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

Lina Jönsson Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.

Search for other papers by Lina Jönsson in
Current site
Google Scholar
PubMed
Close
 PhD
,
Agneta Egenvall Department of Animal Breeding and Genetics, Clinical Sciences, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.

Search for other papers by Agneta Egenvall in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
,
Lars Roepstorff Department of Animal Breeding and Genetics, Equine Studies, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.

Search for other papers by Lars Roepstorff in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
,
Anna Näsholm Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.

Search for other papers by Anna Näsholm in
Current site
Google Scholar
PubMed
Close
 PhD
,
Göran Dalin Department of Animal Breeding and Genetics, Equine Studies, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.

Search for other papers by Göran Dalin in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
, and
Jan Philipsson Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.

Search for other papers by Jan Philipsson in
Current site
Google Scholar
PubMed
Close
 PhD

Click on author name to view affiliation information

Abstract

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.

Abstract

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.

Materials and Methods

Case selection—Horses with SWB documentation on health, conformation, and mean scores for gaits and jumping obtained by use of an RHQT performed at 4 to 5 years of age between 1983 and 2005 were included in the study.

Medical and performance records review—A population of 8,238 SWB horses was studied; however, data from 1985 to 1987 were lost and hence not available. Longevity was measured as years in competition, and lifetime performance was measured as accumulated points from placings (ie, upgrading points); both came from official competition statistics. To participate in the RHQT, horse owners consented to have the results used in research. The RHQT was designed to apply to all riding horses, regardless of talent for performance, and no prior qualifications were required. Test locations were distributed throughout Sweden. Horses at an RHQT event (combination of location and date) were examined by experienced, independent judges for health, conformation, and talent for performance. The identity of each horse was confirmed in the SWB pedigree database; there were 8,238 horses with complete health and identity information examined at 187 events, with each event including 10 to 125 horses. The majority of horses (7,750) were 4 years old; 488 were 5-year-old broodmares. Data were obtained from 3,852 mares and 4,386 males (mostly geldings), representing 602 sires with 1 to 189 offspring each. The pedigree data included ancestors of tested horses in 5 generations, comprising 29,693 horses. Mean numbers of offspring examined were 13.7 for stallions and 1.4 for mares. Some horses did not complete the entire RHQT; thus, 8,196 horses had information for conformation, 8,166 for evaluation of gaits, and 8,144 for jumping scores.

Health information—Horses were examined for the same health traits according to a standard protocol.7 Briefly, 2 health inspections of all horses at an event were performed in the same environment, under the same conditions, by the same 2 veterinarians. The first health inspection included a medical health examination and a hoof examination, including 11 traits of hoof shape and hoof wall quality, scored from 0 (not affected) to 3 (severely affected), and the sum (HHS), representing the number and severity of clinical findings, was calculated. The second health inspection included a palpatory orthopedic health examination and a locomotion examination. The palpatory orthopedic health examination included recording and evaluation of effusion, swelling, soreness, and heat or stiffness or atrophy in separate anatomic locations of each limb, including 324 traits scored 0 to 3, and the sum (POHS) was calculated. The locomotion examination evaluated initial movements at a walk, at a trot, and at a trot after a flexion test for each limb, including 12 traits scored from 0 to 3, and the sum (LHS) was calculated. Horses with a flexion test score corresponding to 1, 2, or 3 on the 0 to 3 scale of severity were considered to have had a flexion test reaction. An overall assessment score for both health examinations on a scale between 1 (very poor) and 10 (excellent) was given by the examining veterinarian. For the second health examination, which included the palpatory orthopedic health examination and locomotion examination, this was the H2.

Conformation and talent for performance—Conformation was judged on 5 areas of assessment (body type; head, neck, and body conformation; limb conformation; and walk and trot at hand) on the basis of 11 to 27 specific traits, judged absent or present.6 Overall scores for each area of examination were given between 1 (very poor) and 10 (excellent). Height at withers (most dorsal aspect of the shoulders between the scapulae) from the ground and circumference of cannon (metacarpal) bones (just below the carpus) were also measured.

Talent for dressage and jumping was evaluated for each horse at the RHQT.18 To determine dressage talent, gaits at a walk, trot, and canter under rider and rideability were scored between 1 (very poor) and 10 (excellent). Jumping talent was evaluated as jumping technique and jumping temperament. From these scores, a mean score was constructed for gaits and jumping.

Competition traits—Recordings of results (placings) at regional and national competitions were used to document competition activity of 8,238 horses born between 1979 and 2001. For a few years, starting horses that did not have a placing were recorded as having competed. Horses without a placing in competitions were kept in the study but given a zero value for competition result. Competition results were included from 1983 to 2012. A horse received a placing if it was among the first 20% of horses in a single competition, where upgrading points were given on the basis of rank of placing and level of competition; usually, horses start in several competitions annually. Among all registered SWB horses born between 1979 and 2001, 31% had competition recordings, compared with 58% of RHQT horses. Of 8,238 studied horses, 38% competed in jumping, 28% in dressage, and 5% in eventing; overall, 13% competed in > 1 discipline. Years in competition was used as a measure of longevity, and lifetime performance was used as a measure of lifetime success in competition, which was based on the upgrading points obtained in competitions. Among studied horses, 51% had ≥ 1 upgrading point. Descriptive statistics for longevity and lifetime performance in different categories of studied horses were summarized (Table 1).

Table 1—

Longevity (years in competition) and lifetime performance (accumulated points for placings in competition) in Swedish Warmblood riding horses of various categories evaluated between 1983 and 2005.

 LongevityLifetime performance
CategoryNo. of horsesMedianRangeNo. of horsesMedianRange
All examined horses8,23810–198,23820–8,530
Competing horses4,74631–194,215241–8,530
Show jumping*3,10141–192,714271–8,530
Dressage*2,29031–191,894252–3,551
Eventing*40141–19217222–1,468

Horses could have results in > 1 of these disciplines.

