The objective of this study was to estimate genetic and environmental variances and heritabilities for body measurements, daily gain, semen volume and semen concentration of young Simmental bulls. In addition, genetic trends for those traits were analyzed. Data utilized in this study consisted of records of 955 young Simmetal bulls born from 1974 to 1995 and were provided by the Performance Test Station - Varazdin. The test for growth traits started at the age of 120-d, and finished at 365-d. Generally, body measurements were taken every month, but there were animals with lost records. In order to smooth data and predict values at ages of 205- and 365-d, the spline analysis was applied. The following growth traits were derived: weights, heights at withers, hearth girth, and chest depth, predicted at 205- and 365-d of age, respectively. Further, average daily gain from 205- do 365-d was calculated. The semen collection started at approximately 11 months of age. The records included semen volume and concentration. Variance and covariance components and associated heritabilities were estimated by REML from a set of single-trait animal models. Fixed effects were defined as birth year and season, and animal effect was defined as random effect. The heritability estimates for growth traits ranged from .14 to .38. Heritability estimate for semen concentration was moderate (.26). Thus, the improvement of concentration, or at least not negative genetic trend, can be expected even if only phenotypic selection is practiced. This cannot be said for semen volume, as heritability estimate in the present study was low (.04). In this study no clear genetic trend for semen nor growth traits were detected.

Cattle; Semen; Growth; Heritability; Genetic trend

Published by University of Zagreb, Faculty of Agriculture, Zagreb, CROATIA
Sponsored by Ministry Science and Education of the Republic of Croatia