Breeding for disease resistance - is it successful?

Abstract

Animal health is important both from the perspective of animal welfare and food quality. Also, healthy animals are a prerequisite for economically successful animal production. Health problems can be classified in infectious diseases, genetic disorders and functional diseases. In each case, different approaches are required for genetic improvement. Breeding for disease resistance is not trivial, due to the low heritability of the respective traits, unfavourable genetic correlations to important production traits, and problems to organise a population-wide recording system efficiently. Experimental studies have shown, that breeding for immune capacity based on quantitative immunological parameters is possible. Traditionally, the Scandinavian countries run efficient recording schemes for health traits and give those traits a high weight in their breeding goals. For mastitis in dairy cattle it is shown, that these activities result in a positive genetic trend for this trait relative to the trend in Germany. Marker-assisted selection against genetic defects in pigs is shown to be potentially very efficient. Compared to selection based on frequencies of defects in a boar's progeny, a marker-based pre selection of young boars is shown to lead to a significant increase in genetic progress. In conclusion, the type of recorded health traits, quality of recording and the relative weight of health traits in the breeding goal are seen as the most critical factors affecting efficiency of selection. New technologies and selection strategies have the potential to speed up the genetic trend towards more healthy animals.