Statistical analysis—Analyses were performed with general linear models in statistical software.b Distributions of longevity and lifetime performance values were not normally distributed (ie, skewed to the right) and were log-transformed as log(x + 1) owing to inclusion of observations with zero values.19 Box-Cox transformation of the data confirmed log-transformation as most appropriate; other traits were kept untransformed as in previous studies.5–7 Sex and event were associated with RHQT results and thus were included in the statistical model.5–7 Further analysis revealed that sex (including number of registered offspring of mares; P < 0.001), event (P < 0.05), and birth year (P < 0.05) were associated with longevity and lifetime performance. Results of the RHQT between horses with and without registered competition activity later in life was estimated as a fixed effect by use of the following model (model 1):

article image

where RHQT is each RHQT score analyzed individually; μ is the population mean; sex is the fixed effect of sex of the horse (male or female); event is a fixed effect representing the combined effect of place, year, and judge; competition status is the fixed effect of absence (0) or presence (1) of registered competition activity; and e is an error term. Subscripts are indexes representing particular observations. Horses with no competition results had lower talent, health, and conformation scores, except for limb conformation, than horses with competition results (Table 2); therefore, all studied horses with RHQT examinations were included in further analyses regardless of competition status in which horses without competition records obtained a zero for longevity and lifetime performance. Results were determined in absolute units as well as in SD units, to compare estimated associations with each RHQT trait with variances of different magnitudes. Further, of the 2.4% horses that did not complete the entire RHQT, predominantly owing to health problems, only one-third (0.8%) had competition records later in life, which was considerably less than the typical RHQT horse. Thus, it was considered necessary to include all RHQT horses that had a complete health examination in the study, regardless of whether they completed the entire RHQT or not.

Table 2—

Mean ± SD scores for health, conformation, gait, and jumping talent variables in Swedish riding horses evaluated by use of an RHQT.

   Estimated difference between noncompeting and competing horses* 
VariableNo. of horsesMean ± SDAbsolute unitsSD unitsPvalue
Health status     
H28,2388.79 ± 1.37−0.18−0.13< 0.001
LHS8,2120.42 ± 1.070.130.12< 0.001
POHS8,2383.21 ± 3.650.260.07< 0.001
HHS8,2380.65 ± 0.930.050.05< 0.01
Conformation     
Type8,1967.82 ± 0.59−0.09−0.15< 0.001
Head, neck, and body8,1967.73 ± 0.56−0.03−0.05< 0.05
Limb8,1967.35 ± 0.66−0.02−0.03NS
Walk at hand8,1967.38 ± 0.76−0.08−0.11< 0.001
Trot at hand8,1967.11 ± 0.80−0.13−0.16< 0.001
Height at withers (most dorsal aspect of the shoulders between the scapulae [cm])8,234164.4 ± 4.37−0.37−0.08< 0.001
Circumference of metacarpus (cm)8,23421.3 ± 0.97−0.39−0.40< 0.05
Gait     
Walk8,1666.69 ± 0.98−0.17−0.17< 0.001
Trot8,1666.33 ± 1.00−0.20−0.20< 0.001
Canter8,1666.70 ± 0.98−0.31−0.32< 0.001
Rideability8,1666.58 ± 0.97−0.28−0.29< 0.001
Overall gait score8,1666.57 ± 0.81−0.24−0.30< 0.001
Jumping     
Technique8,1446.67 ± 1.41−0.56−0.40< 0.001
Temperament8,1446.76 ± 1.55−0.60−0.39< 0.001
Overall jumping score8,1446.71 ± 1.42−0.58−0.41< 0.001

Determined from general linear models of differences in RHQT scores between horses with and without competition results. P values indicate comparison between noncompeting and competing horses.

NS = Not significant.

Associations determined via regression analysis between conformation, health, and talent scores and log-transformed values of longevity and lifetime performance were analyzed with the same approach, including fixed effects of sex and number of registered offspring of mares (P < 0.001), event (P < 0.01), and birth year (P < 0.05), by use of another model (model 2a):

article image

where y is longevity or lifetime performance. The fixed effect of sex included 4 groups: mares with 0 offspring, mares with 1 to 7 offspring, mares with > 7 offspring, and males, for which number of offspring was set to 0. The associations of longevity and lifetime performance with being a mare with each of 1 through 7 offspring were similar; therefore, these mares were grouped together. These mares generally competed for a longer time than mares with 0 offspring, whereas mares with > 7 offspring had the shortest longevity. Males generally competed the most. In addition to the 4 health traits and the 7 conformation traits, the regression effects of 2 talent scores, mean scores for gaits and jumping, were each analyzed. The linearity of the effects of health, conformation, and talent scores on competition traits was tested by including a quadratic term in the model. However, only height at withers and circumference of cannon bones had curvilinear relationships with longevity and lifetime performance. Additionally, the effect of POHS, grouped into type of clinical finding (effusion, swelling, heat, soreness, and stiffness or atrophy) and systemic location (joints, muscles, tendons and suspensory ligaments, skeleton and hoof cartilage) were studied (model 2a).

Specific health traits (with findings scored as 0 [none], 1 [minor], 2 [moderate], or 3 [severe]) and conformation traits (scored 0 [absent] or 1 [present]) were analyzed as fixed effects on longevity and lifetime performance with model 2a. In these analyses, 15 specific health findings with recorded large effects on health or with high prevalence were analyzed.7 These health traits were found in > 2% of examined horses and had an association with H2 of at least −1.5 points, were among the top 10 most common clinical findings in horses with H2 ≤ 5, or were among the top 10 most common clinical findings in horses with flexion test reactions. Health trait findings were analyzed in 3 groups: none, minor, and moderate or severe. All recorded specific conformation traits were analyzed as fixed effects of absent or present. Significant (P < 0.05) conformation effects are presented.

