Individual Variance Component of Fresh Semen Quality in Bali Cattle (Bos javanicus) Bull

Semen quality is an important factor influencing the success of a cattle breeding program, therefore an effort to continuously evaluate semen quality is needed. Indonesia has Bali cattle; it is indigenous, tropically adapted, robust, and has high fertility. Bali cattle need to be developed into meat producer by selecting best traits from bulls and disseminate their sperm through artificial insemination program. To obtain the desired improvement, semen quality became one of the keys to ensure. This study aimed to determine the factor (s) affecting fresh semen quality of Bali cattle bull. In total, 742 ejaculates were collected from nine bulls in 2016-2017 over a 12-month period. Semen was collected twice a week, followed with semen quality evaluation as semen volume (ml), sperm concentration (x10⁶/ml), sperm motility (%), and pH. A linear model was built to obtain the significant fixed factor of season and/or age affecting sperm quality followed by mixed model procedure including individual bulls as random effect to estimate the variance components. The result showed that season didn't give any effect (p>0.05) in all fresh semen quality observed, while there was a significant effect of age (p<0.05) on volume, sperm concentration and pH. There is no interaction (p>0.05) between season and age in this study. The variance component of individual bulls contributed 71.15, 67.92, 48.22, and 11.76% of the total variance of semen volume, sperm concentration, sperm motility, and pH respectively. This study shows that there is a wide variation of semen quality resulted due to the variation between individual of the Bali cattle bull, which mirroring the diverse of Bali cattle genetic. In bull's selection as semen source, careful selection and the application of genetic standard need to be concerned.