Follicle and hormone dynamics in single versus double ovulating heifers.
Follicles > or = 5 mm were ablated at 4 day post-ovulation in heifers to induce a follicular wave, and prostaglandin F(2alpha) was given at day 6 to increase the incidence of double ovulations. Follicle diameters and plasma hormone concentrations were compared between single ovulators (n=12) and double ovulators (n=8). In double ovulators, the interval from follicle deviation to the peak of the pre-ovulatory LH surge was shorter (1.9+/-0.2 vs 2.5+/-0.2 days; P<0.02) and diameter of the largest pre-ovulatory follicle was smaller (12.2+/-0.5 vs 13.3+/-0.3 mm; P<0.02). The LH concentrations of the pre-ovulatory surge did not differ between single and double ovulators for 24 h on each side of the peak. When data were normalised to LH peak, the peak of the pre-ovulatory FSH and oestradiol (E(2)) surges occurred in synchrony with the peak of LH surge for both groups. Concentration of FSH for 24 h on each side of the peak showed a group effect (P<0.0001) from lower concentration in the double ovulators. A group-by-hour interaction (P<0.008) for E(2) reflected greater concentration in the double ovulators before and at the peak. Results indicated that two pre-ovulatory follicles resulted in an earlier and greater E(2) increase, leading to lower FSH concentration, an earlier LH surge, and ovulation at a smaller diameter. In conclusion, the difference in hormone concentrations during the pre-ovulatory period was an effect rather than a cause of double ovulations.
Palhao
M P
MP
Eutheria Foundation, Cross Plains, Wisconsin 53528, USA.
Beg
M A
MA
Rodrigues
M T
MT
Ginther
O J
OJ
D000818:Animals; D002417:Cattle / Q000097:blood / Q000378:metabolism / Q000502:physiology; D002452:Cell Count; D004958:Estradiol / Q000097:blood / Q000378:metabolism; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000378:metabolism; D006728:Hormones / Q000097:blood / Q000378:metabolism*; D007700:Kinetics; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism; D008954:Models, Biological; D006080:Ovarian Follicle / Q000166:cytology* / Q000378:metabolism*; D010060:Ovulation / Q000097:blood / Q000378:metabolism* / Q000502:physiology; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000097:blood / Q000378:metabolism; D011374:Progesterone / Q000097:blood / Q000378:metabolism
D006728:Hormones; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone