 mm) or follicular fluid plus FSH (10.7 +/- 0 .6 and 16.8 +/- 0.4 mm). The day-to-day mean diameter profiles of both the largest and second-largest follicles for days 0-9 were similar am ong heifers given saline, follicular fluid plus FSH, and FSH alone, wh ereas the follicle profile was reduced in heifers given follicular flu id alone. Mean follicle diameters were smaller (P < 0.05) on days 4-9 and days 2 and 5 in heifers given follicular fluid than in heifers giv en either saline or follicular fluid plus FSH. The results did not sup port the hypothesis, since exogenous FSH overrode follicular inhibitio n induced by follicular-fluid treatment.