HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gastal, E.L. Articles by Ginther, O.J. Search for Related Content PubMed PubMed Citation Articles by Gastal, E.L. Articles by Ginther, O.J. Agricola Articles by Gastal, E.L. Articles by Ginther, O.J.

Experimental Assumption of Dominance by a Smaller Follicle and Associated Hormonal Changes in Mares¹

^a Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison, Wisconsin 53706 ^b Department of Animal Science, Federal University of Viçosa, Viçosa, MG 31570-000, Brazil

A two-follicle model was used to study the nature of selection of the dominant follicle in mares by ablating neither or one of the two follicles on the day the larger follicle reached 20 mm (Day 0). The larger follicle became the dominant follicle in all mares in which both follicles (n = 8) or only the larger follicle (n = 10) was retained. When only the smaller follicle (n = 9) was retained, it became dominant and ovulated in six mares and became atretic in three mares; the difference in diameter between the two follicles on Day 0 was less (p < 0.01) in mares in which the retained smaller follicle grew and ovulated (2.2 ± 0.6 mm) than in the mares in which the follicle became atretic (5.9 ± 1.2 mm). A decline (p < 0.0001) in FSH concentrations occurred over Days -4 (8.4 ± 0.7 ng/ml) to 0 (5.9 ± 0.3 ng/ml), averaged over all groups, and the decline continued for several more days in the groups with both follicles or with only the larger follicle retained. In the group with only the smaller follicle retained, compared to the group with both follicles retained, FSH concentrations and diameter of the smaller follicle increased between Days 0 and 1 (significant interaction for each end point). After Day 1, FSH concentrations continued to increase when the smaller retained follicle became atretic; concentrations decreased when the smaller retained follicle became dominant. An increase (p < 0.0001) in LH concentrations occurred over Days -4 (12.2 ± 1.1 pg/ml) to 0 (21.1 ± 2.0 pg/ml), averaged over the three groups. In 23 of 27 mares, a transient peak in LH concentrations occurred within 2 days of Day 0. In the groups with both follicles or with only the larger follicle retained, an increase (p < 0.0001) in systemic estradiol concentrations occurred between Day 0 (5.3 ± 0.6 pg/ml) and Day 2 (7.5 ± 0.4 pg/ml). When only the smaller follicle was retained, estradiol did not begin to increase until Day 2, and it increased only when the retained follicle grew and became dominant. The beginning of an increase in estradiol and continued decrease in FSH at the expected beginning of deviation were attributable to the future dominant follicle; there was no indication that the smaller follicle was involved.

¹ Research supported by Equiservices Publishing and by EquiCulture, Inc., Cross Plains, WI. E.L.G. and M.O.G. were supported by the Federal University of Viçosa and by a CAPES scholarship, Brazil.

² Correspondence: O.J. Ginther, Department of Animal Health and Biomedical Sciences, University of Wisconsin-Madison, 1656 Linden Drive, Madison, WI 53706. FAX: 608 262 7420; ojg{at}ahabs.wisc.edu

This article has been cited by other articles:

				O.J Ginther, M.D Utt, M.A Beg, E.L Gastal, and M.O Gastal Negative Effect of Estradiol on Luteinizing Hormone Throughout the Ovulatory Luteinizing Hormone Surge in Mares Biol Reprod, September 1, 2007; 77(3): 543 - 550. [Abstract] [Full Text] [PDF]

				M A Beg and O J Ginther Follicle selection in cattle and horses: role of intrafollicular factors. Reproduction, September 1, 2006; 132(3): 365 - 377. [Abstract] [Full Text] [PDF]

				O J Ginther, M A Beg, E L Gastal, M O Gastal, A R Baerwald, and R A Pierson Systemic concentrations of hormones during the development of follicular waves in mares and women: a comparative study Reproduction, September 1, 2005; 130(3): 379 - 388. [Abstract] [Full Text] [PDF]

