Developing marker-assisted models for evaluating growth traits in Canadian beef cattle genetic improvement

The Igenity® genotyping panel with a total of 233 SNP markers was used to genotype 2749 animals of the Beefbooster breeding stock population. A total of 144 SNP makers were used in conducting the association of the SNP markers and the growth traits based on multiple markers regression using stepwise method. The numbers of SNP markers that significantly (p < 0.05) associated with birth weight (BWT), direct genetic effect of weaning weight (WWT), maternal genetic effect of weaning weight (Milk), yearling weight (YWT), mature weight (MWT), and scrotal circumference (SC) were 139, 135, 12, 89, 129 and 105, respectively. Marker score of each individual was calculated as the linear regression on the number of copies of specific allele of all significant (p < 0.05) SNP markers. Bi-variable analysis of marker scores and phenotypes for all traits were conducted using ASReml Software and the genetic parameters for each trait were estimated. The genetic correlations between phenotype and marker score for BWT, WWT, Milk, YWT, MWT and SC were 0.61 ± 0.08, 0.39 ± 0.10, 0.14 ± 0.03, 0.38 ± 0.04, 0.57 ± 0.09 and 0.54 ± 0.10, respectively. The developed two-trait marker-assisted evaluation (TMAE) model increased the estimation accuracy of the phenotypic EBV of the animal when the genetic correlations between phenotype and marker score were high, even with the current limited genotypic and phenotypic information. The average prediction accuracy of phenotypic EBV for BWT, WWT, Milk, YWT, MWT and SC using TMAE were increased by 0.07, 0.07, 0.001, 0.42, 0.08 and 0.22, respectively.