Genetic variability of semen characteristics in Japanese Black bulls

Semen characteristics were collected from proven sires of Kagoshima prefecture. A total of 18,704 ejaculation records between February 1994 and February 2008 obtained from 118 bulls were used for analysis. Traits analyzed were volume per ejaculate (VOL, ml), sperm concentration (CON, ×108/ml), number of sperm per ejaculate (NUM, ×108) and sperm motility (MOT, %). Variance components were estimated by restricted maximum likelihood procedure under univariate repeatability animal model. Heritabilities were generally low and estimated to be 0.11 for VOL, 0.05 for CON, 0.09 for NUM, and 0.15 for MOT. Despite the low heritabilities, large variations and high accuracies were observed in predicted breeding values of bulls. Breeding values of MOT ranged from -11.6 to 9.0%, and of NUM indicated standard deviation of 7.3×108. These variations can be used to change semen traits genetically.

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