The Veterinary Journal 198 (2013) e75–e80
Contents lists available at ScienceDirect
The Veterinary Journal journal homepage: www.elsevier.com/locate/tvjl
Longitudinal development of equine forelimb conformation from birth to weaning in three different horse breeds C. Robert a,b,⇑, J.-P. Valette a,b, J.-M. Denoix b,c a
Université Paris Est, Ecole Nationale Vétérinaire d’Alfort, USC 957 BPLC, F-94700 Maisons-Alfort, France INRA, USC 957 BPLC, F-94700 Maisons-Alfort, France c Université Paris Est, Ecole Nationale Vétérinaire d’Alfort, CIRALE, F-14430 Goustranville, France b
a r t i c l e
i n f o
Keywords: Equine Conformation Forelimb Breed Growth Foal
a b s t r a c t There is limited published data on conformational changes in the forelimbs of growing foals. This study was designed to describe the changes in conformation of the carpus and distal forelimb from birth to weaning in foals of three different breeds. Evaluation of the conformation of the carpus, fetlock, pastern and foot was carried out in 134 Thoroughbreds, 162 French Trotters and 98 Selle Français (French Warmblood) within 1 month of age and then at approximately 2 month intervals until weaning at approximately 6 months of age. The prevalence of limb deviations decreased from birth to weaning. Angular limb deformities were the predominant conditions in the first month (63.6% of all observed limb deviations) and flexural limb deformities were the most common abnormalities at weaning. The most frequent congenital abnormalities were carpal valgus (42.1% of the foals), fetlock valgus (31.2%), over-at-the-knee (30.8%) and dropped fetlocks (13.0%), with French Trotters and Thoroughbred foals being more affected than Selle Français foals. During the study period, the carpal and fetlock conformation became less valgus. The predominant abnormalities at weaning were fetlock valgus (19.1%), club feet (13.0%) and fetlock varus (11.2%). These observations show that carpal, fetlock and foot conformations changed substantially from birth and weaning. There were significant conformational differences between the three breeds, especially in the first months of life. An understanding of the peculiarities of specific breeds may be useful for the evaluation of individual foal conformation. Ó 2013 Elsevier Ltd. All rights reserved.
Introduction Limb conformation has been considered to be an indicator of performance and orthopaedic health in horses for centuries. Horses are commonly selected on the basis of their conformation, in addition to performance and pedigree (Love et al., 2006; Santschi et al., 2006; Unt et al., 2010). Recent studies on the relationship between conformation and potential injury demonstrated that various clinical conditions were significantly associated with conformation variables (Anderson et al., 2004; Weller et al., 2006c). The assessment of distal limb conformation is part of the daily routine of equine clinicians in the evaluation of lameness and in pre-purchase examinations. Equine practitioners are commonly involved in the evaluation and treatment of conformational deviations in foals (Caron, 1988; Bramlage, 1999). The aims are to submit young horses with the best possible conformation for sale (at weaning or as yearlings) and to optimise conformation for future athletic performance.
⇑ Corresponding author. Tel.: +33 1 43967085. E-mail address: [email protected] (C. Robert). 1090-0233/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tvjl.2013.09.037
Most limb deformities are part of the developmental orthopaedic disease (DOD) complex (O’Donohue et al., 1992). The causes and mechanisms behind these deformities are complex and vary with the clinical entity; however, they are all associated with growth. The first clinical signs appear before 6 months of age and thoracic limbs are most commonly affected (Jeffcott, 2004). Previous studies demonstrated that growth in racehorses is most rapid in the first months of life, whereas in sport-horses it extends over their first years of life (Valette et al., 2008). Significant inter-breed differences in the distribution and severity of radiographic findings of the limb joints in foals at weaning have been recorded (Lepeule et al., 2008). There is extensive information available on variations in conformation in Thoroughbred (TB) horses within populations of mature horses (Mawdsley et al., 1996; Anderson et al., 2004; Weller et al., 2006b; Unt et al., 2010) and yearlings (Love et al., 2006; Santschi et al., 2006). Several studies have also evaluated changes in conformation with growth (O’Donohue et al., 1992; Anderson and McIlwraith, 2004), but very little information is available in Standardbred Trotter and Warmblood horses (Kroekenstoel et al., 2006). Procedures used for the management of limb deformities in foals include exercise and diet modification (Santschi et al., 2006), surgical techniques such as transphyseal bridging or perios-
e76
C. Robert et al. / The Veterinary Journal 198 (2013) e75–e80
teal elevation (Auer, 2011; Baxter, 2011a), and farrier interventions. However, the indications of these techniques remain controversial (Bramlage, 1999; Auer, 2011). Until recently, most foals showing some degree of angular deviation were subjected to surgical correction but a more conservative approach has been advocated in recent years (Auer, 2011; Baxter, 2011a). Conformation assessment is based largely on subjective criteria and empirical evidence (van Weeren and Crevier-Denoix, 2006). Determining whether and when intervention is indicated is difficult (Auer, 2011) in view of the subjective nature of the evaluation and of variations in individual conformation due to posture or muscular fatigue (Hunt et al., 1999). Given the frequency of requests for evaluation and correction of limb conformation in foals, objective background data on the prevalence and the changes in limb deformities associated with age and breed during the first months of life would be of value to practitioners expected to advise breeders and propose an appropriate treatment. The aims of this study were to describe variations in longitudinal development of forelimb conformation in foals from birth to weaning, considering both natural evolution and the impact of human intervention, and to evaluate potential inter-breed differences in conformation and in changes during this period, based on observational data collected in the field from a large sample size. The hypothesis tested was that mild congenital defects may be corrected naturally before weaning, while most moderate to severe congenital defects, or defects acquired after birth, do not completely correct spontaneously. We also tested the repeatability of the use of video for the examination and the longitudinal monitoring of limb deformities in foals. Materials and methods
2006). Deviations of the pastern and hoof were classified as ‘toed out’ or ‘toed in’. Flexural deformities (i.e. in a dorsopalmar plane) included ‘dropped fetlocks’ and ‘calf knee’ (back at the knee) (Love et al., 2006). The terms ‘over-at-the-knee’, ‘upright pastern’ and ‘clubfoot’ were used for hyperflexion of the carpus, fetlock joint and distal interphalangeal joints, respectively. Secondly, an overall score assessing the quality of limb balance was attributed to each forelimb. It reflected the average conformation observed through successive strides. The classification was based upon the dynamic examination alone. The static evaluation was used only to refine the score in case of doubt, for foals that could not be filmed in motion or when the quality of the recording was inadequate to properly evaluate the foal (e.g. foal not walking in a straight line). Grade 0 indicated correct conformation. Grade 1 was used for mild deviations, frequently observed in adult horses and considered to be minor defects or even the far end of biological variation of the normal situation. Nevertheless, although they may not be real (pathological) aberrations, conformations graded 1 were not considered to be normal (grade 0) because of their effect on the joint symmetry and balance, and therefore their potential consequences in the sport or race horse. Grades 2 and 3 (moderate to severe deviation, respectively) indicated the presence of a significant conformation defect. Fig. 1 illustrates the grading system.
