Associations of health status and conformation with longevity and lifetime competition performance in young Swedish Warmblood riding horses: 8,238 cases (1983–2005)

• Autores: Lina Jönsson
• Localización: JAVMA: Journal of the American Veterinary Medical Association, ISSN-e 0003-1488, Vol. 244, Nº. 12, 2014, págs. 1449-1461
• Idioma: inglés
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• Resumen

  • Objective—To determine associations of health status and conformation with competition longevity and lifetime performance in young Swedish Warmblood riding horses.

    Design—Cohort study and genetic analysis.

    Animals—8,238 horses.

    Procedures—Horses were examined for health, conformation, and performance from 1983 to 2005, when they were 4 to 5 years old, and competition results from 1983 to 2012 were evaluated. Associations between conformation, health, and talent scores of young horses and longevity (years in competition) and lifetime performance were analyzed. Odds ratios of competing later in life among horses with joint flexion test reactions were determined. Genetic correlations between young horse health, conformation, and talent scores and longevity and lifetime performance were determined.

    Results—Good overall 4- to 5-year-old health, conformation, and talent scores for performance were phenotypically and genetically associated with greater longevity and lifetime performance. Good health was genetically correlated (rg = 0.3) to longevity and lifetime performance. Among conformation traits, body type and movements in the trot were most strongly associated with future longevity; these were genetically correlated (rg = 0.2 to 0.3) to longevity and lifetime performance. Intermediate-sized horses were associated with highest longevity and lifetime performance. Positive flexion test results were associated with lower ORs (OR, 0.59 for moderate to severe and 0.76 for minor reactions) of competing later in life, compared with no reaction, and were associated with lower longevity (0.4 years).

    Conclusions and Clinical Relevance—Horses with good health and conformation at a young age had better longevity in competitions than the mean. Positive correlations suggested that improvement of health and conformation of young horses will enhance their future athletic talent and performance.

    Soundness (ie, absence of lameness) and longevity in riding horses are important traits that affect animal welfare and sport performance and are of economic interest to horse owners. A high proportion (50% to 70%) of culling of riding horses is attributed to musculoskeletal lesions.1–3 Furthermore, costly veterinary care events in riding horses are negatively associated with a 5-year survival rate.4 Therefore, it would be desirable to know the likelihood of a young horse being durable and performing well in the future.

    Previous results from the Swedish RHQT indicate that the health status of young horses varies depending on genetics.5 Other studies6,7 of the same population determined that good health status was associated with desirable conformation. Best health status was found for an intermediate-sized horse, a well-positioned neck, light forequarter conformation, correct movements during the trot, and no major limb deviations (eg, toed-in or toed-out). Whether health status and conformation at a young age influence longevity and whether conformation characteristics that are desirable at a young age increase longevity have remained unknown.

    Studying longevity in horses is difficult because, on a population level, only indirect measures of longevity may be available. In a survey of 1,847 riding horses, Wallin et al1,8 used time from RHQT to death. Risk of early culling was higher for horses with low overall limb scores, whereas the risk was lower for horses with a high total sum of conformation scores. Because of the alternative use of horses for breeding and leisure riding, years in competition, as used by Ricard and Blouin9 and Braam et al,10 may be a useful measurement of functional longevity. Years in competition is genetically associated with talent as a sport horse and age at first competition, with heritabilities of 0.10 to 0.20. In Thoroughbreds, the number of lifetime starts has been used as a measure of longevity, which is negatively affected by conformational limb deviations.11 In Standardbred trotters, heritability of number of lifetime starts was 0.10 in a Swedish study.12 In a Finnish study13 of horses at 3 to 5 years of age, heritability of number of lifetime starts was 0.02 to 0.13.

    Effects of health and conformation traits have also been studied on the basis of different measures of performance. Holmström et al14 studied differences in conformation traits between leisure riding horses and elite horses, which were considered most durable. Slightly sloping shoulders and larger hock angles were more often found in elite dressage and jumping horses, compared with leisure riding horses (n = 61 elite vs 295 leisure horses). In Dutch Warmbloods, a long neck and long, slightly sloping shoulders and croup (the topline of the hindquarters) were also correlated with better performance results in dressage.15 Muscularity of neck and haunches and a slightly sloping croup also were correlated with better overall show jumping performance. No large differences in favorable conformation were found between disciplines. Summed findings of osteochondrosis and isolated findings of osteochondrosis in the stifle (femoropatellar) joint and in the dorsal part of fetlock (metacarpophalangeal or metatarsophalangeal) joints are associated with decreased performance results in show jumpers.16,17 In Standardbred trotters, tall and noble-type horses with normal-sized hoofs, straighter stifle joint and shoulder angles, and no limb deviations performed better than the mean in competitions as 4-year-olds.a Outward-rotated hind limbs, however, were favorable for performance. In conclusion, a few studies of different breeds indicate that there might be some associations between health and conformation with longevity and performance, but the effects of specific health and conformation traits on longevity and performance in riding horses need further investigation. A contributing factor to the limited number of such studies is the lack of large-scale, long-term systematic conformation, health, and performance recordings in horse populations that allow longitudinal studies.

    The aim of the study reported here was to evaluate phenotypic and genetic associations among conformation, health status, and talent scores for performance in young riding horses, with future lifetime performance measured as accumulated points from results (ie, placing) in competitions and longevity measured as years in competition.