S.A. Attalla,*1,3 A.J. Seykora,1 J.B. Cole,2 and B.J. Heins1
1Department of Animal Science,
University of Minnesota, St. Paul, MN 55108
2Animal Improvement
Programs Laboratory, ARS-USDA, Beltsville, MD 20705
3Cattle
Information System, Faculty of Agriculture, Cairo University, Giza, Egypt Pesca
y Alimentación, Ajuchitlán, Querétaro 76280, Mexico
2009 J. Dairy Sci. (?)
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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.
(Key words: heritability, paratuberculosis, Johne's disease, cattle)