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Title: Genetic Parameters of Milk ELISA scores for Johne's Disease

item ATTALLA, S - University Of Minnesota
item SEYKORA, A - University Of Minnesota
item Cole, John
item HEINS, B - University Of Minnesota

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2009
Publication Date: 4/1/2010
Citation: Attalla, S.A., Seykora, A.J., Cole, J.B., Heins, B.J. 2010. Genetic Parameters of Milk ELISA scores for Johne's Disease. Journal of Dairy Science. 93(4):1729-1735.

Interpretive Summary: The heritability of the cow’s ability to establish an immune response to Johne’s disease (paratuberculosis) was computed based on antibody detection in DHI milk samples. Heritability estimates ranged from 0.065 to 0.104, indicating that it is possible to compute genetic evaluations for resistance to Johne’s disease. In the absence of genetic evaluations for Johne’s resistance, genetic correlations indicated that the dairy industry’s current practice of selecting for increased Productive Life and Net Merit should result in cows genetically more resistant to Johne’s.

Technical Abstract: The purpose of this study was to estimate genetic parameters of antibody response to Mycobacterium avium subspecies paratuberculosis using routinely collected Minnesota DHI milk ELISA tests. After all edits, 25,009 tests from 21,514 Holstein cows in 282 Johne’s positive herds were available for analysis. The Johne’s test results were analyzed both as a binary trait (positive or negative) and linear as the transformed ELISA optical density (ln(OD)). Significant fixed effects in the model were age at test date, days in milk, and lab negative control. Random effects were herd test date, animal effect and permanent environment effect. ln(OD) increased with age at test day and days in milk. Heritability estimates ranged from 0.065 to 0.104. Maternal heritabilities were relatively low ranging from 0.012 to 0.021. Repeatabilities ranged from 0.377 to 0.438. Correlations between the sire solutions for ln(OD) for 154 bulls with at least 30 daughters in the analysis and their USDA PTA were: milk,-0.084; fat, -0.199; protein, -0.125; somatic cell score, 0.140; daughter pregnancy rate, -0.122; productive life, -0.292; and Net Merit, -0.339. These correlations suggest that selection for productive life or Net Merit also will improve resistance to Johne’s disease.