Correlations of Unfavorable Movement Characteristics in Warmblood Foals and Mares with Routinely Assessed Conformation and Performance Traits
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Animal (2013), 7:1, pp 11–21 & The Animal Consortium 2012 animal doi:10.1017/S1751731112001322 Correlations of unfavorable movement characteristics in warmblood foals and mares with routinely assessed conformation and performance traits - A.-C. Becker1, K. F. Stock1,2 and O. Distl1 1Institute for Animal Breeding and Genetics, University of Veterinary Medicine Hannover, Buenteweg 17p, 30559 Hanover, Germany; 2Vereinigte Informationssysteme Tierhaltung w.V., Heideweg 1, 27283 Verden, Germany (Received 22 November 2011; Accepted 19 March 2012; First published online 6 July 2012) New movement traits reflecting unfavorable movement characteristics were defined on the basis of detailed movement evaluations (DME) of warmblood foals and mares performed in connection with regular breeding events of the Oldenburg horse breeding societies in 2009 and 2010. DME information was available for 3374 foals and 2844 mares and used for correlation analyses with conformation information on 1987 mares from studbook inspections (SBI) in 2009 and performance information on 2758 mares from mare performance tests (MPT) in 2000 to 2008. Analyses of variance revealed few significant differences between scores for SBI and MPT traits in mares without and with indications of imbalance (IMB) in general or specific findings like irregular tail tone or posture (TTP). SBI scores for general impression and development were significantly lower and MPT scores for trot under rider tended to be higher in IMB-positive mares. Genetic parameters were estimated in linear animal models with residual maximum likelihood. Additive genetic correlations and Pearson correlation coefficients between univariately predicted breeding values indicated unfavorable genetic correlations of IMB and TTP with dressage-related conformation and performance traits. For SBI and MPT traits, we found similarities between the correlation patterns for DME traits in foals and mares. The results implied that breeding of dressage horses may benefit from revision of current movement evaluation and consideration of specific movement characteristics. Keywords: indications of imbalance, mare performance test, studbook inspection, genetic correlation Implications the discipline of riding sport, body control and balanced movement under the rider represent basic requirements for To be successful in riding sport of any discipline, horses have to successful performances, justifying that movement traits be able to move in balance under the rider. Gaits are therefore are integral parts of the routine evaluations for breeding routinely evaluated for breeding purposes. However, the tradi- purposes. For mares intended for breeding use, studbook tionally used subjective scoring system does not allow any inspections (SBI) including evaluations of movement at hand inferences on certain movement characteristics. Information are obligatory. Performance tests of mares including movement from detailed movement evaluations (DME) of foals and mares evaluations under rider are voluntarily, so the proportion of was used to define new movement traits and perform corre- performance-tested broodmares is usually below 50%. Never- lation analyses with routinely assessed conformation and per- theless, moderately high heritabilities and significant positive formance traits. Positive genetic correlations with findings genetic correlations with sport performances make perfor- indicating impaired balance in movement imply that horse mance test data a valuable source of information for routine breeding may benefit from extending DME and using more genetic evaluations of riding horses. In contrast, conformation specific information on gaits. information is available for significantly larger proportions of horses, including foals, but the way and extent of use of Introduction conformation data varies between breeding organizations. In Warmblood breeding primarily aims at producing riding Germany, traits from SBI and foal registrations are not included horses, which are highly competitive in sport. Regardless of in the national genetic evaluation for riding horses. Regardless of the evaluation circumstances, the currently used definitions - E-mail: [email protected] of conformation and performance traits are often very general 11 Becker, Stock and Distl and due to the common subjective scoring system do not allow had shown that specific findings could be grouped by the any statements on specific movement characteristics. Although affected structures or parts of the body and information from the benefits of refined trait definitions and descriptive eva- the two groups of judges, SJ and RJ, could be jointly used. luations have been stressed (Rustin et al., 2009), there are This resulted in a set of three composite traits and one still very few warmblood breeding organizations that have summary trait per age group: irregular tail tone and/or posture