Multiple regression analyses were performed individually for the association between each overall health trait and longevity and lifetime performance, when the effects of the 5 overall conformation scores were also included, in addition to fixed effects of sex, event, and birth year (model 2b):

article image

Partial effects were also estimated when information on all 4 overall health (H2, LHS, POHS and HHS) and all 5 conformation scores (type; head, neck, and body; limb; walk at hand; and trot at hand) were analyzed simultaneously (model 2c):

article image

Effects of 5 categories of clinical POHS findings (effusion, heat, swelling, soreness, and stiffness or atrophy) were also analyzed simultaneously in a multiple regression analysis (model 2d):

article image

The same approach was applied for 4 groups of systemic location (model 2e):

article image

Effects of flexion test reactions on longevity and lifetime performance were studied specifically for effects of the largest reaction, including all limbs. Effects were analyzed separately (model 2a) and by multiple regression analysis, including the 5 overall conformation scores, POHS and HHS (model 2f):

article image

Logistic regression analysis was used to estimate the OR of competing later in life or not (start status) for horses with no, minor, and moderate or severe flexion test reactions, respectively. Odds ratios were estimated separately (model 3a):

article image

Odds ratios were also estimated with the same model, but included information of 5 overall conformation scores, POHS, and HHS (model 3b):

article image

For all comparisons, P < 0.05 was considered significant.

Genetic correlations—Genetic correlations were estimated on the basis of restricted maximum likelihood by use of an average information algorithm.c Analyses met a convergence criterion for the norm vector of < 10−7. For each of longevity and lifetime performance, 2 multitrait analyses were performed. The first analysis included longevity or lifetime performance and health traits (POHS, LHS, HHS, and H2). The second analysis included longevity or lifetime performance and conformation traits (type; head, neck, and body; limbs; walk; trot; height at withers; and circumference of cannon bones). Mean scores of jumping and gaits obtained at the RHQT were included in each multitrait analysis as contributors of information to the heritability estimate of health, conformation, longevity, and lifetime performance through correlations to the talent scores. For RHQT traits, the same model as in phenotypic analyses, with an additional random genetic effect of animal, was used (model 4):

article image

For longevity and lifetime performance, a similar model was used (model 5):

article image

Correlations between the same traits in different analyses were similar (≤ 0.05 unit difference), and thus mean values of produced estimates are presented. Genetic correlations were analyzed between specific health traits with a large effect or high prevalence and all specific conformation traits on the one hand, and longevity and lifetime performance on the other hand. Bivariate analyses were used, with model 4 for RHQT and model 5 for competition traits. Results for traits with a genetic correlation significantly different from 0 with ≥ 1 competition trait are presented. Linear animal models were used in all genetic analyses for consequent data handling and for enabling multitrait correlation estimates between included continuous and categorical variables.

The linearity of the genetic relationships between height at withers and circumference of cannon bones on one hand, and longevity and lifetime performance on the other, was tested by plotting breeding values for the size measurements against the breeding values for competition traits.

Results

Phenotypic effects—Most overall RHQT traits were associated with the presence or absence of future placings in competition (Table 2). Those health and conformation traits with strongest associations, in SD units, were H2, LHS, overall body type and trot scores, and circumference of cannon bones. Dressage and jumping talent scores also had strong associations with placings in competition.

Associations of conformation and health with longevity and lifetime performance—Associations between young horse health status and conformation were significant for longevity and lifetime performance, when analyzed individually (Table 3). Talent scores (in SD units) for performance had the strongest association with longevity and lifetime performance. Most health and conformation traits had highly significant (P < 0.001) associations with longevity and lifetime performance, with an individual importance of 25% to 50% of the strength of associations between RHQT talent scores on longevity. Estimates (in absolute units) suggested that an LHS of 3 to 4 had the same negative association with longevity as did a decrease of 1 point in the talent score for jumping ability. Results from multiple regression analyses (model 2b) revealed that each health trait contributed unique information (not retrievable from the conformation data) regarding associations with longevity and lifetime performance, when overall conformation trait scores were considered simultaneously. When analyzing all overall health and conformation trait scores simultaneously, estimates (in SD units) suggested that body type, walk and trot at hand, H2, HHS, and POHS were most strongly associated with future longevity (model 2c).

Figure 1—
Figure 1—

Association between height at the withers (distance from the ground to the most dorsal aspect of the shoulders between the scapulae) and number of years in competition (NYC) in 4- to 5-year-old horses. Regression estimates were analyzed for effects on log-transformed NYC; data represent back-transformed values.

Citation: Journal of the American Veterinary Medical Association 244, 12; 10.2460/javma.244.12.1449

Figure 2—
Figure 2—

Association between circumference of the metacarpus and NYC in 4- to 5-year-old horses. Regression estimates were analyzed for effects on log-transformed NYC; data represent back-transformed values.

Citation: Journal of the American Veterinary Medical Association 244, 12; 10.2460/javma.244.12.1449

Figure 3—
Figure 3—

Association between height at the withers (distance from the ground to the most dorsal aspect of the shoulders between the scapulae) and lifetime performance (LPERF) score in 4- to 5-year-old horses. Regression estimates were analyzed for effects on log-transformed NYC; data represent back-transformed values.

Citation: Journal of the American Veterinary Medical Association 244, 12; 10.2460/javma.244.12.1449

Figure 4—
Figure 4—

Association between circumference of the metacarpus and LPERF score in 4- to 5-year-old horses. Regression estimates were analyzed for effects on log-transformed NYC; data represent back-transformed values.

Citation: Journal of the American Veterinary Medical Association 244, 12; 10.2460/javma.244.12.1449

Table 3—

Estimated associations between overall health, conformation, and talent scores determined with an RHQT and longevity and lifetime competition performance (jumping, dressage, and eventing) in 8,238 Swedish riding horses.