Data analysis To evaluate intra-operator repeatability of the conformation evaluation, the films from 100 foals were viewed a second time by the same veterinarians. The various age groups, breeds and full range of anomalies were represented. The agreement on the presence or absence of a limb deformity and on the associated grade (0, 1, 2 or 3) between the first and second evaluations was assessed by calculating the observed percentage agreement (Po) and the kappa coefficient (j), which corrects for chance agreement. The prevalence of each type of limb deviation was calculated for each age group (1 month of age, 2.5 months of age and at weaning) and each breed (FT, SF and TB). The proportions of animals with specific limb deviations and combinations of such defects in the three breeds were compared using the v2 test. To analyse possible differences as a result of development, changes between birth and weaning were analysed using the general linear model (GLM) repeated measurements test. Statistical evaluation was performed with SAS software (SAS Institute), with P < 0.05 considered to be significant. The effects of corrective trimming/shoeing or surgical interventions were evaluated using the v2 test when numbers allowed.
Study population As part of a larger study on juvenile osteochondral conditions (JOCC) (Robert et al., 2013), the growth of 393 foals (202 fillies and 191 colts) born in 21 breeding farms in Normandy, France, was closely monitored. The foals belonged to the three main French breeds and included 134 TB, 162 French Standardbred Trotters (FT) and 98 Selle Français (French Warmbloods, SF). They were kept on pasture for periods ranging from a few hours to 24 h every day, depending on their age and on the practices of the farm. Foals were examined clinically for evidence of skeletal abnormalities at least three times between birth and weaning. Among the 393 foals, 292 were examined during their first month of life, with 72 animals being examined during their first week. All foals were examined again around 2.5 months of age (mean ± standard deviation 73 ± 29 days) and at weaning (172 ± 38 days). At each examination, conformation altering procedures performed, such as corrective shoeing or surgery, were recorded. Foals that had undergone interventions were not excluded from the analysis for purposes of comparison with untreated foals. The study was presented to the Ethics Committee of the Ecole Vétérinaire d’Alfort for approval, but the committee considered that it was not required to give an opinion, since there was no invasive procedure for foals and the only manipulation imposed in the study corresponding to usual interventions on breeding farms.
Results Repeatability of conformation evaluation The overall agreement on the presence or absence of limb deformity was good (Po = 82%; j = 0.61, 95% confidence interval, CI, 0.47–0.75). The same conformation assessment (type of deviation and grade) was made on 145/200 (72.5%) limbs. Among the 55 dissimilar diagnoses, 53 (96.4%) were due to grade 1 limb deformities
A
B
C 2
Conformation abnormalities and grading Any deviation present was recorded and classified. Carpal angular limb deviations (i.e. in a lateromedial plane) included valgus, varus and ‘bench knee’ (offset) (Love et al., 2006; Santschi et al., 2006; Baxter, 2011a). ‘Wind swept’ was used for foals with one leg with carpal valgus and the opposite with carpal varus (Baxter, 2011a). Frontal fetlock deviations were noted as valgus or varus (Santschi et al.,
D
3
Data collection The same veterinarian (CR) conducted all the physical examinations to ensure consistency in the evaluation procedure across all stud farms. The foals were first examined in a static position and then filmed while walking in a straight line on a hard and flat surface in hand, or freely near their dam, depending on farm practices. The video-films were made using a digital video camera (JVC GR-DVP-3) and four views of the foals were taken: front, rear, left side, right side. The films were viewed at a later time by three experienced veterinarians for detection of angular limb deviations (assessed from cranial and caudal views) and flexural deviations (assessed from lateral views).
