Genetic parameters of immune response estimated using genetically divergent lines of Holstein-Friesian dairy heifers
Keywords:dairy cattle, immune response, fertility, genetic parameter
To test the hypothesis that immune responses are useful predictors of fertility in New Zealand (NZ) dairy cattle, we estimated genetic parameters for immune response using a small, experimental herd comprised of genetically divergent lines of Holstein-Friesian dairy heifers whose parents were selected for high or low fertility. Pedigree-based animal models fit using ASReml estimated the heritabilities of antibody-mediated immune response at days 14 and 21 (AMIR14 and AMIR21) and cell-mediated immune response (CMIR) as 0.44, 0.47 and 0.11. Genetic correlations between immune response traits varied: 0.67 for AMIR14 and AMIR21; -0.44 for AMIR14 and CMIR; and -0.07 for AMIR21 and CMIR, suggesting complex and time-dependent genetic relationships between the two types of immune responses. We also detected low to moderate genetic correlations between immune response traits and component traits of NZ’s economic selection index, Breeding Worth (BW), which were close to zero for lowly heritable traits like fertility. These data indicate that immune response is unlikely to be a robust predictor trait for lowly heritable BW component traits, but may be a useful selection trait in its own right as consumer preferences and regulatory agencies accentuate animal health and welfare.
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