Selection Enhanced Estimates of µ-Calpain, Calpastatin, and Dacylglycerol O-Acyltransferase 1 Genetic Effects on Pre-weaning Performance, Carcass Quality Traits, and Residual Variance of Tenderness in Composite MARC III Beef Cattle

Abstract Text: Selection of the composite MARC III population for markers allowed better estimates of effects and inheritance of markers for targeted carcass quality traits (n=254) and nontargeted traits and an evaluation of SNP specific residual variance models for tenderness. Genotypic effects of CAPN1 haplotypes (P=0.12) on LM slice shear force (SSF) were similar in direction and size to previous reports. Effects of divergent CAPN1 haplotypes (1.15 kg) and additive effects of CAST (0.90 kg; P=0.05) on SSF were large. Animals homozygous tender at both markers had 4.11 kg lower SSF than homozygous tough counterparts. The DGAT1 polymorphism affected fat thickness (P=0.02) and VISNIR predicted SSF (P<0.001), with both traits showing additive and dominance inheritance (P<0.05). Genotype specific residual variance models for CAST fit SSF better (P<0.001) than single residual variance models, with tougher genotypes having progressively larger residual (and hence phenotypic) variances.

Keywords: beef tenderness, CAPN1, CAST, DGAT1