Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: June 2, 2000
Publication Date: July 1, 2000
Citation: Echternkamp, S.E. 2000. Comparison of steroid concentrations and insulin-like growth factor (IGF) binding protein (BP) activity in follicular fluid (FF) of cattle selected (S) and unselected (U) for dizygotic twins [abstract]. Meeting Abstract. Proceedings of the XIII Ovarian Workshop, pg. 41. Technical Abstract: Ovarian follicular development was evaluated in cattle selected on an index of ovulation and twinning rate since 1984; means for ovulation and twinning rate in S females are 1.76 and 50.4%. On day 17 (estrus = d 0), S and U cyclic females (n = 24 each) were injected with 30 mg PGF2a and ovaries were collected at slaughter at 0, 24, 48 or 72 h after PGF2a. Aliquots of FF were collected and frozen from individual follicles >5 mm. Steroids and IGF-I were measured by RIA and IGF BP activity by Western ligand blot. Numbers of small (<5 mm), medium (5-12) and large (>12 mm) antral follicles were 50% greater (P <.05) in ovaries of S vs U females. FF estradiol (E), androstenedione (A) and testosterone (T) were elevated (P <.01) in dominant vs growing vs atretic follicles and progesterone (P) was elevated (P <.01) in atretic follicles; FF E, A, T and P did not differ (P >.1) between S and U females or among slaughter times. IGF-I and BP-3 were greater (P <.01) in FF of S females but BP-2, -4 and -5 activity did not differ (P >.1) between S and U. BP-4 and -5 were absent and BP-2 decreased with increasing FF E in growing and dominant follicles r = -.46). BP-2, -4 and -5 activities were elevated (P <.01) in atretic follicles, but BP-3 was unaffected (P >.1) by follicular stage. Increased follicular development in cattle selected for twin ovulations was associated with increased blood and FF IGF-I and BP-3 but FF steroids and BP-2, -4 and -5 were unchanged.