Genetic Basis and Risk Factors for Infectious and Noninfectious Diseases in US Holsteins. I. Estimation of Genetic Parameters for Single Diseases and General Health

Abstract

Health data collected from 1996 to 1999 from 177 herds in Minnesota and Wisconsin were analyzed to establish genetic basis for infectious and noninfectious diseases. Three types of health traits were targeted. First, available infectious conditions were used to iden- tifyanimalsthataresuperiorintheirgeneralimmunity (including innate immunity) for infectious diseases. Generalized immunity may be thought of as a combina- tionofimmuneresponsestoavarietyofimmunesystem challenges. Second, single infectious and noninfectious diseases were analyzed separately. Third, infectious re- productive diseases as one category of related condi- tions, and cystic ovary disease as one category of 3 related noninfectious ovary disorders were studied. Data were analyzed using a threshold model that included herd, calving year, season of calving, and par- ity as cross-classified fixed factors; and sire and cow within sires as random effects. Days at risk and days in milk at the beginning of a record were included by fitting the days as continuous covariates in the model. A heritability value of 0.202 ± 0.083 was estimated for generalized immunity. Heritability values of 0.141 and 0.161 were estimated for uterine infection and mastitis, respectively. Heritability of single noninfectious disor- dersranged from0.087to 0.349.Theamount ofadditive genetic variance recovered in the underlying scale of noninfectious disorders tended to zero when combining multiple conditions. The study supports combining in- fectious diseases into categories of interest but we do not recommend the same approach for noninfectious disorders.