Associations between molecular markers and cattle production traits

The genotypic effect of four RFLP markers on cattle production traits including cow growth traits, cow production traits, cow feed intake and efficiency, calf growth traits, calf feed intake, and carcass traits were evaluated. The markers adapted for the study were two markers from regions of growth-related genes (bST: bovine somatotropin and IGF-1: insulin-like growth factor 1) and the other markers from milk protein genes ($k$-CN: kappa casein and $b$-LG: beta lactoglobulin).; Calf birth weight was associated with calf $b$-LG genotype (P = 0.06), with the heaviest weight for AA genotype calves. Cow $b$-LG locus also had slight tendency of association with calf birth weight (P = 0.12). Dominance gene action from calf $b$-LG locus and additive gene action from cow $b$-LG locus were observed from an allele substitution analysis.; Milk fat concentration was associated with bST locus (P = 0.09). BB genotype cows produced the highest fat concentration, and a dominance effect of the locus on the trait was detected. Milk protein and non-fat solid concentrations were also affected by bST locus (P-values were 0.05 and 0.09, respectively). The bST B allele produced higher protein and non-fat solid concentrations in milk than A allele.; Carcass traits were analyzed in two ways based on (1) constant carcass weight, and (2) constant slaughter age. External fat thickness was significantly associated with the bST locus (p = 0.06) when adjusted for final age. Animals with BB genotype tended to be leanest, and an additive gene action was evident from allele substitution analysis. Yield grade, KPH, and retail cutability were also influenced by bST locus (P-values were 0.07, 0.04, and 0.05, respectively) in age-constant analyses. The highest yield grade was found from AA genotype, and the lowest KPH percentage and the highest retail cutability were observed from BB genotype of the bST locus.; Calf $b$-LG locus was associated with rib-eye area (P = 0.03), marbling score (P = 0.08), yield grade (P = 0.05), KPH (P = 0.06), and retail cutability (P = 0.06) when the traits were adjusted for carcass weight. The A allele was related with larger rib-eye area and higher retail cutability than the B allele. The B allele was associated with increased marbling (P = 0.08), yield grade (P = 0.05), and KPH (P = 0.06), and additive gene action was indicated.; In conclusion, possibility of detecting QTLs or linked QTLs through evaluated candidate markers was obvious among some traits, and further studies might facilitate application of genetic marker based animal selection in an animal breeding system. (Abstract shortened by UMI.)...