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Stock, K. F., & Distl, O. (2005). Prediction of breeding values for osseous fragments in fetlock and hock joints, deforming arthropathy in hock joints, and pathologic changes in the navicular bones of Hanoverian Warmblood horses. Livestock Production Science, 92(1), 77–94.
Abstract: The results of a standardised radiological examination of 5928 Hanoverian Warmblood horses selected for sale at auction were used to predict relative breeding values (RBV) in the 23,662 horses included in the last four generations of the probands' pedigrees. The distribution of the RBV was investigated in the whole four-generation pedigree, in the probands and in those stallions that contributed at least three offspring to the probands. The RBV of the probands' sires were further compared with the officially published performance-based relative breeding values, i.e., total indices dressage (TID) and jumping (TIJ). The sires' level of dressage indices was considerably higher (mean TID=110) than of the jumping indices (mean TIJ=98). Total indices radiographic findings (TIR) were calculated for the sires with varying weighting given to the individual RBV. In each case, this resulted in a mean TIR of 99. Finally, total indices were derived from TIR and TID and/or TIJ in order to develop different selection schemes for all-purpose breeding and for breeding focused on dressage and show jumping. All breeding values under consideration increased by between 1% and 19% when radiographic findings were weighted with between 30% and 60% complementary to the corresponding performance parameters, and when only sires were selected with above average total indices. At the same time, the prevalences of the radiographic findings investigated here were lowered by up to 10% each. When only one radiographic finding was considered at a time, the maximum attainable response to selection was a 16-23% increase in the relative breeding values and a relative decrease in prevalences of radiographic findings of between 31% and 52%. The results of this study indicate that it is possible in horse breeding to consider simultaneously health and performance traits. Medical data should be included in the prediction of breeding values in order to improve the radiological status of today's riding horses.
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Stock, K. F., & Distl, O. (2005). Evaluation of expected response to selection for orthopedic health and performance traits in Hanoverian Warmblood horses. Am J Vet Res, 66(8), 1371–1379.
Abstract: OBJECTIVE: To determine whether selection schemes accounting for orthopedic health traits were compatible with breeding progress in performance parameters in Hanoverian Warmblood horses. ANIMALS: 5,928 horses. PROCEDURE: Relative breeding values (RBVs) were predicted for osseous fragments in fetlock (metacarpo- and metatarsophalangeal) and tarsal joints, deforming arthropathy in tarsal joints, and pathologic changes in distal sesamoid bones. Selection schemes were developed on the basis of total indices for radiographic findings (TIR), dressage (TID), and jumping (TIJ). Response to selection was traced over 2 generations of horses for dressage and jumping ability and all-purpose breeding. Development of mean RBVs and mean total indices in sires and prevalences of orthopedic health traits in their offspring were used to assess response to selection. RESULTS: Giving equal weight toTIR andTID, TIJ, or a combined index of 60% TID and 40% TIJ, 43% to 53% of paternal grandsires and 70% to 82% of descending sires passed selection. In each case, RBVs and total indices increased by as much as 9% in selected sires, when compared with all sires, and prevalences of orthopedic health traits in offspring of selected sires decreased relatively by as much as 16%. When selection was exclusively based on TID, TIJ, or TID and TIJ, percentages of selected sires were 44% to 66% in the first and 73% to 84% in the second generation and TID and TIJ increased by 9% to 10% and 19% to 23%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with exclusively performance-based selection, percentages of selected sires changed slightly and breeding progress in TID, TIJ, or TID and TIJ was only slightly decreased; however, prevalences of orthopedic health traits decreased in offspring of TIR-selected sires.
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Stock, K. F., Hamann, H., & Distl, O. (2006). Factors associated with the prevalence of osseous fragments in the limb joints of Hanoverian Warmblood horses. Vet J, 171(1), 147–156.
Abstract: Factors associated with the prevalence of osseous fragments (OF) in fetlock and hock joints were investigated in a population of young Hanoverian Warmblood horses selected for sale at auction from 1991 to 1998. The study was based on results of a standardized radiological examination of 3127 horses. The prevalences of OF in the two joints were significantly dependent on the date, type and quality of the auction, the region of origin and on the anticipated suitability of the horses for dressage and/or show-jumping. The probability of finding OF increased with wither-height. Furthermore, there was a significant association of the individual sire with the prevalence of OF in both fetlock and hock joints, and of the maternal grandsire with the prevalence of OF in the hock joints. Consequently, both non-genetic and genetic parameters should be taken into account in order to reduce the prevalence of OF in young Warmblood riding horses.
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