       Multiple regression effects
 Single regression effects (Each RHQT trait analyzed individually)Each health trait with all conformation traitsAll health traits and all conformation traits
 LongevityLifetime performanceLongevityLifetime performanceLongevityLifetime performance
VariablePer unitPer SDPvaluePer unitPer SDPvaluePer unitPer SDPvaluePer unitPer SDPvaluePer unitPer SDPvaluePer unitPer SDPvalue
Health status                  
H20.140.19< 0.0010.450.62< 0.0010.10.14< 0.0010.310.42< 0.0010.060.08< 0.050.140.19NS
LHS−0.12−0.13< 0.001−0.3−0.32< 0.001−0.09−0.1< 0.001−0.05−0.05< 0.001−0.04−0.04NS−0.11−0.11NS
POHS−0.04−0.15< 0.001−0.11−0.4< 0.001−0.03−0.11< 0.001−0.01−0.05< 0.001−0.02−0.06< 0.05−0.07−0.24< 0.001
HHS−0.08−0.07< 0.01−0.21−0.2< 0.001−0.07−0.07< 0.01−0.07−0.07< 0.01−0.07−0.06< 0.01−0.18−0.17< 0.01
Conformation                  
Type0.330.19< 0.0011.30.77< 0.0010.250.15< 0.0010.790.47< 0.001  
Head, neck, and body0.140.08< 0.010.720.4< 0.001−0.03−0.01NS0.110.06NS
Limb0.080.05< 0.050.280.18< 0.010.040.03NS0.130.09NS
Walk at hand0.210.16< 0.0010.710.54< 0.0010.110.08< 0.0010.320.25< 0.001
Trot at hand0.270.22< 0.0011.150.92< 0.0010.170.14< 0.0010.670.54< 0.001
Talent                  
Overall gait score0.540.44< 0.0012.62.11< 0.001
—Overall jumping score0.390.55< 0.0011.492.12< 0.001

Longevity and lifetime performance data were log-transformed; estimates are back-transformed estimated effects. P values indicate the significance of the association (regarding both estimates in absolute and SD units) with longevity and lifetime performance.

— = Not determined. NS = Not significant.

Height at withers and circumference of cannon bones had similar curvilinear relationships with longevity, with small differences within the optimum intervals of 164 to 171 cm and 21.2 to 23.2 cm, respectively (Figures 1 and 2). Similar relationships were found between the size measurements and lifetime performance data (Figures 3 and 4).

Table 4—

Estimated prevalence and associations between minor and moderate or severe health findings and longevity and lifetime performance in 8,238 Swedish riding horses.

 Prevalence (%)LongevityLifetime performance
VariableMinorModerate or severeMinorPvalueModerate or severePvalueMinorPvalueModerate or severePvalue
Prevalence > 2% and largest effect on overall health (< −1.5) Atrophied hindquarter muscles*3.30.9–0.33< 0.001–0.47< 0.01–0.62< 0.01–0.84< 0.01
Flexion test reaction in trot (forelimbs or hind limbs)15.84.6–0.23< 0.001–0.42< 0.001–0.55< 0.001–0.76< 0.001
Tarsometatarsal or centrodistal1.80.8–0.03NS–0.28NS0.00NS–0.53NS
Atrophied quadriceps muscles1.60.5–0.20NS–0.14NS–0.50NS–0.60NS
Initial movements in trot, hind limbs2.40.3–0.22< 0.001–0.07NS–0.51< 0.0010.05NS
Poor hoof wall quality2.60.2–0.25< 0.05–0.05NS–0.56< 0.05–0.68NS
Sore back muscles or spinous processes2.90.6–0.11NS–0.02NS–0.36NS–0.27NS
Most common findings in horses with low H2 (≤ 5) Effusion, middle to lower part of carpus8.84.4–0.15< 0.05–0.32< 0.001–0.25NS–0.65< 0.001
Effusion, metatarsophalangeal joint12.13.8–0.07NS–0.25< 0.05–0.30< 0.05–0.42NS
Effusion, femoropatellar joint4.24.2–0.13NS–0.12NS–0.29NS–0.51< 0.05
Effusion, tarsocrural joint13.64.3–0.02NS–0.04NS–0.15NS–0.29NS
Effusion, metacarpophalangeal joint7.32.9–0.10NS–0.01NS–0.38< 0.05–0.20NS
Most common findings with flexion test reaction Effusion, hind limb digital flexor tendon sheaths23.63.1–0.03NS–0.33< 0.01–0.12NS–0.60< 0.01
Swelling, proximal portion of metacarpus12.63.4–0.02NS0.03NS–0.12NS0.06NS

Muscles of the croup (topline of the hindquarters) and semimembranosus-semitendinosus group.

Data are for 8,212 horses.

Excludes variables listed previously in this table.

NS = Not significant.

Longevity and lifetime performance data were log-transformed; estimates are back-transformed estimated effects. P values indicate the significance of the association (regarding both estimates in absolute and SD units) with longevity and lifetime performance.

Additionally, some specific health and conformation findings were individually associated with longevity and lifetime performance (Tables 4–6). Regarding health, the largest negative associations were observed for atrophied croup or hamstrings muscles, flexion test reactions, initial hind limb movements in trot, poor hoof wall quality, and effusions in fetlock joints, stifle joint, carpal joints (middle or lower part of carpus), and hind limb digital flexor tendon sheaths. For some variables, an association was detected only for 1 of the 2 analyzed classes of severity. Effusions and stiffness or atrophy had the strongest negative associations (in SD units) with longevity and lifetime performance, as did findings regarding joints and muscles, in separate and multiple regression analyses. Favorable associations between conformation and longevity or lifetime performance were found for a well-proportioned, large horse, with slightly sloping shoulders, well-positioned neck, long croup, and well-developed withers. Regarding walk and trot at hand, ground covering movements, free-shoulder movements, and good rhythm were positively associated with longevity and lifetime performance. Good hind limb energy during trot at hand was also positively associated with longevity and lifetime performance. The most negative associations with longevity and lifetime performance were found for small or heavy horses with short limbs, a deep thorax, and steep sloping shoulders. For walk and trot at hand, stiff hock and shoulder movements, irregular movements, small overreach, and movements close to the ground, predominantly in trot, were negatively associated with longevity and lifetime performance. Two forelimb deviations, toed-in forelimb conformation and narrow at the carpus, were negatively associated with longevity and lifetime performance, whereas toed-out forelimb conformation had a slightly positive association with longevity.

