Abstract
BackgroundCattle production is dependent upon fertility because it results in producing offspring to offset production costs. A number of semen attributes are believed to affect fertility and are frequently measured as part of routine breeding soundness exams or semen collection procedures. The objective of this study was to perform a single-step genome-wide association study (ssGWAS) for beef bull semen attributes. Beef bull fertility phenotypes including volume (VOL), concentration (CONC), number of spermatozoa (NSP), initial motility (IMot), post-thaw motility (PTMot), three-hour post-thaw motility (3HRPTMot), percentage of normal spermatozoa (%NORM), primary abnormalities (PRIM), and secondary abnormalities (SEC) were obtained from two artificial insemination (AI) centers. A total of 1819 Angus bulls with 50,624 collection records were used for ssGWAS. A five-generation pedigree was obtained from the American Angus Association and consisted of 6521 sires and 17,136 dams. Genotypes on 1163 bulls were also obtained from the American Angus Association and utilized in ssGWAS.ResultsA multi-trait animal model was used for the estimation of single nucleotide polymorphism (SNP) effects. Significant SNP were those with a -log10P-value threshold greater than 4.0. Volume, CONC, NSP, IMot, PTMot, 3HRPTMot, %NORM, PRIM, and SEC have five, three, six, seven, two, six, six, and two genome-wide significant SNP, respectively.ConclusionsSeveral significant SNP were determined to be near or within quantitative trait loci (QTL) associated with beef bull semen attributes. In addition, genes associated with fertility were found to contain or be near the significant SNP found in the study. The results indicate there are regions of the genome that impact fertility, proving inclusion of genomic information into genetic evaluation should be advantageous for genetic improvement of male fertility traits.
Highlights
Cattle production is dependent upon fertility because it results in producing offspring to offset production costs
While using young breeding stock increases the rate of genetic change, the risk of using these bulls is higher because their expected progeny differences (EPD) accuracies are lower
The objective of this study was to perform a genomewide association study for beef bull semen attributes and to identify quantitative trait loci (QTL) regions and genes likely associated with fertility traits in beef bulls
Summary
Cattle production is dependent upon fertility because it results in producing offspring to offset production costs. Genotypes on 1163 bulls were obtained from the American Angus Association and utilized in ssGWAS. The complexity of fertility may be one reason for the lack information available to beef seedstock producers for making fertility selection decisions. Other reasons may include that fertility data is not currently aggregated by beef breed associations and semen quality data from bull studs is largely proprietary. As genomic testing becomes more affordable and a part of regular management practices for seedstock producers, beef cattle producers become more willing and able to utilize the technology. Utilizing genomic technology in breeding decisions allows cattle producers to more confidently incorporate young, unproven sires into their breeding programs. Beef cattle producers do not currently have a selection tool to confidently choose more fertile bulls, nor are current versions of SNP chips enriched in regions where important variants for male fertility exist because they are largely unstudied and unidentified
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