|Lindsey, Brad - UNIVERSITY OF NEBRASKA|
|Kinder, James - UNIVERSITY OF NEBRASKA|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: February 1, 1999
Publication Date: N/A
Technical Abstract: Treatment with growth hormone stimulates bovine ovarian follicular development while cattle selected for natural twin ovulations had higher systemic IGF-I. Present objective was to determine the relationship between IGF-I and FSH in the initiation of ovarian follicular development by follicle ablation. Follicles >/= 5 mm in diameter were ablated transvaginally in 24 cyclic crossbred cows on d 7 or 8 (estrus=d 0). Blood samples were collected at 12-h intervals via a jugular vein cannula beginning just before ablation and continuing for 96 h after ablation. Plasma was collected and stored at -4 C until assayed. IGF-I was measured by RIA subsequent to acid-ethanol extraction; FSH and LH were measured directly using a double-antibody RIA. Circulating concentrations of both IGF-I and FSH were elevated (P<.01) within 12 h after ablation. Peak mean concentration of IGF-I (61.3+/-5.5 ng/ml) occurred at 24 h after ablation and returned to baseline (47.6+/-5.5 ng/ml) by 72 h. Peak mean concentration of FSH (70.3+/-5.7 ng/ml) occurred at 24 h and returned to baseline (31.1+/-5.7 ng/ml) by 72 h. The correlation between plasma IGF-I and FSH concentrations for the 96-h period was r=.76 (P<.01). Systemic LH concentrations were unaffected (P>.1) by follicle ablation. Results suggest that removal of all medium and large follicles by ablation enhances IGF-I secretion, which may assist the initiation of a new ovarian follicular wave by FSH.