Table 5—

Prevalence and associations between POHS and longevity and lifetime performance in 8,238 Swedish riding horses.

  Single regression effects
  LongevityLifetime performance
Variable     
Clinical finding     
Effusion     
< 0.001Stiff or     
< 0.001atrophied tissues     
Sore     
NSSwelling     
< 0.05Heat     
NSSystemic location     
Joints     
< 0.001Muscles     
< 0.001Skeleton     
NS     
Tendons     

NS = Not significant.

Longevity and lifetime performance data were log-transformed; estimates are back-transformed estimated effects.

The SDs used were as follows: effusion, 1.86; stiff or atrophied tissues, 0.43; sore, 0.33; swelling, 1.15; heat, 0.11; joints, 2.09; muscles, 0.51; skeleton, 0.83; and tendons, 0.26.

Table 6—

Prevalence of specific conformation traits with a significant (P < 0.05) phenotypic association or a significant (P < 0.05) genetic correlation with longevity or lifetime performance in 8,196 horses.

  Single regression effects
Variable     
Body type     
44.2     
Noble     
Large body size     
Short limbs     
Small body size     
Heavy     
Head, neck, and body     
Slightly sloping shoulder     
Well-positioned neck     
Long croup     
Well-developed withers     
Deep thorax     
Steep sloping shoulder     
Forelimb deviations     
Toe-out     
Toe-in     
Narrow at the carpus     
Parallel displaced metacarpi     
Walk at hand     
Free shoulder movements     
Ground covering     
Good rhythm     
Stiff shoulder movements     
Stiff tarsal movements*     
Trot at hand     
Ground covering     
Free shoulder movements     
Good rhythm     
Good hind limb energy and engagement     
Short steps and small overreach     
Stiff tarsal movements     
Movements close to the ground†     
Stiff shoulder movements     
Irregular movements     
Heavy movements     

Data are for 6,176 horses. †Data are for 2,020 horses.

NS = Not significant.

Longevity and lifetime performance were log-transformed; estimates are back-transformed estimated effects.

Flexion test reactions were associated with a lower OR of competing later in life, both among horses with minor (OR, 0.76) and moderate or severe reactions (OR, 0.59), compared with horses without flexion test reactions (OR, 1) if analyzed individually (Table 7; model 3a). The corresponding OR for moderate or severe flexion test reactions from multiple regression analysis including conformation and health traits was 0.71 (model 3b). For horses without flexion test reactions, 59.2% competed later in life, compared with 52.7% of horses with minor flexion test reactions and 47.5% of horses with moderate or severe reactions.

Table 7—

Odds ratios for horses with flexion test reactions to compete later in life, compared with horses without flexion test reactions, and estimated associations between flexion test reactions and longevity and lifetime performance in 8,212 Swedish riding horses.

 Single regression analysesMultiple regression analyses
 Estimated associationOR to competeOR to competeEstimated association
         LongevityLifetime performance
Variable              
Flexion test reaction              
None              
Minor              
Moderate or severe              
Health traits without flexion test              
POHS              
HHS              
Conformation              
Type              
Head, neck, and body              
Limb              
Walk at hand              
Trot at hand              

Results are from Table 3.

— = Not reported. NS = Not significant.

Longevity and lifetime performance data were log-transformed; estimates are back-transformed estimated effects.

Genetic correlations—Impaired health in overall traits (H2, LHS, POHS, and HHS) was moderately correlated with reduced longevity and lifetime performance (rg = 0.3), with comparably low SEs (Table 8). For conformation, high scores for body type; head, neck, and body; trot at hand; and height at withers were generally moderately and positively correlated with higher longevity and lifetime performance (rg = 0.17 to 0.30). Similar but nonsignificant correlations were found between limb conformation, walk at hand, and circumference of cannon bones and longevity and lifetime performance. Talent score for jumping as a 4- to 5-year-old was highly positively correlated with longevity and lifetime performance (rg = 0.82 to 0.84), whereas gait scores were moderately positively correlated with longevity and lifetime performance (rg = 0.31 to 0.38), similar to those for health and conformation. Genetic relationships between height at withers, circumference of cannon bones, and longevity and lifetime performance were linear or near linear.

Table 8—

Genetic correlations and SEs between RHQT recordings of health status, conformation, and talent scores for performance and longevity and lifetime performance in Swedish riding horses.

  LongevityLifetime performance  
RHQT variableNo. of horsesrSErSE  
Health status       
    H28,2380.300.120.350.11  
    LHS8,212−0.310.15−0.360.14  
    POHS8,238−0.260.10−0.260.10  
    HHS8,238−0.280.11−0.310.11  
Conformation       
    Type8,1960.230.080.250.08  
    Head, neck, and body8,1960.260.090.300.08  
    Limb8,1960.210.140.210.14  
    Walk at hand8,1960.140.080.150.08  
    Trot at hand8,1960.240.070.290.07  
    Height at withers8,2340.190.070.170.07  
    Circumference of metacarpus8,2340.130.080.130.07  
Talent (overall)       
    Gaits8,1660.310.070.380.06  
    Jumping8,1440.840.050.820.05  
    Heritability0.200.020.240.03  

— = Not reported.

Longevity and lifetime performance data were log-transformed.

Some specific health and conformation traits were genetically correlated with longevity and lifetime performance (Table 9). Atrophied croup or hamstring muscles, effusions in fetlock and carpal joints, and flexion test reactions were negatively correlated with longevity or lifetime performance (rg = 0.25 to 0.38), as were the sum of effusions and sum of findings in joints. For conformation traits, small horses, parallel displaced cannon bones (sometimes also called offset knees), and stiff movements in walk and trot were negatively correlated with lifetime performance and to some extent longevity. Positive correlations were found between several traits characterizing good movements in trot and lifetime performance (rg = 0.19 to 0.35).

