Morphological variation in the horse: defining complex traits of body size and shape.
Horses, like many domesticated species, have been selected for broad variation in skeletal size. This variation is not only an interesting model of rapid evolutionary change during domestication, but is also directly applicable to the horse industry. Breeders select for complex traits like body size and skeletal conformation to improve marketability, function, soundness and performance in the show ring. Using a well-defined set of 35 measurements, we have identified and quantified skeletal variation in the horse species. We collected measurements from 1215 horses representing 65 breeds of diverse conformation such as the American Miniature, Shetland Pony, Arabian Horse, Thoroughbred, Shire and Clydesdale. Principal components analysis has identified two key dimensions of skeletal variation in the horse. Principal component 1 is positively correlated with every measurement and quantifies overall body size. Principal component 2 captures a pattern of bone widths vs. lengths and thus quantifies variation in overall bone thickness. By defining these complex skeletal traits, we have created a framework for whole genome association studies to identify quantitative trait loci that contribute to this variation.
Department of Animal Science, College of Agriculture and Life Sciences, Cornell University, Ithaca, NY 14853, USA.
S A
SA
Brooks
S
S
Makvandi-Nejad
E
E
Chu
J J
JJ
Allen
C
C
Streeter
E
E
Gu
B
B
McCleery
B A
BA
Murphy
R
R
Bellone
N B
NB
Sutter
D000818:Animals; D049628:Body Size; D001842:Bone and Bones / Q000033:anatomy & histology*; D014644:Genetic Variation; D006736:Horses / Q000033:anatomy & histology* / Q000235:genetics*; D010641:Phenotype