Marker genotypes , population admixture , and their association with body weight , height , and relative body mass in U . S . federal bison herds

Elucidating genetic influences on bison growth and body composition is of interest, not only because bison are important for historical, cultural and agricultural reasons, but also because their unusual population history makes them valuable models for finding influential loci in both domestic cattle and humans. We tested for trait loci associated with body weight, height, and bison mass index; BMI while controlling for estimated ancestry to reduce potential confounding effects due to population admixture in 1316 bison sampled from 4 U.S. herds. We used 60 microsatellite markers to model each phenotype as a function of herd, sex, age, marker genotypes, and individual ancestry estimates. Statistical significance for genotype and its interaction with ancestry was evaluated using the adaptive false discovery rate. Of the four herds, two appeared to be admixed and two were non-admixed. Although none of the main effects of the loci were significant, estimated ancestry and its interaction with marker loci were significantly associated with the phenotypes, illustrating the importance of including ancestry in the models and the dependence of genotype-phenotype associations on background ancestry. Individual loci contributed about 2.0% of variation in weight, height, and BMI, which confirms the utility and potential importance of adjusting for population stratification.