Table 9—

Prevalence, heritability, and significant (P < 0.05) genetic correlations (rg) and SEs between specific health and conformation traits and longevity and lifetime performance in Swedish riding horses.

    LongevityLifetime performance
VariablePrevalence (%)Heritability (observed)     
Clinical finding* (n = 8,238)       
    Atrophied hindquarter muscles4.20.030.01−0.340.17−0.380.17
    Effusion in middle or distal part of carpus13.20.060.02−0.310.12−0.320.12
    Effusion in metacarpophalangeal joint10.20.050.01−0.280.14−0.290.13
    Flexion test reactions (forelimbs or hind limbs)20.50.030.01−0.280.16−0.320.16
    Effusion in metatarsophalangeal joint15.90.060.02−0.260.13−0.260.12
    Sum of clinical findings of effusion55.70.130.02−0.250.10−0.280.10
    Sum of clinical findings in joints60.10.130.02−0.250.10−0.270.10
Conformation (n = 8,196)       
    Type       
    Noble23.70.220.03−0.130.09−0.190.09
    Small body size7.40.100.040.000.14−0.310.10
Limb deviation       
    Parallel displaced metacarpi10.80.070.02−0.330.12−0.310.12
Walk at hand       
    Stiff shoulder movements9.90.060.02−0.260.12−0.260.12
Trot at hand       
    Stiff shoulder movements17.60.110.02−0.290.10−0.350.09
    Ground covering19.90.150.020.120.100.190.09
    Good rhythm59.00.110.020.140.110.250.10
    Heavy movements8.30.110.020.300.110.270.11

Among specific health traits with an observed heritability ≥ 0.03 and with previously determined large association with health or with high prevalence.

Data are for 8,212 horses.

Among all specific conformation traits with a heritability ≥ 0.03.

Longevity and lifetime performance data were log-transformed.

Discussion

The data used for this study were recorded during > 20 years and have thus provided a unique opportunity to explore associations between health and conformation of young horses with longevity and performance. Such a large-scale study, including both specific and overall health and conformation traits in combination with lifetime competition records for > 8,000 horses, we believe, has not been conducted before in riding horses. The RHQT talent and conformation scores are known to be highly valuable sources of information and are currently included in the breeding evaluation of SWB horses.19 Also, specific RHQT traits of health and conformation have substantial heritabilities and are valuable for studies such as the present study.5–7 A mean of 23% of available SWB riding horses participated in the RHQT, of which approximately 50% had detailed health and conformation records available. Horses were fairly unselected for talent because all horses were tested for talent in both disciplines and because most horses were owned by amateurs. Some nonparticipating horses might have been less healthy, which might have led to an underestimation of the genetic and phenotypic variation of health in the population. Clear associations with future longevity, nevertheless, were found.

Longevity, defined as years active in competitions, was considered highly relevant for the SWB breeding goal of producing durable and high-performing competition horses. Because horses may have occasional years of inactivity in their competitive careers, the number of active years in competition was used as a longevity measure, in contrast to the consecutive years from first to last start. Thus, a year of inactivity in competition (eg, because of injury, breeding, or nonavailability of rider) resulted in a 1-year-shorter career for that horse than what would be recorded if the years between the first and last year of competition were used, but no further adjustments were made for the inactivity. Lifetime performance was a measure of success of horses in competitions because it was more related to the quality of the horse than was longevity. Information of years alive was not available and may not coincide with the use of horses for competition (eg, if horses alternatively are used for breeding or leisure riding). Years in competition has also been used in other studies9,10 as a measure of longevity; however, it is not a pure measure of functional longevity because it is influenced by the talent of the horse for 1 or several sport disciplines. Furthermore, registered competition results (both longevity and lifetime performance) mainly represented placings, so horses competing without any placing in any competition in a given year were not included, except for a few of the years. Results must be interpreted with this in mind. The documentation of competition traits was limited to results from Swedish competitions, in which horses competing internationally and exported horses do not have full documentation of their competition careers. Only competition data of studied RHQT horses were used in the analyses. Horses without competition records received a zero value for competition activity, in contrast to studies of Viklund et al19 and Braam et al,10 in which horses without competition records were excluded from analyses. Exclusion of such records might lead to underestimation of the genetic variation in longevity and lifetime performance because competition horses are preselected because of health and performance results. Additional analyses (data not shown) revealed that horses that did not complete the entire RHQT test but only participated in the health examinations (n = 42) often showed lameness and also had fewer competition results later in life: 40% of these horses had ≥ 1 competition record versus 58% of all examined horses, and mean lifetime performance was 24 points, versus 67 points of all examined horses.

Ideally, longevity should have been evaluated for each discipline of the sport (dressage, show jumping, and eventing) to estimate the influence of each health trait on horses used for specific disciplines. However, many horses participate in > 1 discipline and should, therefore, be credited for all competition activities independent of discipline. Lack of competition activity in one discipline may be due to activity in another discipline as a result of talent, rather than because of impaired health. Because show jumping results are most common, longevity and lifetime performance are more influenced by this discipline than by dressage and eventing results. This is demonstrated by the fact that talent scores for jumping had a higher genetic correlation with longevity and lifetime performance (rg > 0.80) than did gait scores in the present study (rg = 0.31 to 0.38). Viklund et al19 found the genetic correlation between gait scores and performance in dressage competitions to be 0.73, which included only horses competing in dressage. Heritabilities were similar between the present and former studies for longevity (0.20 vs 0.1710) and lifetime performance (0.24 vs 0.16 for dressage and 0.27 for show jumping).19 However, the proportion of RHQT horses with placing points from competitions in the present study was slightly higher (58%) than in an earlier study (50%).19

Competition records were included until 2012 when the youngest horses were 11 years old, representing an age when most competition horses have competed extensively and when the best horses have reached the highest level of competition. During the last 5 years of competition results (2008 to 2012), the proportion of studied horses that still competed decreased to 0.2% from 1.0%. Thus, the competition career was over for most horses before 2012. Premature censoring for the youngest horses, therefore, was not considered a source of bias, especially because horses were compared within birth-year classes.

