Animal Science Research and Review

Special Circular 161-99

Effects of Season and Selection for High vs. Low Blood Serum Insulin-Like Growth Factor I Concentration on Reproductive Performance of Bulls

A. Yilmaz*,
M. E. Davis^{* 1},
R. C. M. Simmen⁺

*The Ohio State University Department of Animal Sciences
⁺University of Florida Department of Animal Science

Abstract

The objectives of this study were to examine seasonal effects and differences in scrotal circumference, sperm motility, and percentage of normal sperm cells between two lines of Angus beef cattle selected for high vs. low blood serum IGF-I concentration. Data were obtained from an ongoing experiment involving 100 spring-calving (50 high and 50 low line) and 100 fall-calving (50 high and 50 low) purebred Angus cows. Scrotal circumference was significantly larger in (P=) spring-born bulls than in fall-born bulls, but did not differ between high and low IGF-I line bulls (P = 0.079). Percentage of motile sperm cells did not differ between high and low line bulls (P = 0.50). Fall-born bulls had higher sperm motility than spring-born bulls in every year in which motility was evaluated. Percentage of normal sperm cells did not differ between high and low line bulls (P = 0.56); however, fall-born bulls had a significantly higher percentage of normal sperm cells. Regression coefficients for the non-linear relationship between scrotal circumference and IGF28, IGF42, and IGF56 were negative (P = 0.02, 0.07, and 0.08, respectively). The regression coefficient for the non-linear relationship between percentage of normal sperm cells and IGF56 was negative and significant (P = 0.03). Regression coefficients for the non-linear relationships of scrotal circumference, percent sperm motility, and percentage of normal sperm cells with mean IGF-I concentrations were negative and were either significant or approached significance (P = 0.01, 0.16 and 0.04, respectively). Thus, scrotal circumference, percent sperm motility and percentage of normal sperm cells are related to blood serum IGF-I concentration in Angus bulls.

¹For more information contact at: The Ohio State University, 221 Plumb Hall, 2027 Coffey Road, Columbus, OH, 43210; 614-292-4984; fax: 614-292-2929; e-mail: davis.28@osu.edu