Radiographic findings of juvenile osteochondral conditions detected in 392 foals using a field radiographic protocol.

Radiographic examination in young horses is commonly used to detect juvenile osteochondral conditions (JOCC). The aim of this study is to present the radiographic findings (RF) detected at the age of 6months in the joints of 392 foals from three breeds: French Trotter Standardbreds (FT), Selle-Français Warmbloods (SF) and Thoroughbreds (TB). Radiographic examination included lateromedial views of the fore and hind digits, tarsi and stifles, and dorsopalmar projections of both carpi. In all areas RF indicative of JOCC were classified according to a four-grade severity scoring system. Distribution and severity of the RF varied according to breed with the SF most affected. The most frequently affected site was the hind fetlock (28.3% of foals). The second most affected site was the fore fetlock in TB and SF, while the carpus and proximal tarsus were the second and third affected sites in FT. The radiographic protocol and grading system used can serve as a basis for field research and further studies on the evolution of RF, risk factors for JOCC or the correlation between RF and the subsequent athletic career of horses.

Risk factors for the presence and extent of Developmental Orthopaedic Disease in the limbs of young horses: Insights from a count model.

Developmental Orthopaedic Disease (DOD) in limb joints is frequent, can cause lameness and is a major cause of economic losses for the horse breeding industry. Studies on risk factors for DOD usually dichotomise the outcome to presence/absence without considering the extent of the disease, which can be appreciated by the number or the severity of the lesions. The aim of this study was to assess the effects of growth, exercise conditions and feeding practices on the number of radiographic findings (RF) of DOD in a cohort of horses, assuming that the risk factors associated with the presence of the disease and the number of RF may differ. We recruited broodmares on 21 stud farms in the Normandy region, France in 2002-2004. The stud farms were visited regularly to collect growth, exercise conditions, and feeding practices data from the end of the gestation to the weaning of the foal. The carpus, the front and hind digits, the tarsus and the stifle of the foals were radiographed at approximately six months of age. Each foal was classified according to the absence (no RF) or presence (≥1 RF) of DOD and to the number of RF. A zero-inflated Poisson model was used to simultaneously determine risk factors for presence/absence and for the number of RF of the disease. The convenience sample consisted of 378 foals, 53.1% of which did not have any RF. The mean number of RF per foal was 1.25 and the variance was 2.80. Comparing to the Poisson, negative binomial, and zero-inflated negative binomial regressions, the zero-inflated Poisson model was found to be best suited for these data. Of the 295 foals with complete data, three risk factors were significantly associated with a higher risk of being affected by DOD: high wither height increase, large group size in pasture and large pasture size. Seven risk factors were associated with the number of RF: wither height at 30 days of age, age of the mare, breed, regularity of exercise, Ca/P level in the mare and foal rations, group size in pasture, and the type and frequency of handling. This study shows that risk factors vary for the presence and extent of DOD, and that the use of a count model achieves a more detailed determination of risk factors for the presence of DOD and for the number of RF of DOD compared to the more conventional dichotomy presence/absence of the disease.

Association of growth, feeding practices and exercise conditions with the prevalence of Developmental Orthopaedic Disease in limbs of French foals at weaning.

Developmental Orthopaedic Disease (DOD) in limb joints of horses is frequent and is a common cause of pain and lameness. DOD is a multifactorial disease involving genetics, growth, feeding practices and exercise conditions leading to joint injuries. However, there is no clear understanding of the contribution of each factor. The aim of this cohort study was to assess the adjusted effects of breed and gender, growth, feeding practices and exercise conditions on the prevalence of DOD in the limbs of foals at weaning and on the prevalence restricted to osteochondrosis (OC). Twenty-one farms in Normandy, France, were convenience sampled and enrolled in a cohort study. The study sample consisted of 401 foals from 3 breeds, followed from the 8th month of pregnancy of the mares until weaning period at approximately 6 months of age of the foals. Stud farms were regularly visited to collect growth, feeding practices and exercise conditions data. The carpus, the front and hind digits, the hock and the stifle of the foals were X-rayed at the end of follow-up. Foals were categorised as affected or unaffected by DOD or by OC. Two mixed-effects logistic regression models were used to determine risk factors for DOD or OC, adjusting for clustering by farm. Of the 378 foals with complete data, 47% (95% CI: 42-52) were affected by DOD and 36% (95% CI: 31-41) by OC. Risk was significantly increased for DOD and for OC in Warmblood foals compared to Thoroughbreds (OR 2.8; 95% CI: 1.2-6.5 for DOD, OR 2.9; 95% CI: 1.1-7.5 for OC), in foals with a high wither height at 30 days of age, and in foals with a rapid increase of wither height (for DOD only). Exercise conditions such as large area of pasture, some irregular exercise, or some batch changes were also significant risk factors for DOD or OC. No association was found with quantitative feeding practices; it was likely due to the limited variability of horse regimens and to the partial inclusion of nutritional effects in other factors such as breed and growth. In order to reduce the prevalence of DOD or OC in foals, following the growth and reducing nutritional supply in subjects growing fast, limiting the pasture areas offered and providing a regular exercise to foals seems appropriate. To our knowledge, to date the assessment of adjusted effects of potential risk factors for DOD has never been proposed.

Developmental orthopaedic disease in limbs of foals: between-breed variations in the prevalence, location and severity at weaning.

Developmental orthopaedic disease (DOD) affects all breeds and is a common cause of pain and lameness for horses in sports. A thorough knowledge of between-breed variations for the prevalence of DOD, for its distribution among the various joints and for its severity at earlier stages in the disease process is needed in order to improve the relevance and the cost-effectiveness of DOD screening protocols. However, no prevalence study for DOD simultaneously performed on several breeds with similar farming systems and based on radiographic findings (RF) on quite a large number of joints and views, has been reported earlier. The objective of this study was to describe variations in the prevalence, location and severity of DOD in foals at weaning among Warmbloods (Wb), Standardbreds (St) and Thoroughbreds (Tb) with similar farming systems. DOD assessment was based on RF on the limb joints. A total of 392 foals from 21 volunteer stud farmers were included. To determine the statuses of foals regarding DOD, they were X-rayed on the front- and hind-limb digit, carpus, hock and stifle joints. X-ray data were analysed by three experienced equine veterinarians who gave a common assessment about the entity and the severity of RF. Between-breed variations were analysed in two steps: the first implemented for each anatomical site; the second considered only foals affected by DOD to explore RF association patterns on the affected sites, at foal level. The three breeds were represented by 25.0% of Wb, 41.1% of St and 33.9% of Tb. DOD was present in 66.3% of the foals (95% confidence interval (CI) = 61.6% to 71.0%). Prevalence of foals affected by DOD and distribution of the RF severity score on the anatomical sites differed depending on the breed: Wb foals seemed to be the most affected by DOD. Cluster analyses showed no clear association among sites. However, Wb and Tb foals were preferentially classified together because they were affected on the same sites, whereas St foals were distributed in other classes. The most severely affected sites were the proximal part of the hock and the femoro-patellar joint for Wb and St foals, and the fore fetlock and the distal part of the hock for Tb foals. This is the first epidemiological study reporting between-breed variations in DOD distribution and severity, for the limb joints of foals. These results contribute to broaden the knowledge on DOD and are of great interest to improve detection of DOD within a particular breed.