Models used for analyses of RHQT and competition traits included different fixed effects. For competition results, number of offspring was included in the sex effect for mares because of the large interruption in training during pregnancy and foal-rearing, compared with mares without foals and male horses. In addition to the effect of event, birth year was associated with competition results, but not RHQT results. For the event effect, geographic location and year in combination with judge effects were accounted for. Consequently, birth year was also considered because horses of the same age were compared. Changes over time in how competitions are performed were larger than changes over time in the standardized RHQT. Furthermore, the event effect of RHQT contributed additional information on competition results, even if birth year was accounted for. The event effect possibly also accounts for geographic differences in competitions, if many horses stay in the same region throughout life.

Talent scores for performance determined in 4- to 5-year-old horses were associated with longevity and lifetime performance phenotypically. A 1-point higher (better) score corresponded to approximately half a year longer longevity. Moderate genetic correlations were found between the talent score for gaits and longevity and lifetime performance, and high corresponding correlations were found between the talent scores for jumping and longevity and lifetime performance. Due to dependence on health, talent scores were not included as effects in multiple regression analyses. However, mean RHQT performance scores were included in the multitrait genetic analyses to estimate genetic correlations among all traits.

Results consistently revealed that good overall 4- to 5-year-old health status and conformation were associated with increased longevity and better lifetime competition results, both phenotypically and genetically. Genetic correlations between desired conformation and longevity were 0.13 to 0.30, whereas the genetic correlation between good health and longevity was 0.30. This level of genetic correlation between health and longevity was found for H2, POHS, LHS, and HHS. Flexion test reactions were negatively associated with longevity; a moderate or severe reaction corresponded to a 0.4-year shorter longevity. In the POHS category, effusions in the intercarpal and carpometacarpal joints, femoropatellar joint, and fetlock joint were negatively associated with longevity or lifetime performance, supporting a theory of effusions being an early sign of underlying factors negatively affecting health. Depending on the location, effusions may have different degrees of association with longevity. Similar associations between osteochondrosis in the femoropatellar joint or the dorsal aspect of the fetlock joints and decreased activity and success in competition have been found in Belgian show jumping stallions.17 In the present study, atrophied croup or hamstring muscles were negatively associated with longevity and lifetime performance, with a genetic correlation of 0.34 to 0.38 resulting in one-third to half a year shorter competition career. This is a health trait possibly worth greater focus in veterinary examinations. A similar genetic correlation was found for poor hoof wall quality with longevity. The association between moderate or severe initial trot findings (ie, lameness during the trot) and longevity was weak because they were recorded in only 0.3% of horses. It is reasonable to assume that most horses with these severe findings had acute injuries and did not enter the RHQT. Associations with longevity were in particular seen for nonacute clinical findings, such as effusions or stiffness or atrophy, suggesting these clinical findings remain present in each individual for a long period. Effusions generally had a higher heritability (0.14) than other clinical findings (0.00 to 0.06),5 indicating the possibility of improvement through breeding.

Overall conformation was associated with longevity and lifetime performance. Body type; head, neck, and body; trot at hand; and height at withers were found, generally, to be most strongly associated with longevity and lifetime performance. The optimum height at withers found for health in 4- to 5-year-olds was similar to the optimum height found for increased longevity. Results were consistent with a study6 of associations between conformation and 4- to 5-year-old health status, in which intermediate size, well-positioned neck, light forequarters, and correct movements in trot at hand were most strongly associated with health in young horses. Associations were also in accordance with phenotypic results in Standardbred trotters, in which health and conformation were associated with level of performance.a The positive association between slightly sloping shoulders and performance14 was confirmed phenotypically in the present study. In Dutch riding horses, uneven feet were associated with shorter careers in show jumping horses.20 The same study20 found the tallest horses to be at highest risk of culling from basic jumping and dressage, when horses were allocated into quartiles for height at the withers, but found no negative associations for the shortest horses. Few limb deviations were associated with competition results in the present study, which might have been as a result of generally low prevalences of serious limb deviations in the population.

Results of multiple regression analyses indicated that among conformation scores, body type, walk at hand, and trot at hand were most strongly associated with longevity. Head, neck, and body and limb conformations were not associated with longevity or lifetime performance, in multiple regression analyses, because of associations with other conformation scores, in which head-neck-body conformation was strongly associated with body type. The LHS was not associated with longevity when analyzed in combination with other overall health and conformation traits, owing to a strong association with the H2, which was heavily based on locomotion examination findings. Approximately half of the health information on longevity that was not retrievable from the conformation data was influenced by the flexion test results (estimates of LHS and H2). Complementary analyses found horses with flexion test reactions to have lower OR of participating in competitions later in life for minor (0.76) and moderate or severe reactions (0.59). When other veterinary examination results and conformation scores were simultaneously considered, the OR changed to 0.83 for minor and 0.71 for moderate or severe flexion test reactions, and the predicted decrease in longevity was 0.3 years (moderate or severe reactions). This implies that flexion tests provide unique information for prediction of longevity.

The association of health with longevity and lifetime performance indicated that single, minor clinical finding effects were significant but small. The results should be related to the sum of clinical findings of each horse and the fact that longevity had a mean of 2.4 years in competition. An LHS of 3 represented a decrease in longevity of 0.4 years and could represent, for example, 1 minor finding in initial trot and 1 moderate finding in trot after the flexion test, which may or may not be located in the same limb. Compared with the association of talent scores (in SD units) with longevity, health and conformation were highly relevant, commonly accounting for 25% to 50% of the association of RHQT talent scores with longevity. Similar genetic results were found for longevity and lifetime performance because a long competition career generally is necessary to reach the highest level of competition and the most upgrading points. Genetically, upgrading points were slightly more strongly correlated to health and conformation because they possibly provided a more detailed evaluation of competition activity, compared with longevity, which primarily indicated whether a horse placed in a particular year.

