Follicle Selection in Cattle: Relationships among Growth Rate, Diameter Ranking, and Capacity for Dominance

• Published in: Biology of reproduction Vol. 65; no. 2; pp. 345 - 350
• Main Authors: GINTHER, O. J, BERGFELT, D. R, BEG, M. A, KOT, K
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01-08-2001
• Subjects: Animals; Biological and medical sciences; Cattle; Female; Follicle Stimulating Hormone - blood; Fundamental and applied biological sciences. Psychology; Kinetics; Mammalian female genital system; Morphology. Physiology; Ovarian Follicle - anatomy & histology; Ovarian Follicle - diagnostic imaging; Ovarian Follicle - physiology; Ovulation; Suction; Ultrasonography; Vertebrates: reproduction; Growth; Ox; Dominance; Gonadotropin; Ovary; Vertebrata; Mammalia; Adenohypophyseal hormone; Female genital system; Artiodactyla; Morphometry; Ovarian follicle; Ungulata; Diameter; Follicle stimulating hormone
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod65.2.345

Follicles of wave 1 were designated F1, F2, and so forth, according to descending diameter at the expected (F1, ≥8.2 mm) or
observed beginning of deviation (Hour 0), as indicated by a reduction in growth rate of F2. During Hours −24 to 0 (experiment
1; n = 34 waves) and Hours −16 to 0 (experiment 2; n = 21), F1 and F2 grew in parallel (no significant differences). During
Hours −16 to 0, growth rate was greater ( P < 0.05) for F1 (1.4 ± 0.1 mm/16 h) and F2 (1.0 ± 0.1) than for F3 (0.6 ± 0.1) and F4 (0.5 ± 0.1). During Hours 0 to 16, growth
rate was greater ( P < 0.05) for F1 (1.4 ± 0.2 mm/16 h) than for F2 (0.1 ± 0.1), F3 (0.1 ± 0.1), and F4 (0.1 ± 0.2). In experiment 1, zero, one,
two, or three largest follicles were ablated by aspiration of contents at Hour 0 (n = 7/group). For heifers with a single
dominant follicle, the dominant follicle formed from the largest retained follicle more often when it was >7.0 mm (14 of 15)
than when it was <7.0 mm (0 of 10). When the retained follicles were <7.0 mm, the first follicle to reach 7.0 mm became dominant
in seven of eight heifers. Mean hour of observed deviation (occurring after Hour 0 in the ablation groups) increased progressively
in groups with increasing number of ablated follicles. Plasma concentrations of FSH for groups with one, two, or three ablated
follicles increased to a similar extent between Hours 0 and 12. Results supported the following: 1) during the 24 h before
the beginning of deviation, small follicles grew more slowly than large follicles and the largest follicles grew in parallel;
2) after ablation of large follicles, the small retained follicles did not deviate until one reached a diameter characteristic
of the beginning of deviation; 3) the potential for dominance at the expected beginning of deviation was greatest for the
largest follicle and decreased progressively for the smaller follicles but only when the retained follicles were >7.0 mm;
and 4) the three largest subordinate follicles began to deviate simultaneously.