A method for detection of disease outbreaks was developed using reproduction records from several countries. The outbreaks detected using statistical approaches were confirmed using clinical signs and available diagnostic tests for PRRS and other diseases. The method was used for a) outbreak detection using phenotypic data, b) genetic parameter estimation during disease and healthy periods using a bivariate approach, and c) genetic parameter estimation for a range of challenges using a random regression approach. Data consisted of 3,518,222 records from 447 farms. There were higher variances due to permanent-environment and service-sire effects during disease phases. The additive genetic variance increased as overall challenge load increased. Heritability was highest at extremes of the challenge and non-challenge phases. Genetic correlations decreased as the contrast in challenge load increased. Results suggest usefulness of random regression approach in selection for disease resistance and tolerance.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Genetics of Trait Complexes: Disease resistance, , 088, 2014
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