1
12 3
123
3 12
1 12
3
Fig. 1. Principle of gradation of the most frequent limb deformities in foals. Normal conformation for young foals is schematically represented in black seen from the front view (A and B) and from the right side (C and D). (A) Fetlock valgus. (B) Carpal valgus. (C) Dropped fetlock (in red) and upright conformation (in green). (D) Overat-the-knee. 1, Mild deformity; 2, moderate deformity; 3, severe deformity.
e77
C. Robert et al. / The Veterinary Journal 198 (2013) e75–e80
that were missed (graded 0) at one of the two examination sessions and the last two were a grade 1 carpal valgus noted as carpal varus at the second assessment and a grade 1 fetlock varus noted as fetlock valgus. The agreement on the exact grade (0, 1, 2 or 3) was moderate (Po = 73%; j = 0.56, 95% CI 0.46–0.66). Considering grade 2 and 3 deformities together, the overall agreement on the presence of moderate to severe deviation was good (Po = 92%; j = 0.68, 95% CI 0.54–0.82). Among the 105 limbs where deformities were identified at both evaluations, the overall agreement percentage for the severity was high (Po = 83%) and the agreement was good (j = 0.60, 95% CI 0.43–0.77). In most cases (96.4%), the disagreement in grading was limited to one grade (grade 1 vs. 2 or 2 vs. 3). Prevalence of limb deviations The majority of foals (258/292, 88.4%) examined during their first month were presented with at least one limb deviation graded P1 and 135/258 (52.3%) affected foals had at least one deviation graded 2 or 3. The prevalence and the severity of limb deviations (Table 1) decreased linearly with increasing age (P < 0.01). Most deviations observed at the first examination involved the carpus (185/292, 63.4% of affected foals) or the fetlock (181/292, 62.0% of affected foals). In affected foals, 111/185 (60%) carpal deformities and 88/181 (48.6%) fetlock deformities were considered to be moderate to severe (grade 2 or 3), while 138/185 (74.6%) carpal deformities and 102/181 (56.4%) fetlock deformities were bilateral. At weaning, fetlock deviations (147/393, 37.4%) were more frequent (P < 0.01) than carpal (73/393, 18.6%) or foot deviations (91/ 393, 23.1%), but there were no significant differences in severity; 68/147 (46.3%) fetlock, 31/73 (42.5%) carpal and 33/91 (36.3%) foot deviations were graded 2 or 3. Among the lesions detected at weaning, half of the deviations on the carpus (38/73, 52%) had been observed at the time of first examination; this proportion of congenital deviations was significantly lower in the fetlock (32/ 147, 21.8%) and foot (8/91, 8.8%) (P < 0.05). Irrespective of the joint, 188/257 (73.2%) acquired deviations appeared between 3 months of age and weaning. Angular limb deviations Angular limb deviations were the predominant condition found in the first month of life, representing 288/453 (63.6%) of all observed limb deviations. Carpal valgus and fetlock valgus were the most frequent conditions (Table 2), with 123/292 (42.1%) and 91/ 292 (31.2%) foals affected, respectively. Most carpal valgus deviations (81/123, 65.8%) corrected naturally before 3 months of age and only 22/123 (17.9%) were still present at weaning. Fetlock valgus cases usually corrected spontaneously between 3 and 6 months of age, but 18/91 (19.8%) were still present at weaning. Angular limb deviations were much less frequent at weaning than at birth. Fetlock valgus (75/393, 19.1%), fetlock varus (44/ 393, 11.2%) and carpal valgus (41/393, 10.4%) were the most frequent deviations, half of the cases being graded 2 or 3 (Table 3). A proportion of foals with fetlock valgus (20/75, 26.7%) and varus (9/44, 20.4%) observed at weaning had already been noticed at
the first examination, but many of these conditions (valgus: 24/ 75, 32%; varus: 25/44, 56.8%) were identified for the first time at weaning. However, 24/41 (58.5%) carpal valgus cases noted at weaning were already present at 1 month of age. Eight foals underwent periosteal stripping because of severe carpal valgus at a mean age (± standard error) of 59 (±17) days; in four of these foals, the defect had completely disappeared or had become mild at weaning, whereas in the other four foals the valgus was still present and was grade 2 or 3 at weaning. Two Thoroughbred foals with a grade 2 fetlock valgus at 1 month of age received orthopaedic treatment (splint or medial acrylic hoof extension) and stall rest, which resulted in an improvement of their condition (grade 1 at weaning). Fetlock varus (one graded 3 and two graded 2) was treated in 3/19 affected foals with regular hoof trimming (2 foals) or