Simulation of marker assisted selection strategies in beef cattle

Marker-assisted selection (MAS) has been presented as a promising tool for animal breeding, but its application in beef cattle is still very limited. The technology is still expensive and the way to combine molecular information with more traditional breeding strategies has not been well defined. In order to evaluate MAS strategies, a simulation study was conducted. A beef cattle herd was simulated, in which selection was practiced to improve weaning weight. Three molecular markers with effect on weaning weight explained 40% of the additive variance. Four strategies were compared: mass selection based on phenotypes, marker-assisted selection, selection with animal model (BLUP) and a combined strategy in which the phenotypes were corrected for the effect of the markers and then analyzed with an animal model. Molecular analysis was performed on a limited number of individuals and genotypes of the rest of the population were inferred by segregation analysis. Marker-based selection was the least effective option. Selection based on animal model and the combined strategy performed better than mass selection. Under the simulated conditions, the combined approach showed a slight advantage over the animal model (3% in years 6-8) that would be of little practical relevance. Still, the feasibility of integrating molecular and quantitative genetic information in a single strategy was confirmed. Further research should evaluate options to optimize both the number of markers and of animals to be genotyped.