Estimation of genetic parameters for the prevalence of osseous fragments in limb joints of Hanoverian Warmblood horses

Abstract

Genetic parameters were estimated for the prevalence of osseous fragments in distal (DIJ) and proximal interphalangeal (PIJ), fetlock (FJ) and hock joints (HJ) of Hanoverian Warmblood horses by using residual maximum likelihood (REML) with linear animal models. The analyses were based on the results of 10 standardized radiographs of all four limbs of 3725 young riding horses selected for sale at auction. Transformation factors onto the underlying liability scale were verified by a simulation study. The heritability estimates of osseous fragments on the liability scale were in the range of h2 = 0.19-0.60. Further analyses of osseous fragments in FJ and HJ were performed separately in males and females. In both sexes, the heritabilities of osseous fragments in HJ were higher (h2 = 0.41 in males, h2 = 0.25 in females) than those of osseous fragments in FJ (h2 = 0.21 in males, h2 = 0.23 in females). Osseous fragments in the phalangeal joints (DIJ, PIJ, FJ) were genetically correlated moderately positive (r(g) = 0.19-0.41). The genetic correlations between osseous fragments in the phalangeal joints and in HJ were negative (r(g) = -0.27 to -0.67). Particularly, this applied to osseous fragments in FJ in both sexes, to those in front FJ in males and to osseous fragments in front and hind FJ of females (up to r(g) = -1). The heritability of height at withers was estimated at h2 = 0.27-0.28. Genetic correlations between height at withers and osseous fragments in equine limb joints were mostly moderately positive (up to r(g) = 0.75). We conclude from our results that osseous fragments in phalangeal and hock joints are genetically different traits but sex-specific expression of osseous fragments was unlikely.

Genetic correlations between conformation traits and radiographic findings in the limbs of German Warmblood riding horses

“…The heritability estimate for withers height was higher in our data (h 2 = 0.49) than in the literature (h 2 = 0.25−0.36) [5,15]. Heritabilities of prevalences of radiographic findings agreed with those previously estimated in young Warmblood riding horses [35,37,39,40,42].…”

“…However, four of the five considered radiographic findings were analyzed as all-or-none traits, resulting in extreme deviation from normality and prevalence dependent underestimation of heritabilities and residual correlations that had to be accounted for via transformation. Suitability of transformation factors [6,43] had been substantiated previously via simulation [42], but heritabilities of less prevalent traits such as OFH and DAH might be overestimated. Genetic correlation estimates are not affected by transformation properties, but there is no way to correct for possible underestimation of additive genetic correlations between linear and binary traits [8].…”

“…Detailed description of the examination and documentation procedure is given elsewhere [37,[39][40][41][42]. Osseous fragments in fetlock (OFF) and hock joints (OFH), deforming arthropathy in hock joints (DAH), radiographic appearance of the navicular bones (RNB) and distinct radiographic findings in the navicular bones (DNB) were the quantitatively most important radiological traits and were therefore included in this study.…”

“…Heritability and residual correlation estimates of binary traits (OFF, OFH, DAH, DNB) were transformed from the observed scale to the underlying liability scale [6,43]. Efficiency of transformation factors with encountered data structures has been proven previously [42].…”

Refinement of a quantitative gene locus on equine chromosome 16 responsible for osteochondrosis in Hanoverian warmblood horses

“…Specific causes are still unknown but the origin of OC is multifactorial, including genetic factors, growth rate, body size, nutrition, mineral imbalance, endocrinological dysfunction and biomechanical trauma (Jeffcott, 1991;Van Weeren, 2005). The heritability estimates in animal threshold models were in the range from 0.10 to 0.34 for trotters, warmblood and coldblood horses for the prevalence of OC and these estimates corroborate the hereditary disposition to OC (Grøndahl and Dolvik, 1993;Philipsson et al, 1993;KWPN, 1994;Pieramati et al, 2003;Schober, 2003;Stock et al, 2005b;Wittwer et al, 2007a).…”