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Philipsson, J., Arnason, T., & Bergsten, K. (1990). Alternative selection strategies for performance of the Swedish warmblood horse. Livestock Production Science, 24(3), 273–285.
Abstract: The Swedish riding horse population includes about 6000 broodmares and 150 breeding stallions. The overall breeding goal is to produce riding horses competitive in several disciplines, i.e. dressage as well as showjumping and eventing. The effectiveness of this multi-purpose objective was studied in alternative strategies for selecting stallions and mares as candidate dams for them. The alternative selection strategies for stallions included 1-stage (conformation), 2-stage (conformation and performance test) and 3-stage (conformation, performance test and competition results at advanced levels) selection schemes. The mare selection schemes included the corresponding 1- and 2-stage selection schemes. The results clearly showed the 2-stage selection procedure to be most efficient, especially for stallions. It is important that the intensity in selection after the performance test is kept high. Differences in defining the breeding objective are less important, provided the selection is based on a performance test including both dressage and jumping. According to the results, the development of the Swedish performance testing scheme, in which now only 30% of the tested stallions are selected for breeding, seems justified. In mare selection schemes, performance tests also seem to be justified, especially if jumping ability is to be improved. Differences between field and station tests are only minor and since the volume of testing can be much higher in the field this would allow a much stronger selection and should thus be preferred.
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Huizinga, H. A., & van der Meij, G. J. W. (1989). Estimated parameters of performance in jumping and dressage competition of the Dutch Warmblood horse. Livestock Production Science, 21(4), 333–345.
Abstract: The objective of this study is to estimate several genetic parameters in the Dutch Warmblood riding horse population. The traits involved are performances in jumping and dressage competition. The following parameters are estimated: heritabilities for jumping and dressage; phenotypic and genetic correlations between jumping and dressage; and phenotypic and genetic correlations between performances at different ages. These parameters are estimated by restricted maximum likelihood (REML). Data are from 6899 horses with performances in jumping and 10 408 horses with performances in dressage competition. The horses are sired by 205 and 237 stallions for the two traits, respectively. The progeny range in age from 4 to 8 years old. The performance trait is a cumulatively derived score, that reflects the level of performance in competition. A square root transformation of the score is most appropriate to normalize the data. For estimation of phenotypic and genetic parameters the data is split into two data sets according to the age of the sires (offspring sired by older vs. younger stallions). For estimating correlations between performances at 4, 5 and 6 years of age, performances of the offspring out of previous years are linked to the data. The most unbiased estimates of heritability for jumping and dressage are from data derived from the youngest offspring sired by the younger stallions and are 0.20 and 0.10, respectively. Genetic correlation between jumping and dressage ranges from -0.27 to 0.10. The phenotypic correlation between these traits ranges from 0.15 to 0.26. Phenotypic and genetic correlations between performances at 4, 5 and 6 years average 0.95 and 0.75, respectively. These latter results have important implications for genetic evaluation of breeding candidates in the population.
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Langlois, B., Minkema, D., & Bruns, E. (1983). Genetic problems in horse breeding. Livestock Production Science, 10(1), 69–81.
Abstract: The purpose of this paper is to give a short survey of the present problems concerning the genetic improvement of horse breeds. The evolution of these populations in Europe, characterized by a deep change from production of draught horses towards that of leisure horses, is described and the influence of the demographical parameters on the selection of these horse populations, is discussed. The generation interval represents an important handicap only surmounted in the case of racing breeds where a high selection intensity can be practised since all animals are subjected to performance testing. In the other cases, the farmer usually does not use modern breeding techniques, but uses crosses instead, which lead more easily to visible results. The available selection criteria are also dealt with. A distinction is made between direct estimates evaluating the abilities of the animals in practice and the indirect estimates measuring a character in correlation to previous ones. For the former estimates, a distinction is made between those resulting from competitions (handicap, records or earnings) and those resulting from direct in-station measurements (saddle, jumping, dressage abilities, draught power). For the indirect estimates, often used especially for the selection of mares, the most important analysis is obviously that of the conformation. However, in the future early selection criteria according to more physiological data should be sought and developed. Estimation of the breeding value according to a given ability is thereafter pointed out. There are two situations: “the panmictic case” concerning sport and draught horses and “the non-panmictic case” corresponding to racing horses, which give rise to some problems. The setting up of breeding plans is discussed. Due to the different economic situations and various objectives of horse production, conclusions are drawn about the role played by geneticists in the present development of this sector.
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Bruns, E. (1981). Estimation of the breeding value of stallions from the tournament performance of their offspring. Livestock Production Science, 8(5), 465–473.
Abstract: Data from horse-riding competitions recorded in Germany in 1976 and 1977 have been analysed to estimate genetic parameters for performance traits of riding horses measured in dressage, jumping competitions and trials. The performance traits analysed were logarithmic earnings per start, relative place number, and place value. The results are the following. 1. (1) Heritability and repeatability estimates for performance in dressage shows are 0.2 and 0.4 respectively. Corresponding estimates for performance in jumping competitions are 20% less. No genetic differences are found between stallions for performance in trials.2. (2) A selection index for estimating the breeding value of stallions was constructed by using the repeated performances of their offspring in dressage and jumping shows. For this purpose, performance data for at least ten progeny should be available. The correlation between the breeding values estimated from the dressage and jumping performances of the same stallions was approximately zero.3. (3) Reliable progeny-testing requires that the assumptions of mating stallions at random, selecting progeny randomly, and distributing them equally across environmental effects be fulfilled.4. (4) The genetic use of breeding values of stallions estimated from the performance of their progeny is opposed by the prolongation of the generation interval. This can be partly overcome by sampling young stallions and making use of the test results for young progeny only.
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