FERTILITY-ASSOCIATED PROTEINS IN HOLSTEIN BULL SEMINAL PLASMA

This study was undertaken to determine whether bovine seminal plasma c ontained protein markers associated with bull fertility, and whether t hese markers were of value in predicting bull fertility. Seminal Plasm a was obtained from 35 Holstein bulls of known fertility. Two-dimensio nal PAGE of seminal plasma samples indicated that two proteins (26 kDa , pl 6.2; 55 kDa, pI 4.5) predominated in higher-fertility bulls, and two proteins (16 kDa, pI 4.1; 16 kDa, pI 6.7) predominated in lower-fe rtility bulls Densitometry data for these proteins in individual sampl es were combined for bulls grouped by fertility level. Average density of the 26-kDa protein was significantly greater in seminal plasma of high-fertility bulls, and high-fertility seminal plasma also contained more of the 55-kDa protein than that of average- and below average-fe rtility bulls. Below average- and low-fertility bull seminal plasma ha d significantly more of both 16-kDa proteins than that of average- and high-fertility bulls. A regression model was developed to predict bul l fertility using the four fertility-associated protein densities. A p lot of actual bull fertility versus that calculated by this model was linear and positively correlated (r = 0.89). These findings indicate t hat bull seminal plasma contains fertility-associated proteins that ar e predictive of bull fertility.