periosteal elevation (1 foal); none was significantly improved at weaning. Flexural limb deformities Flexural limb deformities were less frequent (165/453, 36.4% of all observed limb deviations) than angular limb deformities at the first examination of the foals. Over-at-the-knee and dropped fetlocks were the more frequent conditions, with 30.8% and 13.0% of the foals affected, respectively (Table 2). Most of these deformities had disappeared at the age of 3 months and only 11/90 (12.2%) and 2/38 (5.3%), respectively, were still present at weaning. Flexural limb deformities were the predominant condition at weaning (369/589, 62.6% of limb deformities). Clubfeet (51/393, 13.0% of foals), followed by over-at-the-knee (28/393, 7.1%) and dropped fetlocks (24/393, 6.1%), were the more frequent conditions (Table 3). Most of these (clubfeet: 36/51, 70.6%; over-atthe-knee: 14/28, 50.0%; dropped fetlocks: 21/24, 87.5%) were first observed at weaning. Two foals with marked digital hyperextension (grade 3) in one or both forelimbs at birth had extended-heel glue-on shoes applied for a few weeks; this resulted in complete recovery in one foal and limited improvement (grade 2) in the other one. Nine foals with clubfoot or upright conformation (grade 2 or 3) at birth received oxytetracycline intravenously once or twice during their first weeks of life. This was combined with stall rest in most cases, and with dorsal hoof extension using acrylic (one foal), foot plate (one foal) and cast (one foal). Except for the last foal, which was also affected by severe hock osteochondrosis, all the defects had disappeared or were considered to be mild at weaning. The evolution tended to be less favourable (P = 0.09) in the 11 untreated foals, with five still affected with grade 2 or 3 defects at weaning. Three foals with acquired club-foot (diagnosed between 2.5 and 6 months of age) were given corrective trimming/shoeing and stall rest; the problem had disappeared at weaning in the youngest foal and improved in the two older ones. Inter-breed variations All anomalies combined, SF had fewer defects than FT and TB, both at birth (P < 0.01) and at weaning (P = 0.04). The proportions of foals with grade 2 or 3 deformities were 27/69 (39.7%) in SF,
Table 1 Prevalence of limb deformities in the forelimbs depending on the age of foals. Age
Number of foals evaluated n
No forelimb deformity n (%)
Moderate (grade 2) to severe (grade 3) forelimb deformity n (%)
0–7 days 8–30 days 1–3 months Weaning
72 230 328 393
5 (6.9) 27 (11.7) 97 (29.6) 159 (40.5)
40 (55.6) 100 (43.5) 103 (31.4) 94 (23.9)
e78
C. Robert et al. / The Veterinary Journal 198 (2013) e75–e80
Table 2 Prevalence of foals showing deviations of the forelimbs at 1 month of age in 292 foals (scored on three occasions) and evolution of this prevalence at 3 and 6 months of age in the same foals. Age Severity Symmetry Foals affected Angular deformities Carpal valgusa,b Carpal valgus NTa,b Carpal varus Bench knee Wind-swepta,b Fetlock valgusa Fetlock valgus NTa Fetlock varusa Fetlock varus NTa Toed-out Toed-inb Flexural deformities Over-at-the-kneea,b Calf knee Uprighta Upright NTa Dropped fetlocka Dropped fetlock NTa Clubfoot Clubfoot NT
3 months
6 months
1–3 Unilateral and bilateral n (%)
1 month 1–3 Bilateral only n (%)
2–3 Unilateral and bilateral n (%)
1–3 Unilateral and bilateral n (%)
1–3 Unilateral and bilateral n (%)
123 (42.1) 115 (39.4) 4 (1.4) 2 (0.7) 28 (9.6) 91 (31.2) 89 (30.5) 37 (12.7) 34 (11.6) 0 3 (1.0)
64 (21.9) 62 (21.2) 0 2 (0.7) 28 (9.6) 28 (9.6) 28 (9.6) 13 (4.5) 12 (4.1) 0 2 (0.7)
77 (26.4) 69 (23.6) 3 (1.0) 2 (0.7) 15 (5.1) 33 (11.3) 31 (10.6) 19 (6.5) 16 (5.5) 0 1 (0.3)
42 (14.4) 34 (11.6) 0 0 18 (6.2) 48 (16.4) 46 (15.8) 16 (5.5) 13 (4.5) 0 1 (0.3)
22 (7.5) 16 (5.5) 0 0 7 (2.4) 18 (6.2) 16 (5.5) 9 (3.1) 6 (2.1) 0 1 (0.3)
90 (30.8) 5 (1.7) 14 (4.8) 8 (2.7) 38 (13.0) 36 (12.3) 18 (6.2) 15 (5.1)
84 (28.8) 5 (1.7) 13 (4.5) 7 (2.4) 36 (12.3) 35 (12.0) 13 (4.5) 13 (4.5)
53 (18.2) 4 (1.4) 6 (2.1) 0 (7.2) 21 (7.2) 19 (6.5) 14 (4.8) 11 (3.8)
25 (8.6) 1 (0.3) 3 (1.0) 0 4 (1.4) 3 1.0) 11 (3.8) 9 (3.1)
11 (3.8) 1 (0.3) 1 (0.3) 0 2 (0.7) 1 (0.3) 9 (3.1) 8 (2.7)
For deviations for which some foals received surgical treatment or corrective trimming/shoeing, data from untreated foals appear on a second line with the annotation NT, not treated. a Significant reduction in the number of congenital deviations between the first month and weaning. b Significant difference in global prevalence between the first month and weaning (corrected congenital deviations not balanced by acquired deviations or vice versa).
