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Animal Science Departmental Report 2004-2005 Return to Dairy Cattle articles
Application of Molecular Genetics in Dairy Cattle Production M. Ashwell Issue: The incidence of mastitis, infertility and stillbirths continues to escalate as milk production increases in the U.S. Holstein population. It is estimated that mastitis costs dairy producers $2 billion each year and infertility is the primary cause of involuntary culling in dairy herds today. These costs have a huge impact on global competitiveness and the sustainability of farmers, dairy processors, and supporting industries, with the costs associated with these conditions increasing each year. What Has Been Done: Application of marker-assisted selection for economically important traits, such as disease resistance and fertility, would give US dairy producers a greater rate of genetic improvement for these traits while continuing improvement in milk production. However, before marker-assisted selection can be implemented, DNA markers linked to the genes affecting these important traits or the genes themselves must first be identified and characterized. Previous studies have shown that bovine chromosome 18 carries gene(s) affecting somatic cell score (an indirect measure of mastitis incidence), pregnancy rate, stillbirth and dystocia. Research to identify this gene or group of genes began this year in which DNA markers were evaluated in a very popular U.S. Holstein bull and his descendants. Study of DNA markers in a large pedigree will improve our ability to refine the location of the gene(s). Preliminary results indicate the existence of at least one gene affecting pregnancy rate in this large Holstein family. Work is ongoing to further refine the location of the gene. Impact: The identification of DNA markers that flank the genes affecting pregnancy rate or identification of the gene(s) directly affecting the trait may help producers overcome the financial impact of infertility, potentially break negative correlations between milk production and health, and improve animal well-being. Funding source: The North Carolina Dairy Foundation |