| Home | << 1 2 >> |
|
Wallin, L., Strandberg, E., & Philipsson, J. (2003). Genetic correlations between field test results of Swedish Warmblood Riding Horses as 4-year-olds and lifetime performance results in dressage and show jumping. Livestock Production Science, 82(1), 61–71.
Abstract: The main objective of this study was to estimate genetic correlations between traits of young sport horses (4 years old) evaluated in the Swedish Riding Horse Quality Test (RHQT) and later competition results in dressage and show jumping. The data comprised 3708 Warmblood horses born between 1968 and 1982 that had participated in the RHQT as 4-year-olds and 25[punctuation space]605 horses born between 1953 and 1995 with competition records. According to the criteria between 1206 and 1879 horses were common to this two files and were available for the estimations of the genetic correlations. Competition performance traits were cumulative points and cumulative placings received during a horse's lifetime, and a log10 transformation was used to achieve a more normal distribution of the data. Genetic correlations between gait traits scored in the RHQT and competition results in dressage were favourable, in the range 0.63-0.75, and between jumping traits scored in the RHQT and results in show jumping 0.83-0.93. Estimated heritabilities for gait and jumping traits scored in the RHQT were in the range 0.09-0.27 and 0.10-0.18, respectively. Estimated heritabilities for the cumulative points and cumulative placings in dressage and show jumping were 0.17/0.16 and 0.23/0.27, respectively. Thus, the results from the RHQT have proved to be useful for early genetic evaluation and selection of both mares and stallions for sport performance traits.
|
|
Koenen, E. P. C., Aldridge, L. I., & Philipsson, J. (2004). An overview of breeding objectives for warmblood sport horses. Livestock Production Science, 88(1-2), 77–84.
Abstract: The aim of this paper is to review the current breeding objectives of organisations that run a selection programme for warmblood riding horses in the light of an increasing trend in trade of semen across countries. In a questionnaire, 19 horse breeding organisations provided information on breeding objective traits. Variation both in length and amount of details used to define individual breeding objectives was large, reflecting that many traits in sport horse breeding are not easy to measure, and therefore, have to be defined in a subjective way. The majority of the breeding objectives included conformation, gaits and performance in show jumping and dressage. Some breeding objectives also included behaviour, soundness, health and fertility. However, several organisations did not specify the sport discipline and the level of competition (amateur, national or international level) in the breeding objective. In general, relative weightings of the traits within the verbally presented breeding objectives were not given, but were assessed by the organisations in response to this study. The relevance of more information on expected future production circumstances and on the genetic parameters of the traits of interest are discussed. A further review of the consistency, completeness and the number of traits of the present breeding objectives for sport horses is recommended to optimise the efficiency of selection decisions.
Keywords: Breeding objective; Sport horse; Sport performance; Conformation; Specialisation
|
|
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.
|
|
Art, T., & Lekeux, P. (2005). Exercise-induced physiological adjustments to stressful conditions in sports horses. Adaptability of sport horses to stressful conditions, 92(2), 101–111.
Abstract: Among athletic/sports animals, the horse has a unique ability to increase its oxygen uptake by a factor of 60 during heavy exercise. This is achieved by physiological adaptations of all the links in the oxygen chain. Ventilation is increased by a factor of 30. Since the horse is a compulsory nasal breather, this hyperpnea necessitates high transmural pressure changes, which may be responsible for the dynamic collapse of the airways. Blood flow is increased by a factor of 10. Since the left ventricle is not very compliant, this increase necessitates a high filling pressure in the pulmonary circulation, which may induce capillary stress failure and exercise-induced pulmonary haemorrhage. Lastly, oxygen transport is improved by splenic contraction which increases haemoglobinemia by 50%. Sports horses frequently suffer from several problems, which are related either to endogenous or exogenous stresses experienced during their career. These stresses, caused by the use of the horse as a competition animal, may lead to several medical problems. At a systemic level, endogenous stresses include hyperkaliemia, lactacidemia, and hyperthermia; oxidative stress may induce problems at a general, and/or a pulmonary level. External factors, e.g. poor quality of inspired air, transport, hot and humid ambient conditions, and microbiological agents, may also induce abnormal body attacks, and lead to health problems.
|