Table 3 Prevalence of deviations of the forelimbs of 393 foals at weaning and examination when these were first noted. Age at first detection Prevalence at weaning
First examination
Severity Symmetry
1–3 Unilateral and bilateral
1–3 Bilateral only
2–3 Unilateral and bilateral
Foals affected
3 months
6 months
1–3 Unilateral and bilateral
n (%)
n (%)
n (%)
n (%)
n (%)
n (%)
Angular deformities Carpal valgus Carpal varus Bench knee Wind-swept Fetlock valgus Fetlock varus Toed-out Toed-in
41 (10.4) 2 (0.5) 2 (0.5) 8 (2.0) 75 (19.1) 44 (11.2) 14 (3.6) 34 (8.7)
13 (3.3) 0 2 (0.5) 8 (2.0) 18 (4.6) 13 (3.3) 11 (2.8) 12 (3.1)
23 (5.9) 1 (0.3) 1 (0.3) 3 (0.8) 42 (10.7) 22 (5.6) 2 (0.5) 9 (2.3)
24 (6.1) 0 0 1 (0.3) 20 (5.1) 9 (2.3) 0 1 (0.3)
4 (1.0) 0 0 2 (0.5) 31 (7.9) 10 (2.5) 2 (0.5) 8 (2.0)
13 (3.3) 2 (0.5) 2 (0.5) 5 (1.3) 24 (6.1) 25 (6.4) 12 (3.1) 25 (6.4)
Flexural deformities Over-at-the-knee Calf knee Upright Dropped fetlock Clubfoot
28 (7.1) 6 (1.5) 6 (1.5) 24 (6.1) 51 (13.0)
22 (5.6) 3 (0.8) 5 (1.3) 23 (5.9) 27 (6.9)
8 (2.0) 1 (0.3) 2 (0.5) 8 (2.0) 27 (6.9)
13 (3.3) 1 (0.3) 0 2 (0.5) 7 (1.8)
1 (0.3) 0 2 (0.5) 1 (0.3) 8 (2.0)
14 (3.6) 5 (1.3) 4 (1.0) 21 (5.3) 36 (9.2)
54/115 (47.0%) in FT and 54/108 (50.0%) in TB at the first examination (P = 0.06); they did not differ between breeds at weaning (P = 0.21). During the first month, angular limb deformities were more often observed in FT whereas flexural limb deformities were more frequent in TB (P < 0.001) than in the other breeds. This difference was no longer apparent at weaning. During the first month, SF had fewer abnormal conformations of the fetlock than TB and FT (P = 0.01), with 35/69 (50.7%), 75/108 (69.4%) and 91/115 (79.1%) foals affected, respectively. There was no significant difference between the proportion of foals with fetlock varus in the
FT cohort (18/115, 15.7%) and those in the TB and SF cohorts (11/108, 10.2%; P = 0.09). At weaning, clubfoot was twice as common in FT (31/161, 19.3%) as in TB (12/133, 9.0%) and SF (8/99, 8.1%).
Discussion The aim of this study was to describe variations in forelimb conformation in foals from birth to weaning and to evaluate potential inter-breed differences in conformation over this period. Our study
C. Robert et al. / The Veterinary Journal 198 (2013) e75–e80
provides objective data on the frequency and the spontaneous evolution of limb deformities in foals by age group. Since it is difficult to make young horses adopt a consistent and repeatable posture, the foals were evaluated while walking on a horizontal surface. Conformation measurements vary strongly with the posture of the horse (Hunt et al., 1999; Weller et al., 2006a). Joint angulations appear more pronounced at walk than in the artificial square position, which supports the choice of dynamic conformation assessment (Unt et al., 2010). Distal limb conformation was assessed visually because this is the method commonly used by veterinarians and equestrians in practice (Kroekenstoel et al., 2006) and because it can be done quickly and easily. The advantages and limitations of this method have been discussed in the literature (van Weeren and Crevier-Denoix, 2006; Love et al., 2006). Subjective evaluations are expressions of opinion based on practical experience and are simple, cheap and convenient. However, Kroekenstoel et al. (2006) showed that visual assessment of the alignment of the distal limb often did not agree with radiographic measurements. The use of video recordings in combination with spatial calibration may be useful to evaluate limb rotation, which is difficult to assess visually as signalled by van Weeren and Crevier-Denoix (2006) found that two-dimensional methods cannot reliably quantify many faulty conformations. However, under field conditions, use of modern three-dimensional kinematic gait analysis equipment is often impractical, as well as being expensive. Conformational traits were evaluated on a four grade scale. This scale has been used in several studies to determine the prevalence of conformational defects in yearlings and to investigate the association between conformation and performance in TBs (Love et al., 2006; Santschi et al., 2006). Depending on the criteria used, j values for repeatability in conformation evaluation varied between 0.56 and 0.68. This is not as good as the results presented by Mawdsley et al. (1996) in their evaluation of body conformation traits (variation coefficient 50% of foals were affected by moderate to severe forelimb deformities at birth. This proportion was significantly lower (23.9%) at weaning. A total of 27 foals (6.9%) received either surgical, splint or corrective trimming/shoeing treatment. These interventions cannot by themselves explain the predominantly favourable evolution of limb deformities. However, it is possible that more foals received specific care, such as controlled exercise or more frequent corrective trimming, than identified in this study. For breeders, this is routine care often is not considered to be a specific intervention in the same way as orthopaedic shoeing or surgery. Therefore, some treatments may not have been reported. Angular limb deformities were present in more than half of the foals in their first month of life. A similar proportion was reported by Nannarone et al. (2003) in 17 foals at the age of 5 months of age. On the basis of on farm staff evaluation from 17 stud farms, O’Donohue et al. (1992) reported a 57.3% incidence of angular limb deformities in 1176 TB foals. Baxter (2011a) stated that the carpal region, followed by the fetlock region, are the sites most frequently affected and that most
e79