				O.J. Ginther, E.L. Gastal, M.O. Gastal, and M.A. Beg Regulation of Circulating Gonadotropins by the Negative Effects of Ovarian Hormones in Mares Biol Reprod, August 1, 2005; 73(2): 315 - 323. [Abstract] [Full Text] [PDF]

				O J Ginther, E L Gastal, M O Gastal, and M A Beg In vivo effects of pregnancy-associated plasma protein-A, activin-A and vascular endothelial growth factor on other follicular-fluid factors during follicle deviation in mares Reproduction, April 1, 2005; 129(4): 489 - 496. [Abstract] [Full Text] [PDF]

				E L Gastal, M O Gastal, M A Beg, and O J Ginther Interrelationships among follicles during the common-growth phase of a follicular wave and capacity of individual follicles for dominance in mares Reproduction, October 1, 2004; 128(4): 417 - 422. [Abstract] [Full Text] [PDF]

				O.J. Ginther, E.L. Gastal, M.O. Gastal, and M.A. Beg Critical Role of Insulin-Like Growth Factor System in Follicle Selection and Dominance in Mares Biol Reprod, May 1, 2004; 70(5): 1374 - 1379. [Abstract] [Full Text] [PDF]

				O.J. Ginther, D.R. Bergfelt, M.A. Beg, C. Meira, and K. Kot In Vivo Effects of an Intrafollicular Injection of Insulin-Like Growth Factor 1 on the Mechanism of Follicle Deviation in Heifers and Mares Biol Reprod, January 1, 2004; 70(1): 99 - 105. [Abstract] [Full Text] [PDF]

				A. R. Baerwald, G. P. Adams, and R. A. Pierson Characterization of Ovarian Follicular Wave Dynamics in Women Biol Reprod, September 1, 2003; 69(3): 1023 - 1031. [Abstract] [Full Text] [PDF]

				O.J. Ginther, C. Meira, M.A. Beg, and D.R. Bergfelt Follicle and Endocrine Dynamics During Experimental Follicle Deviation in Mares Biol Reprod, September 1, 2002; 67(3): 862 - 867. [Abstract] [Full Text] [PDF]

				F.X. Donadeu and O.J. Ginther Changes in Concentrations of Follicular Fluid Factors During Follicle Selection in Mares Biol Reprod, April 1, 2002; 66(4): 1111 - 1118. [Abstract] [Full Text] [PDF]

				O.J. Ginther, M.A. Beg, D.R. Bergfelt, F.X. Donadeu, and K. Kot Follicle Selection in Monovular Species Biol Reprod, September 1, 2001; 65(3): 638 - 647. [Abstract] [Full Text] [PDF]

				D.R. Bergfelt, E.L. Gastal, and O.J. Ginther Response of Estradiol and Inhibin to Experimentally Reduced Luteinizing Hormone During Follicle Deviation in Mares Biol Reprod, August 1, 2001; 65(2): 426 - 432. [Abstract] [Full Text] [PDF]

				O.J. Ginther, D.R. Bergfelt, M.A. Beg, and K. Kot Follicle Selection in Cattle: Role of Luteinizing Hormone Biol Reprod, January 1, 2001; 64(1): 197 - 205. [Abstract] [Full Text]

				O.J. Ginther, D.R. Bergfelt, L.J. Kulick, and K. Kot Selection of the Dominant Follicle in Cattle: Role of Two-Way Functional Coupling Between Follicle-Stimulating Hormone and the Follicles Biol Reprod, April 1, 2000; 62(4): 920 - 927. [Abstract] [Full Text]

				E.L. Gastal, D.R. Bergfelt, G.P. Nogueira, M.O. Gastal, and O.J. Ginther Role of Luteinizing Hormone in Follicle Deviation Based on Manipulating Progesterone Concentrations in Mares Biol Reprod, December 1, 1999; 61(6): 1492 - 1498. [Abstract] [Full Text]