Reproductive potential and semen attributes in Norwegian Red bulls
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Abstract
With the introduction of genomic selection in cattle breeding, younger bulls without any fertility records have been recruited for semen production. Bull fertility has a major impact on the overall bovine reproductive efficiency. Thus, it is of interest to the cattle breeding industry to have laboratory tests that can predict the fertilization potential of a semen sample. This thesis aimed to study sperm quality traits as well as underlying factors affecting reproductive potential of Norwegian Red bulls. Our results indicated that young bulls are mature enough for their semen to fulfil successful fertilization. However, sperm motility parameters, metabolite contents and semen production efficiency differed between young bulls of 14 and 17 months of age. Even though sperm motility parameters were found to be associated with bull fertility, DFI was the only sperm quality trait with a significant contribution to the model predicting bull fertility. It was demonstrated that conventional sperm quality parameters only partly explain the variation in bull fertility, and that underlying factors affecting fertility might be elucidated by metabolomics and sperm DNA methylation analysis.List of papers
Paper I: Narud, B., A. Khezri, A. Nordborg, G. Klinkenberg, T.T. Zeremichael, E.B. Stenseth, B. Heringstad, E. Kommisrud and F.D. Myromslien. 2020. Semen quality parameters including metabolites, sperm production traits and fertility in young Norwegian Red AI bulls. Manuscript submitted to Livestock Science. To be published. The paper is not available in DUO awaiting publishing. |
Paper II: Khezri, A., B. Narud, E.B. Stenseth, T.T. Zeremichael, F.D. Myromslien, R.C. Wilson, R. Ahmad, and E. Kommisrud. 2020. Sperm DNA Hypomethylation Proximal to Reproduction Pathway Genes in Maturing Elite Norwegian Red Bulls. Front Genet. 11:922. doi: 10.3389/fgene.2020.00922. The article is included in the thesis. Also available at: https://doi.org/10.3389/fgene.2020.00922 |
Paper III: Narud, B., G. Klinkenberg, A. Khezri, T.T. Zeremichael, E.B. Stenseth, A. Nordborg, T.H. Haukaas, J.M. Morrell, B. Heringstad, F.D. Myromslien, and E. Kommisrud. 2020. Differences in sperm functionality and intracellular metabolites in Norwegian Red bulls of contrasting fertility. Theriogenology. 157:24-32. doi: 10.1016/j.theriogenology.2020.07.005. The article is included in the thesis. Also available at: https://doi.org/10.1016/j.theriogenology.2020.07.005 |
Paper IV: Narud, B., A. Khezri, T.T. Zeremichael, E.B. Stenseth, B. Heringstad, A. Johannisson, J.M. Morrell, P. Collas, F.D. Myromslien, and E. Kommisrud. 2020. Sperm chromatin integrity and DNA methylation in Norwegian Red bulls of contrasting fertility. Manuscript. Molecular Reproduction and Development, 1– 88: 187200. doi: 10.1002/mrd.23461. The article is included in the thesis. Also available at: https://doi.org/10.1002/mrd.23461 |