of these defects improved in the first months of life. In 119 TB foals followed from birth to yearling age and systematically examined from a frontal view, Santschi et al. (2006) also described a high prevalence of carpal valgus at birth (94%) that decreased sharply in the first months (71% at 46 days, 35% at 176 days). Outward deviation of the fetlock was present in 37% of newborn foals compared to 16% of foals at 176 days. Moderate angular limb deformities in young horses may almost be considered to be a physiological variant rather than a disease (Anderson and McIlwraith, 2004; Weller et al., 2006b). It has been suggested that mild valgus is not abnormal (Greet and Curtis, 2003; Santschi et al., 2006); as the foal grows and its chest broadens, the limbs assume a more perpendicular axis and the outward rotation diminishes (Leitch, 1985). Such a mild deformity may then end up as a correct limb conformation (Baxter, 2011a). Moreover, horses have natural growth correction mechanisms that lead to the spontaneous correction of many deformities in foals born with abnormal conformation (Bramlage, 1999). Cells of the physis that are loaded more heavily (on the concave side) grow faster, and those loaded less heavily (on the convex side) grow more slowly; the acceleration in growth on the concave side of the limb tends to lengthen that side until it is no longer concave or until the load on the physis is balanced along the axis of the limb (Bramlage, 1999). The evolution of serious carpal valgus, which was as favourable in treated foals as in untreated foals, supports these physiological correction mechanisms. The number of interventions to the fetlock was too small to draw any conclusions about their usefulness. The most frequently noted acquired angular deformities were in the feet and fetlocks. Toed-out and toed-in have been described as the most common conformational defects identified in TBs in training (Anderson et al., 2004) and in yearlings examined at sales (Love et al., 2006). In our study, these deviations were not the most common angular limb deformities at weaning, but their frequency increased between birth and weaning from 1% to 8.7% for toed-in foals and from 0% to 3.6% for toed-out foals. In our population, flexural limb deformities were not the predominant condition at birth, but were most frequent at weaning. As reported earlier (Kidd and Barr, 2002; Baxter, 2011b), the most common congenital flexural deformities affect the metacarpophalangeal joint and the carpus. The prevalence of dropped fetlocks decreased from 13% in 1-month-old foals to 6.1% in foals at weaning. Flaccidity of flexor tendons is a common condition in newborn foals (Kidd and Barr, 2002), affecting only the hind limbs in most cases, but sometimes also the forelimbs (Baxter, 2011b). This condition usually corrects spontaneously during the first weeks of life once the foal starts to exercise (Kidd and Barr, 2002; Jeffcott, 2004); the improvement results from the increase in muscle tone and better coordination (Leitch, 1985; Caron, 1988; Greet and Curtis, 2003). The prevalence of over-at-the-knee decreased from 31% to 12% from birth to weaning, supporting the observation that congenital carpal flexural deformities are usually self-correcting in a few weeks with controlled exercise (Kidd and Barr, 2002). Upright conformation was rare at birth. Although controversial (Kidd and Barr, 2002), intravenous oxytetracycline is popular as an initial treatment for congenital contractural deformities (Baxter, 2011b). Clearly we cannot draw valid conclusions from the small number of cases in this study; however, it seemed that administration of oxytetracycline was associated with more favourable changes than no treatment (8/9 vs. 6/11). Hyperflexion of the distal interphalangeal joint (club foot) was the most common form of acquired flexural deviation between birth and 6 months of age. This result is in agreement with that of a previous study (Greet and Curtis, 2003). Hyperflexion of the metacarpophalangeal joint is also a common acquired flexural deformity (Kidd and Barr, 2002; Jeffcott, 2004), but was observed
e80
C. Robert et al. / The Veterinary Journal 198 (2013) e75–e80
rarely in our study. This defect is usually seen at a later time, in yearlings (Kidd and Barr, 2002), typically around 18 months of age (Greet and Curtis, 2003). Acquired flexural deformities are grouped within the DOD complex because the potential causes and risk factors are similar (Baxter, 2011b); they tend to occur following periods of rapid growth or dietary imbalance. To our knowledge, inter-breed differences in the distribution of limb deformities in foals have not been reported previously. We found that FT and TB foals were more frequently affected by limb deformities than SF foals at birth; at weaning this difference had almost disappeared. As discussed above, most congenital defects tend to correct spontaneously in the first few months of life. In the present study, TB breeders usually paid more attention to conformation defects and deviations were treated early. In contrast, the management of FT and especially SF foals was more extensive, so that, in many cases, no direct action was taken when conformational defects were observed. One may assume that, in these breeds, congenital defects that do not correct spontaneously are less often treated and that acquired defects are often discovered late and treated less aggressively. The more interventional character of the management of TB foals may be justified by the high frequency of limb deformities in this breed and by the importance given to limb conformation at yearling auctions. However, FT and SF foals may also benefit from a more active approach, consisting of regular monitoring of foals during the first months, followed by interventions when deemed to be necessary. Conclusions This study shows that, in foals, carpal, fetlock and foot conformation undergo substantial changes between birth and weaning. The prevalence of congenital limb deformities is high, especially in TB race horses. Most defects improve spontaneously during the first months of life. However medical (e.g. oxytetracycline injection for flexural deformities), orthopaedic (splints, corrective trimming/shoeing) or surgical intervention may be required for severe deformation. The pattern of conformational development of foals described in this study provides a baseline against which individual forelimb deformities can be assessed. Conflict of interest statement None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper. Acknowledgements This work was supported by grants from the Haras Nationaux, the Conseil Régional de Basse Normandie, the Institut National de la Recherche Agronomique (INRA) and the French Ministry of Agriculture. References Anderson, T.M., McIlwraith, C.W., Douay, P., 2004. The role of conformation in musculoskeletal problems in the racing Thoroughbred. Equine Veterinary Journal 36, 571–575.
