Selection experiments for body composition in mice and rats: A review

Abstract

Selection studies for body composition traits that used mice and rats as a model for livestock have been reviewed. Average realized heritability is higher for fat traits (0.49) than for lean traits (0.37), but there is considerable overlap. Selection for lean weight traits produced positive realized genetic correlations in growth, feed intake, gross feed efficiency and lean body mass, but body fat and protein percentages were not modified significantly at age of selection. Selection for fat percentage caused positive genetic correlations in growth, feed intake, feed efficiency and body fat, a negative response in body protein percentage and no response in lean body mass. An inexpensive and non-invasive method of measuring body composition is needed to improve the technical efficiency of selection. Future research should compare genetic variation in body composition at different ages. Desired gains and restricted selection index methods should be applied to modify body composition and growth. Hormones known to affect body composition and growth may be considered as additional selection criteria. Use of transgenic animals carrying genes coding for growth-promoting hormones, combined with artificial selection, offer additional strategies for changing body composition.