accordingly revised their routine scoring systems. (TTP; lower than normal tone of tail muscles and/or any Lacking specificity of gait scoring for breeding purposes deviation from normal straight tail carriage), irregular motion may relate to the fact that certain unfavorable movement pattern in hind legs (HM), irregularity in general motion pattern characteristics that are long known still occur. Hereditary (GM) and IMB (any irregularities of movement, i.e. TTP, HM, influences on impaired coordination in equines have been GM and/or pace in foals, TTP, HM and/or GM in mares). The suggested as early as in the first half of the 20th century prevalences of the binary traits were 3.97% for TTP, 2.31% for (Dimock and Errington, 1939; Dimock, 1950). In a recent study, HM, 1.13% for GM and 6.22% for IMB in the foals, and 4.89% indications of imbalance (IMB) were found in almost equal for TTP, 1.37% for HM, 0.08% for GM and 5.49% for IMB in the proportions of warmblood foals and presumptive warmblood mares. Heritability estimates of 0.08 6 0.03 in the foals and broodmares, and genetic analyses implied relevant genetic 0.04 6 0.02 in the mares were found for TTP, and heritability determination and opportunities to select against unfavorable estimates of 0.12 6 0.04 in the foals and 0.05 6 0.02 in the movement characteristics and forbetterbalanceinmovement mares were found for IMB by Becker et al. (2011b). in juvenile and adult horses (Becker et al., 2011b). However, recommending extension of detailed movement evaluations Conformation and performance data (DME) and introduction of new traits into existing breeding Results of conformation evaluations were available for 1987 programs requires knowledge of correlations with the routinely mares presented for studbook entry of one of the Oldenburg assessed traits: unnecessary increase of the number of traits to breeding societies in 2009. The SBI had either taken place in be recorded can be avoided (closely correlated traits), and connection with mare shows or during on-farm visits or foal interferences of concurrent breeding progress (unfavorable registrations. The age at SBI ranged from 2.6 to 23.2 years, correlations) can be taken into account. with a mean age of 7.03 6 4.64 years. The mares were pre- The aim of this study was to investigate the correlations sented standing and moving in walk and trot while led by a between the new movement traits assessed during DME of handler. Scores on a subjective scale from 1 to 10 were given by warmblood foals and mares and the standard conformation the judges of the breeding societies for conformation of head and performance traits routinely assessed during SBI and (Head), neck (Neck), saddle-bearing area (Sad), front limbs mare performance tests (MPT) in the field. (FLimb), hind limbs (HLimb), frame (Frame), type (Type), general impression and development (Dev), walk (Walk), impetus and elasticity (ImpEl) and correctness of gaits (CorrG). In addition, a Material and methods score for body conformation (Body) was derived from the scores DME for Head, Neck, Sad, FLimb, HLimb and Frame, and a total score Information on DME was available for 3374 foals and 2844 was then calculated from scores for Body, Type, Dev, Walk, mares presented for regular breeding events of the Old- ImpEl and CorrG. enburg breeding societies in 2009 and 2010. During foal Results of MPT were available for 2758 mares that had registrations, foals and mares were evaluated by a special participated in 1-day field tests of mares organized by the judge focusing on unfavorable characteristics of movement Oldenburg horse breeding society from 2000 to 2008. The (SJ; foals and mares) and by the regular judges of the mean age at MPT was 3.38 6 0.61 years, with a proportion breeding societies (RJ). Additional movement data of mares of 97% of 3- and 4-year-old mares. Subjective scores on a were collected during regular mare shows and few on-farm scale from 1 to 10 with intervals of 0.5 were given for the SBI of mares, with the same constellations of judges (SJ, RJ). following traits: Walk during free movement (Walk F), Walk All mares were evaluated in hand, that is, led by a handler, under rider (Walk R), Trot during free movement (Trot F), Trot in walk and trot, and the foals were evaluated moving freely under rider (Trot R), Canter during free movement (Canter F), alongside their dams. The mean age at DME was 2.3 months Canter under rider (Canter R), Rideability and Free jumping in the foals (range: 14 days to 7 months of age; 64% younger (Jumping). Rideability scores were given by test riders, whereas than 3 months of age) and 9.2 years in the mares (range: 3 the judges of the breeding societies were responsible for and 24 years of age; 27% up to 5 years old). DME of foals scoring of gaits and jumping. In addition, the balanced mean of were performed in 97 events, including 8 events with more gait scores achieved without rider and under the own rider than 100 evaluated foals (on average 34.79 6 41.39 eval- was calculated for each of the gaits: Walk F 1 R, Trot F 1 Rand uated foals per event).