Journal of Animal Science, Vol 78, Issue 6 1564-1567, Copyright © 2000 by American Society of Animal Science

JOURNAL ARTICLE

Evaluation of numbers of microscopic and macroscopic follicles in cattle selected for twinning

R. A. Cushman, V. S. Hedgpeth, S. E. Echternkamp and J. H. Britt
Department of Anatomy, Physiological Sciences and Radiology, North Carolina State University, Raleigh 27606, USA.

We hypothesized that the number of microscopic follicles present in the ovaries of cattle selected for twin births (Twinner) would be greater than in the ovaries of contemporary Controls. Ovaries were collected from seven Control and seven Twinner cows at slaughter. The number of Small (1 to 3.9 mm), Medium (4 to 7.9), and Large (> 8 mm) surface follicles was counted and one ovary was fixed for histological evaluation. Fifty to sixty consecutive 6-microm slices were taken from a piece of cortical tissue, approximately 1 cm x 1 cm in area, located between the surface follicles. Microscopic follicles were classified as primordial (oocyte surrounded by a single layer of squamous pregranulosa cells), primary (oocyte surrounded by a single layer of one or more cuboidal granulosa cells), secondary (oocyte surrounded by two or more layers of granulosa cells), or tertiary (oocyte surrounded by multiple layers of granulosa cells with initiation of antrum formation to < or = 1 mm in diameter). The total number of follicles was counted in 200 fields (2 mm x 2 mm) per ovary. A field containing no follicles was classified as empty. There were significantly more secondary follicles in Twinner compared with Control ovaries (12.9 vs 6.3; P < .05). Twinners also tended to have more small surface follicles (35.4 vs 49.0; P < 0.1). We conclude that ovaries of Control and Twinner cows do not differ in the number of primordial follicles or in the number of follicles activated into the growing pool; however, Twinner cows are able to maintain more growing follicles at the secondary and subsequent stages of development.

This article has been cited by other articles:

				S. E. Echternkamp, R. A. Cushman, and M. F. Allan Size of ovulatory follicles in cattle expressing multiple ovulations naturally and its influence on corpus luteum development and fertility J Anim Sci, November 1, 2009; 87(11): 3556 - 3568. [Abstract] [Full Text] [PDF]

				R. A. Cushman, M. F. Allan, L. A. Kuehn, W. M. Snelling, A. S. Cupp, and H. C. Freetly Evaluation of antral follicle count and ovarian morphology in crossbred beef cows: Investigation of influence of stage of the estrous cycle, age, and birth weight J Anim Sci, June 1, 2009; 87(6): 1971 - 1980. [Abstract] [Full Text] [PDF]

				D. S. Burns, F. Jimenez-Krassel, J. L.H. Ireland, P. G. Knight, and J. J. Ireland Numbers of Antral Follicles During Follicular Waves in Cattle: Evidence for High Variation Among Animals, Very High Repeatability in Individuals, and an Inverse Association with Serum Follicle-Stimulating Hormone Concentrations Biol Reprod, July 1, 2005; 73(1): 54 - 62. [Abstract] [Full Text] [PDF]

				S. E. Echternkamp, A. J. Roberts, D. D. Lunstra, T. Wise, and L. J. Spicer Ovarian follicular development in cattle selected for twin ovulations and births J Anim Sci, February 1, 2004; 82(2): 459 - 471. [Abstract] [Full Text] [PDF]