Genetic evaluation of semen traits in Friesian bulls raised in Egypt.

A total of 14696 semen records were collected from Friesian bulls, kept at International Livestock Management Training Center belonging to Animal Research Institute, Ministry of Agriculture, Dokki, Cairo. Traits studied were volume, motility, livability and sperm concentrates in other to construct selection indexes by using all combination between different traits of semen to improve semen traits in a herd of Friesian bull cattle. Data were analysed by using four traits repeatability model and includes effects of the following fixed factors: the age of animal at semen collection, the combined effect of the month and year of semen collection, and the number of times semen were collected per month. Semen motility, volume and livability were highly influenced (p < 0.001) by all the fixed factors. Heritability estimates for semen traits were moderate and ranged from 0.29 to 0.33. All phenotypic and genetic correlations between different traits are positive and ranged from 0.09 to 0.67 for phenotypic correlations and from 0.02 to 0.68 for genetic correlations, while permanent environmental correlations ranged from −0.69 to 0.12. Estimated Breeding Values ranged from −0.68 to 0.78 ml for semen volume, from −13.17 to 7.34% for motility, from −259.42 × 10−6 to 239.64 × 10−6 for concentrates and from −6.83 to 6.09% for livability. Eleven selection indexes were calculated, selection Indexes not including livability showed a reduced accuracy. This study demonstrated that selection index (I 3) which includes sperm volume, motility and livability or selection index (I 8) which includes sperm volume and livability are the best and both are recommended for Friesian bulls' selection. • Volume, motility and livability of semen were significantly affected by bulls' age, year-month and number of semen collection. • Low heritability estimates were obtained for semen volume, motility, concentrate and livability in Friesian bulls. • Moderate to high phenotypic and genetic correlations between semen traits were obtained for Friesian bulls. • Selection index (I3) which includes sperm volume, motility and livability or index I8 which includes sperm volume and livability are recommended. [ABSTRACT FROM AUTHOR]