The study reported here revealed an association between good health and conformation of young riding horses with their lifetime competition career, measured as longevity and lifetime performance. Results were supported by genetic correlations (rg ≤ 0.3). Scores for body type and movements (especially in trot), hoof status (HHS) and orthopedic health status (POHS, LHS and H2) including results of the flexion test, and talent scores for dressage and jumping were most strongly associated with longevity in competition. Therefore, these traits would be beneficial to include simultaneously in horse breeding programs. Results suggested possibilities to improve health and longevity of riding horses by better management and training of horses and by selection for body type, movements, and health indicators. Such improvements would be beneficial for the overall success in sport because horses would be more likely to avoid lameness. Talent scores of young horse tests have previously been determined to be good early predictors of future performance.18 Young horse health examinations also can contribute important information regarding future longevity and performance, phenotypically and genetically.

ABBREVIATION

H2

Overall orthopedic health score on health examination 2

HHS

Hoof health score

LHS

Locomotion health score

POHS

Palpatory orthopedic health score

RHQT

Riding horse quality test

SWB

Swedish Warmblood studbook

a.

Thafvelin B, Magnusson L-E. Studies on the conformation and related traits of Standardbred trotters. V. Relationships between the conformation and performance of 4-year-old Standardbred trotters. PhD thesis. Swedish University of Agricultural Sciences, Skara, Sweden, 1985.

b.

SAS, version 9.3, SAS Institute Inc, Cary, NC.

c.

DMU, version 6 release 5, Research center Folum, Tjele, Denmark.

References

  • 1. Wallin L, Strandberg E, Philipsson J, et al. Estimates of longevity and causes of culling and death in Swedish warmblood and coldblood horses. Livest Prod Sci 2000; 63: 275289.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Egenvall A, Penell JC, Bonnett BN, et al. Mortality of Swedish horses with complete life insurance between 1997 and 2000: variations with sex, age, breed and diagnosis. Vet Rec 2006; 158: 397406.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3. Sloet van Oldruitenborgh-Oosterbaan MM, Genzel W, van Weeren PR. A pilot study on factors influencing the career of Dutch sport horses. Equine Vet J Suppl 2010;(38):2832.

    • Search Google Scholar
    • Export Citation
  • 4. Egenvall A, Bonnett BN, Olson P, et al. Association between costly veterinary-care events and 5-year survival of Swedish insured warmblooded riding horses. Prev Vet Med 2006; 77: 122136.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Jönsson L, Näsholm A, Roepstorff L, et al. Genetic analysis of clinical findings at health examinations of young Swedish warmblood riding horses. Acta Vet Scand 2013; 55: 22.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. Jönsson L, Roepstorff L, Näsholm A, et al. Conformation traits and their genetic and phenotypic associations with health status in young Swedish warmblood riding horses. Livest Sci 2014; 163: 1225.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7. Jönsson L, Roepstorff L, Egenvall A, et al. Prevalence of clinical findings at examinations of young Swedish warmblood riding horses. Acta Vet Scand 2013; 55: 34.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8. Wallin L, Strandberg E, Philipsson J. Phenotypic relationship between test results of Swedish Warmblood horses as 4-year-olds and longevity. Livest Prod Sci 2001; 68: 97105.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9. Ricard A, Blouin C. Genetic analysis of the longevity of French sport horses in jumping competition. J Anim Sci 2011; 89: 29882994.

  • 10. Braam Å, Näsholm A, Roepstorff L, et al. Genetic variation in durability of Swedish Warmblood horses using competition results. Livest Sci 2011; 142: 181187.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11. Love S, Wyse C, Stirk A, et al. Prevalence, heritability and significance of musculoskeletal conformational traits in Thouroughbred yearlings. Equine Vet J 2006; 38: 597603.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12. Arnason T, Darenius A, Philipsson J. Genetic selection indices for Swedish trotter broodmares. Livest Prod Sci 1982; 8: 557565.

  • 13. Saastamoinen MT, Ojala MJ. Estimates of genetic and phenotypic parameters for racing performance in young trotters. Acta Agr Scand 1991; 41: 427436.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14. Holmström M, Magnusson L-E, Philipsson J. Variation in conformation of Swedish warmblood horses and conformational characteristics of elite sport horses. Equine Vet J 1990; 22: 186193.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15. Koenen EPC, van Veldhuizen AE, Brascamp EW. Genetic parameters of linear scored conformation traits and their relation to dressage and show-jumping performance in the Dutch Warmblood Riding Horse populaion. Livest Prod Sci 1995; 43: 8594.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16. Ricard A, Valette J, Denoix J. Heritability of juvenile osteoarticular lesions of sport horses in France, in Proceedings. 7th World Congr Genetics Appl Livest Prod 2002;S05S08.

    • Search Google Scholar
    • Export Citation
  • 17. Verwilghen DR, Janssens S, Busoni V, et al. Do developmental orthopaedic disorders influence future jumping performances in Warmblood stallions? Equine Vet J 2013; 45: 578581.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18. Viklund Å, Thorén Hellsten E, Näsholm A, et al. Genetic parameters for traits evaluated at the field tests of 3- and 4-year-old Swedish Warmblood horses. Animal 2008; 2: 18321841.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19. Viklund Å, Braam Å, Näsholm A, et al. Genetic variation in competition traits at different ages and time periods and correlations with traits at field tests of 4-year-old Swedish Warmblood horses. Animal 2010; 4: 682691.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20. Ducro BJ, Gorissen B, van Eldik P, et al. Influence of foot conformation on length of competitive life in a Dutch Warmblood population. Equine Vet J 2009; 41: 144148.

    • Crossref
    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 347 0 0
Full Text Views 994 678 285
PDF Downloads 459 242 36
Advertisement