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The goal of the Kerr lab's research program is to aid in the breeding or selection of cows with enhanced resistance to mastitis, an inflammatory disease resulting from entry of foreign substances -- usually bacteria -- into the mammary gland. Currently available management tools and strategies are clearly beneficial though not fully effective in preventing severe mastitis. Further, with increasing concern over the development of antibiotic resistance, it is important to evaluate strategies that limit antibiotic use in mastitis prevention programs. Breeding or selecting mastitis-resistant animals offers such a strategy.

Our goal is to develop a system whereby a blood or tissue sample obtained from a young calf can be tested in the laboratory to predict if she will develop into a lactating cow that has the propensity to develop a moderate, yet effective, response to infection or if she is more likely to suffer from an exaggerated, potentially life-threatening inflammatory response. An animals innate response to infection -- the response phenotype -- appears to be quite variable between cows. This likely reflects genetic makeup in combination with environmentally induced epigenetic modifications that can enhance or repress the strength by which individual genes are expressed. The study of epigenetic modifications of gene expression is a rapidly expanding field of science that seeks to explain, in part, the molecular basis for how environmental conditions during an animal's early development contribute to phenotypic variation.

Our approach is to collect skin or blood samples from groups of animals and perform laboratory testing to determine how strongly an individual's cells respond to challenge with mastitis-causing bacteria or bacterial components. The cellular responses are closely monitored through measurement of proteins, or their genes, associated with the inflammatory response. The goal is to more fully understand the animal-to-animal variation in inflammatory response and thus be able to identify critical control points that may be targets for genetic selection or subject to epigenetic modification. The animals in the experimental groups are then ranked by their cellular responses, and sub-groups of high- or low-responder animals are challenged in vivo to examine the relationship between the responses of the cell-based and whole-animal testing. We can then further examine the cells to detect the genetic or epigenetic differences responsible for the diverse phenotypes.

Future applications of our research are three-fold. First, specific gene polymorphisms may be identified that can lead to enhanced genetic selection of sires and dams. Secondly, management strategies, such as nutritional supplementation or immune challenge, can be utilized with pregnant dams or developing young animals to enhance beneficial epigenetic modifications. Finally, testing an animal's phenotype at a young age could lead to selection of those calves that would be ideal candidates for milking-herd replacements or, alternatively, more appropriate for meat production.

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