Conformational Traits of Norwegian Cold-blooded Trotters: Heritability and the Relationship with Performance

Abstract

Four body measurements and 18 (forelimb), 20 (hindlimb) and 35 (hoof) subjectively scored conformation traits were investigated on 508 Norwegian cold-blooded trotters. The heritabilities of the body measurements ranged from 0.27-0.73. Several conformational traits showed heritabilities comparable to those of body measurements, and only six had heritabilities approaching zero. Of four faults of conformation that enhanced the prevalence of arthritis in the carpal joint, only calf knees showed significant heritability, which might justify use of the trait for indirect selection against the disease. Increased height at withers and decreased girth circumference significantly increased performance. Base narrow behind, straight hocks and curby hocks were associated with reduced start status and earnings, while cow hocks negatively affected start status only. Conformation was responsible for 10% of the variation in start status and 12% of the variation in earnings, demonstrating the importance of direct selection on breeding values for racing performance.