Effects of a dominant follicle on ovarian follicular dynamics during the oestrous cycle in heifers.
Two hypotheses were tested: (1) a dominant follicle causes regression of its subordinate follicles, and (2) a dominant follicle during its growing phase suppresses the emergence of the next wave. Cyclic heifers were randomly assigned to one of four groups (6 heifers/group): cauterization of the dominant follicle of Wave 1 or sham surgery (control) on Day 3 or Day 5 (day of ovulation = Day 0). Ultrasonic monitoring of individually identified follicles was done once daily throughout the interovulatory interval. The onset of regression (decreasing diameter) of the largest subordinate follicle of Wave 1 was delayed (P less than 0.01) by cauterization of the dominant follicle of Wave 1 on Day 3 compared to controls (mean onset of regression, Days 10.8 +/- 2.1 vs 4.3 +/- 0.4). Cauterization of the dominant follicle of Wave 1 on Days 3 or 5 caused early emergence (P less than 0.01) of Wave 2 when compared to controls (Day-3 groups: Days 5.5 +/- 0.4 vs 9.6 +/- 0.7; Day-5 groups: Days 7.0 +/- 0.3 vs 9.1 +/- 0.4). The results supported the two hypotheses. In addition, cauterization of the dominant follicle of Wave 1 on Days 3 or 5 increased the incidence of 3-wave interovulatory intervals.
Ko
J C
JC
Department of Veterinary Science, University of Wisconsin-Madison 53706.
Kastelic
J P
JP
Del Campo
M R
MR
Ginther
O J
OJ
D000818:Animals; D002417:Cattle / Q000502:physiology*; D002425:Cautery; D004971:Estrus / Q000502:physiology*; D005260:Female; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000254:growth & development*; D014463:Ultrasonography