Genetic relationship between Neck and Limb defects in Pura Raza Española Horses

Neck and limb conformational defects can impair functionality and performance in Pura Raza Española (PRE) horses. However, their potential genetic relationship has not been previously explored.

To estimate the genetic correlations between two types of neck defects (Cresty neck -CN-, Ewe neck -EN-) and twelve conformational limb defects: Forelimb (Buck knee -BUK-, Calf knee -CK-, Bench knee -BEK-, Knock knee -KK-, Splay-footed forelimb -SFF-, Pigeon-toed forelimb -PTF-), rear limb (Closed hock -CH-, Open hock -OH-, Convergent hock -CVH-, Divergent hock -DVH-, Splay-footed rear limb -SFR-, Pigeon-toed rear limb -PTR-). We hypothesized that a genetic relationship exists between neck and limb morphology.

This study analyzed 56,644 PRE horses evaluated between 2012 and 2023. Neck and limb conformation traits were scored using two approaches: A) two-class scale (0-no defect, 1-presence of defect); B) three-class scale for limb defects (0-no defect, 1-slight defect, 2-serious defect) and four-class scale for neck defects (0-no defect, 1-slight defect, 2-serious defect, 3-disqualifying defect). Genetic parameters were estimated, including age as a covariate, and sex, genetic origin, management of breeder's stud farm and inbreeding as fixed effects.

The most frequent limb defect among horses with neck defects was SFR (80.15 % in CN and 72.45 % in EN). Genetic correlations showed moderate relationships, ranging from -0.22(s.d.: 0.090) for EN-SFR to 0.44(s.d.: 0.123) for CN-DVH in approach A, and oscillating from -0.25(s.d.: 0.028) for CNCVH to 0.51(s.d.: 0.228) for CN-SFF in approach B.

Results support the need for integrated selection strategies targeting both anatomical regions.