Anderson, T.M., McIlwraith, C.W., 2004. Longitudinal development of equine conformation from weanling to age 3 years in the Thoroughbred. Equine Veterinary Journal 36, 563–570. Auer, J.A., 2011. Angular limb deformities. In: Auer, J.A., Stick, J.A. (Eds.), Equine Surgery, Fourth Ed. Elsevier, St. Louis, Missouri, USA, pp. 1201–1221. Baxter, G.M., 2011a. Angular limb deformities. In: Baxter, G.M. (Ed.), Adams and Stashak’s Lameness in Horses, Sixth Ed. Wiley-Blackwell, Oxford, UK, pp. 1138– 1144. Baxter, G.M., 2011b. Flexural deformities. In: Baxter, G.M. (Ed.), Adams and Stashak’s Lameness in Horses, Sixth Ed. Wiley-Blackwell, Oxford, UK, pp. 1145–1154. Bramlage, L.R., 1999. The science and art of angular limb deformity correction. Equine Veterinary Journal 31, 182–183. Caron, J.P., 1988. Angular limb deformities in foals. Equine Veterinary Journal 20, 225–228. Greet, T.R.C., Curtis, S.J., 2003. Foot management in the foal and weanling. Veterinary Clinics of North America. Equine Practice 19, 501–517. Hunt, W.F., Thomas, V.G., Stiefel, W., 1999. Analysis of video-recorder images to determine linear and angular dimensions in the growing horse. Equine Veterinary Journal 31, 402–410. Jeffcott, L., 2004. Developmental diseases affecting growing horses. In: Juliand, D., Martin-Rosset, W. (Eds.), The Growing Horse: Nutrition and Prevention of Growth Disorders. Proceedings of the 2nd European Workshop on Equine Nutrition, Dijon, France, 15–17 January 2004. European Association of Animal Production (EAAP) Publication Number 14. Wageningen Academic Publishers, Wageningen, The Netherlands, pp. 243–245. http://www.eaap.org/docs/ Publications/eaap114%20-%204228654X.pdf (accessed 19 July 2013). Kidd, J.A., Barr, A.R.S., 2002. Flexural deformities in foals. Equine Veterinary Education 14, 311–321. Kroekenstoel, A.M., van Heel, M.C.V., van Weeren, P.R., Back, W., 2006. Developmental aspects of distal limb conformation in the horse: The potential consequences of uneven feet in foals. Equine Veterinary Journal 38, 652–656. Leitch, M., 1985. Musculoskeletal disorders in neonatal foals. Veterinary Clinics of North America. Equine Practice 1, 189–207. Lepeule, J., Bareille, N., Valette, J.-P., Seegers, H., Jacquet, S., Denoix, J.-M., Robert, C., 2008. Developmental orthopaedic disease in limbs of foals: Between-breed variations in the prevalence, location and severity at weaning. Animal 2, 284– 291. Love, S., Wyse, C.A., Stirk, A.J., Stear, M.J., Calver, P., Voute, L.C., Mellor, D.J., 2006. Prevalence, heritability and significance of musculoskeletal conformational traits in Thoroughbred yearlings. Equine Veterinary Journal 38, 597–603. Mawdsley, A., Kelly, E.P., Smith, F.H., Brophy, P.O., 1996. Linear assessment of the Thoroughbred horse: An approach to conformation evaluation. Equine Veterinary Journal 28, 461–467. Nannarone, S., Cavallucci, C., Macolino, G., Pepe, M., Bonanzinga, M., 2003. Orthopaedic disease: Effect of diet and stallion. In: van der Honing, Y. (Ed.), Book of Abstracts of the 54th Annual Meeting of the European Association for Animal Production (EAAP), Rome, Italy, 31 August–3 September 2003. EAAP Book of Abstract Number 9. Wageningen Academic Publishers, Wageningen, The Netherlands, p. 403. http://utcan.ut.ac.ir/member/conference/pakdel/ EAAP%202003.pdf (accessed 19 July 2013). O’Donohue, D.D., Smith, F.H., Strickland, K.L., 1992. The incidence of abnormal limb development in the Irish Thoroughbred from birth to 18 months. Equine Veterinary Journal 24, 305–309. Robert, C., Valette, J.-P., Jacquet, S., Lepeule, J., Denoix, J.-M., 2013. Study design for the investigation of likely aetiological factors of juvenile osteochondral conditions (JOCC) in foals and yearlings. The Veterinary Journal 197, 36–43. Santschi, E.M., Leibsle, S.R., Morehead, J.P., Prichard, M.A., Clayton, M.K., Keuler, N.S., 2006. Carpal and fetlock conformation of the juvenile Thoroughbred from birth to yearling auction age. Equine Veterinary Journal 38, 604–609. Unt, V.E., Evans, J., Reed, S., Pfau, T., Weller, R., 2010. Variation in frontal plane joint angles in horses. Equine Veterinary Journal 42, 444–450. Valette, J.-P., Robert, C., Denoix, J.-M., 2008. Use of linear and non-linear functions to describe the growth of young sport- and race-horses born in Normandy. Animal 2, 560–565. van Weeren, P.R., Crevier-Denoix, N., 2006. Equine conformation: Clues to performance and soundness? Equine Veterinary Journal 38, 591–596. Weller, R., Pfau, T., Babbage, D., Brittin, E., May, S.A., Wilson, A.M., 2006a. Reliability of conformational measurements in the horse using a three-dimensional motion analysis system. Equine Veterinary Journal 38, 610–615. Weller, R., Pfau, T., May, S.A., Wilson, A.M., 2006b. Variation in conformation in a cohort of National Hunt racehorses. Equine Veterinary Journal 38, 616–621. Weller, R., Pfau, T., Verheyen, K., May, S.A., Wilson, A.M., 2006c. The effect of conformation on orthopaedic health and performance in a cohort of National Hunt racehorses: Preliminary results. Equine Veterinary Journal 38, 622–627.
