Master of Science (MS)


Animal Science (Animal, Dairy, and Poultry Sciences)

Document Type



The objective of this study was to use fluorescent in situ hybridization (FISH) to determine if a skew in the sex ratio was present at the level of the bovine round spermatid. Paraffin embedded bovine testicular tissue obtained from biopsies were used to perform FISH, and the seminiferous tubules were examined. Our findings show that the skew does exist within the round spermatids. Analysis of variance on X- and Y-chromosome bearing round spermatids as affected by sex, slide, picture set, and tubule was performed. Sex showed that the variation in round spermatid sex ratio differed between slides (P = 0.0001). The interaction of sex by slide were indicated to be non-significant (P = 0.0815). Sex within tubule nested in slide showed a significant deviation in sex ratio (P = 0.0122). Picture set showed no significant difference in counts, confirming that the counts were consistent (P = 0.2096). A closer look at the data also showed a 10 to 30% variation in the number of seminiferous tubules with a significant skew per slide. Most the skew was toward the Y-chromosome, but a significant skew toward the X-chromosome was also seen. This skew toward the X-chromosome showed that the skew could be counteracted or reversed. Meiotic drives have been shown to exist in other species. Meiotic drives are alleles with the ability to increase their probability of being transmitted to the next generation. Although we cannot prove that a meiotic drive exists in bovine, our findings agree with the meiotic drive principle. These drives push the sex ratio of the population in one direction. Modifiers attached to these drives can counteract or reverse the effect of the meiotic drive. Environmental factors such as crowding, brought on by intense group housing could also have an effect on the expression of these drives. Further investigation is necessary to completely understand these skews in sex ratio and what factors may affect it.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

John E. Chandler