Evaluation of potential effects and genetic parameters in conformational limb defects in Pura Raza Espanola horses

Abstract

Morphological limbs defects are the most frequent defects in horses. The aim of this study was to establish the prevalence, associated effects and genetic parameters of hock and knee defects in Pura Raza Espanola horses, using two different approaches. In Approach_1, the hock defects ~ analysed were closed, open, convergent and divergent and the knee defects studied were buck, calf, bench and knock. Defects were classified into 3 levels: 0 no defect, 1 slight defect and 2 serious defects. Approach_2, which used a linear scale, in a pair of opposing defects, divided into 5 levels, from 2 to 2, where 0 corresponded to the absence of defects: Lateral view (close d/open) and rear view (convergent/divergent) hock defect, lateral view (buck/calf) and frontal view (bench/knock) knee defect. A total of 43,358 horses, with an average age of 5.07 years, were evaluated, with a prevalence of horses affected ranging from 3.31% (bench) to 74.12% (convergent). Genetic parameters were estimated using a Bayesian procedure with the BLUPF90 software. Heritability in Approach_1, ranged from 0.25 (bench) to 0.42 (divergent) and in Approach_2, from 0.18 (bench/knock) to 0.24 (convergent/divergent). The opposing defects may be related to different genes, and it is therefore better to study them as separate defects and not on the same linear scale. The highest positive genetic correlation was between calf vs knock (0.70). Our results imply that selection against limb defects is possible and would allow us to reduce the genetic risk of the horses’ offspring suffering from them.