Doctor of Philosophy (PhD)


Dairy Science (Animal, Dairy, and Poultry Sciences)

Document Type



Considerable variation in the percentage of Y-chromosome bearing spermatozoa (%Y-CBS) between ejaculates in the same male has been reported. Collection regime has been speculated to influence the degree of variation in %Y-CBS in bull ejaculates (Chandler et al., 1998). Experiments were designed to evaluate the effects of two collection regimes on %Y-CBS. Conventional PCR combined with gel electrophoresis and image analysis was employed to determine %Y-CBS in ejaculates from two bulls collected on 7-day intervals and two bulls on 21-day intervals. Real-time PCR technology was used to quantify %Y-CBS in the same ejaculates. Boar ejaculates were also analyzed with both techniques and compared to the percent male piglets in litters resulting from the assayed ejaculates. Collection day (P<0.0001) significantly affected %Y-CBS as determined by both PCR methods. Ejaculate nested within bull (P<0.07) was significant in the conventional PCR study and collection frequency (P<0.0001) in the realtime PCR trial. Ejaculate nested within boar was highly significant (P<0.0001) for both technologies. Boar was significant (P<0.002) in the conventional PCR study. Predicted %Y-CBS determined by real-time PCR was significantly correlated (0.52, P=0.004) to percent male piglets. Both PCR techniques were effective in quantifying the variation in %Y-CBS in bull and boar ejaculates. Manipulation of %Y-CBS via collection regime may prove valuable for altering the secondary sex ratio in animal agriculture.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

John E. Chandler



Included in

Dairy Science Commons