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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #162613
Title: ASSOCIATIONS AMONG CHANGES IN ESTROGEN CONCENTRATIONS IN THE FIRST WAVE DOMINANT FOLLICLE AND STEROID CONCENTRATIONS IN OTHER ANTRAL OVARIAN FOLLICLES IN BEEF COWS

Author
item Roberts, Andrew
item Echternkamp, Sherrill

Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/14/2004
Publication Date: 6/1/2004
Citation: Roberts, A.J., Echternkamp, S.E. 2004. Associations among changes in estrogen concentrations in the first wave dominant follicle and steroid concentrations in other antral ovarian follicles in beef cows [abstract]. Biology of Reproduction. 70 (Supplement):135. (Abstract #184)

Interpretive Summary: Associations among estradiol (E2) concentration in the dominant follicle (DOME2) and concentrations of E2, androstenedione (A4) and progesterone (P4) in nondominant follicles within ovaries of individual cows were evaluated. Validated RIAs were used to measure steroids in fluid from all small ([:le:]5 mm), medium, and large ([:ge:]8 mm) follicles collected from 15 cows serially slaughtered 2 to 9.5 d after estrus. Cows were classified by rising or declining DOME2, which peaked at d 4 to 5. During establishment of dominance (rising DOME2), mean E2 differed by follicle size (23.5, 9.3 and 2.6 ng/ml for 24 large, 45 medium and 192 small), and E2 in small (r=-0.35) and medium (r=-0.54) follicles was negatively associated (p< 0.01) with DOME2. After peak DOME2, E2 was less in large (13.3; n=10) and medium (4.7; n=41) but not in small (2.4; n=191) follicles, and E2 in small follicles was positively associated (r=0.16) with DOME2. During rising DOME2, A4 was positively associated with DOME2 in all size follicles, with similar A4 in small and medium (31 ng/ml), but less in large (16) follicles. After peak DOME2, A4 doubled (P<0.01) from that observed before peak DOME2, and the association between A4 and DOME2 concentration was negative for small (r=-.42) and medium (r=-0.63) follicles. Mean P4 was greater in large vs. small (150 vs. 91 ng/ml) follicles before and after peak DOME2. Mean P4 in medium follicles was low (36 ng/ml) before peak DOME2, but high after peak DOME2 (195 ng/ml). Peak P4 in all sizes occurred at DOME2 or shortly after (d 6), and P4 across sizes was associated positively with DOME2 before (r=0.15) and after (r=0.11) peak DOME2. Increased estrogenic capacity of dominant follicles was associated with decreased E2 and increased A4 and P4 in nondominant follicles, indicative of decreased aromatase activity in the nondominant population. After peak DOME2, relationships between DOME2 and steroid concentrations in nondominant follicles changed, indicating a shift in dominant follicle influence on the nondominant population.

Technical Abstract: Associations among estradiol (E2) concentration in the dominant follicle (DOME2) and concentrations of E2, androstenedione (A4) and progesterone (P4) in nondominant follicles within ovaries of individual cows were evaluated. Validated RIAs were used to measure steroids in fluid from all small ([:le:]5 mm), medium, and large ([:ge:]8 mm) follicles collected from 15 cows serially slaughtered 2 to 9.5 d after estrus. Cows were classified by rising or declining DOME2, which peaked at d 4 to 5. During establishment of dominance (rising DOME2), mean E2 differed by follicle size (23.5, 9.3 and 2.6 ng/ml for 24 large, 45 medium and 192 small), and E2 in small (r=-0.35) and medium (r=-0.54) follicles was negatively associated (p< 0.01) with DOME2. After peak DOME2, E2 was less in large (13.3; n=10) and medium (4.7; n=41) but not in small (2.4; n=191) follicles, and E2 in small follicles was positively associated (r=0.16) with DOME2. During rising DOME2, A4 was positively associated with DOME2 in all size follicles, with similar A4 in small and medium (31 ng/ml), but less in large (16) follicles. After peak DOME2, A4 doubled (P<0.01) from that observed before peak DOME2, and the association between A4 and DOME2 concentration was negative for small (r=-.42) and medium (r=-0.63) follicles. Mean P4 was greater in large vs. small (150 vs. 91 ng/ml) follicles before and after peak DOME2. Mean P4 in medium follicles was low (36 ng/ml) before peak DOME2, but high after peak DOME2 (195 ng/ml). Peak P4 in all sizes occurred at DOME2 or shortly after (d 6), and P4 across sizes was associated positively with DOME2 before (r=0.15) and after (r=0.11) peak DOME2. Increased estrogenic capacity of dominant follicles was associated with decreased E2 and increased A4 and P4 in nondominant follicles, indicative of decreased aromatase activity in the nondominant population. After peak DOME2, relationships between DOME2 and steroid concentrations in nondominant follicles changed, indicating a shift in dominant follicle influence on the nondominant population.