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1 September 2001 Follicle Selection in Cattle: Follicle Deviation and Codominance Within Sequential Waves
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Follicle deviation during bovine follicular waves is characterized by continued growth of a developing dominant follicle and reduction or cessation of growth of subordinate follicles. Characteristics of follicle deviation for waves with a single dominant follicle were compared between wave 1 (begins near ovulation; n = 15) and wave 2 (n = 15). Follicles were defined as F1 (largest), F2, and F3, according to maximum diameter. No mean differences were found between waves for follicle diameters at expected deviation (F1, ≥8.5 mm; Hour 0) or observed deviation or in the interval from follicle emergence at 4.0 mm to deviation. For both waves, circulating FSH continued to decrease (P < 0.05) after Hour 0, estradiol began to increase (P < 0.05) at Hour 0, and immunoreactive inhibin began to decrease (P < 0.05) before Hour 0. A transient elevation in circulating LH reached maximum concentration at Hour 0 (P < 0.01) in both waves and was more prominent (P < 0.0001) for wave 1. Waves with codominant follicles (both follicles >10 mm) were more common (P < 0.02) for wave 1 (35%) than for wave 2 (4%). Codominants (n = 6) were associated with more (P < 0.05) follicles ≥4 mm and a greater concentration (P < 0.04) of circulating estradiol at Hours −48 to −8 than were single dominant follicles (n = 15). A mean transient increase in FSH and LH occurred in the codominant group at Hour −24 and may have interfered with deviation of F2. In codominant waves, deviation of F3 occurred near Hour 0 (F1, approximately 8.5 mm). A second deviation involving F2 occurred in four of six waves a mean of 50 h after the F3 deviation and may have resulted from a greater suppression (P < 0.05) of FSH in the codominant group after Hour 0. In conclusion, follicle or hormone differences were similar for waves 1 and 2, indicating that the deviation mechanisms were the same for both waves. Waves that developed codominant follicles differed in hormone as well as follicle dynamics.

L. J. Kulick, D. R. Bergfelt, K. Kot, and O. J. Ginther "Follicle Selection in Cattle: Follicle Deviation and Codominance Within Sequential Waves," Biology of Reproduction 65(3), 839-846, (1 September 2001).
Received: 5 March 2001; Accepted: 1 April 2001; Published: 1 September 2001

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