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Abstract

Two-dimensional polyacrylamide gel electrophoresis of seminal plasma samples indicate that two proteins (26 kDa, pI 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 fertility bulls. A regression model was developed to predict bull fertility using the four fertility-associated protein densities. A plot of actual bull fertility versus that calculated by this model was linear and positively correlated (r=0.89). These findings indicate that bull seminal plasma contains fertility-associated proteins which are predictive of bull fertility. Additionally, the ability of seminal plasma to alter the in vitro fertility of ejaculated bull sperm was examined using a sperm penetration assay for zona-free bovine oocytes. Washed, ejaculated sperm from bulls of below (low) or above average (high) fertility were mixed with seminal plasma from the same bull, or with seminal plasma from a bull of contrasting fertility. Washed sperm exposed to seminal plasma from high fertility bulls penetrated more oocytes than when those sperm were mixed with seminal plasma from low fertility bulls (p<0.01). Mixing low fertility sperm with high fertility seminal plasma generally improved penetrating ability compared to low fertility sperm mixed with low fertility seminal plasma.

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