Contents lists available at ScienceDirect
The Veterinary Journal journal homepage: www.elsevier.com/locate/tvjl
Longitudinal development of equine forelimb conformation from birth to weaning in three different horse breeds C. Robert a,b,⇑, J.-P. Valette a,b, J.-M. Denoix b,c a
Université Paris Est, Ecole Nationale Vétérinaire d’Alfort, USC 957 BPLC, F-94700 Maisons-Alfort, France INRA, USC 957 BPLC, F-94700 Maisons-Alfort, France c Université Paris Est, Ecole Nationale Vétérinaire d’Alfort, CIRALE, F-14430 Goustranville, France b
a r t i c l e
i n f o
Keywords: Equine Conformation Forelimb Breed Growth Foal
a b s t r a c t There is limited published data on conformational changes in the forelimbs of growing foals. This study was designed to describe the changes in conformation of the carpus and distal forelimb from birth to weaning in foals of three different breeds. Evaluation of the conformation of the carpus, fetlock, pastern and foot was carried out in 134 Thoroughbreds, 162 French Trotters and 98 Selle Français (French Warmblood) within 1 month of age and then at approximately 2 month intervals until weaning at approximately 6 months of age. The prevalence of limb deviations decreased from birth to weaning. Angular limb deformities were the predominant conditions in the first month (63.6% of all observed limb deviations) and flexural limb deformities were the most common abnormalities at weaning. The most frequent congenital abnormalities were carpal valgus (42.1% of the foals), fetlock valgus (31.2%), over-at-the-knee (30.8%) and dropped fetlocks (13.0%), with French Trotters and Thoroughbred foals being more affected than Selle Français foals. During the study period, the carpal and fetlock conformation became less valgus. The predominant abnormalities at weaning were fetlock valgus (19.1%), club feet (13.0%) and fetlock varus (11.2%). These observations show that carpal, fetlock and foot conformations changed substantially from birth and weaning. There were significant conformational differences between the three breeds, especially in the first months of life. An understanding of the peculiarities of specific breeds may be useful for the evaluation of individual foal conformation. Ó 2013 Elsevier Ltd. All rights reserved.
Introduction Limb conformation has been considered to be an indicator of performance and orthopaedic health in horses for centuries. Horses are commonly selected on the basis of their conformation, in addition to performance and pedigree (Love et al., 2006; Santschi et al., 2006; Unt et al., 2010). Recent studies on the relationship between conformation and potential injury demonstrated that various clinical conditions were significantly associated with conformation variables (Anderson et al., 2004; Weller et al., 2006c). The assessment of distal limb conformation is part of the daily routine of equine clinicians in the evaluation of lameness and in pre-purchase examinations. Equine practitioners are commonly involved in the evaluation and treatment of conformational deviations in foals (Caron, 1988; Bramlage, 1999). The aims are to submit young horses with the best possible conformation for sale (at weaning or as yearlings) and to optimise conformation for future athletic performance.
⇑ Corresponding author. Tel.: +33 1 43967085. E-mail address: [email protected] (C. Robert). 1090-0233/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tvjl.2013.09.037
Most limb deformities are part of the developmental orthopaedic disease (DOD) complex (O’Donohue et al., 1992). The causes and mechanisms behind these deformities are complex and vary with the clinical entity; however, they are all associated with growth. The first clinical signs appear before 6 months of age and thoracic limbs are most commonly affected (Jeffcott, 2004). Previous studies demonstrated that growth in racehorses is most rapid in the first months of life, whereas in sport-horses it extends over their first years of life (Valette et al., 2008). Significant inter-breed differences in the distribution and severity of radiographic findings of the limb joints in foals at weaning have been recorded (Lepeule et al., 2008). There is extensive information available on variations in conformation in Thoroughbred (TB) horses within populations of mature horses (Mawdsley et al., 1996; Anderson et al., 2004; Weller et al., 2006b; Unt et al., 2010) and yearlings (Love et al., 2006; Santschi et al., 2006). Several studies have also evaluated changes in conformation with growth (O’Donohue et al., 1992; Anderson and McIlwraith, 2004), but very little information is available in Standardbred Trotter and Warmblood horses (Kroekenstoel et al., 2006). Procedures used for the management of limb deformities in foals include exercise and diet modification (Santschi et al., 2006), surgical techniques such as transphyseal bridging or perios-
e76
C. Robert et al. / The Veterinary Journal 198 (2013) e75–e80
teal elevation (Auer, 2011; Baxter, 2011a), and farrier interventions. However, the indications of these techniques remain controversial (Bramlage, 1999; Auer, 2011). Until recently, most foals showing some degree of angular deviation were subjected to surgical correction but a more conservative approach has been advocated in recent years (Auer, 2011; Baxter, 2011a). Conformation assessment is based largely on subjective criteria and empirical evidence (van Weeren and Crevier-Denoix, 2006). Determining whether and when intervention is indicated is difficult (Auer, 2011) in view of the subjective nature of the evaluation and of variations in individual conformation due to posture or muscular fatigue (Hunt et al., 1999). Given the frequency of requests for evaluation and correction of limb conformation in foals, objective background data on the prevalence and the changes in limb deformities associated with age and breed during the first months of life would be of value to practitioners expected to advise breeders and propose an appropriate treatment. The aims of this study were to describe variations in longitudinal development of forelimb conformation in foals from birth to weaning, considering both natural evolution and the impact of human intervention, and to evaluate potential inter-breed differences in conformation and in changes during this period, based on observational data collected in the field from a large sample size. The hypothesis tested was that mild congenital defects may be corrected naturally before weaning, while most moderate to severe congenital defects, or defects acquired after birth, do not completely correct spontaneously. We also tested the repeatability of the use of video for the examination and the longitudinal monitoring of limb deformities in foals. Materials and methods
2006). Deviations of the pastern and hoof were classified as ‘toed out’ or ‘toed in’. Flexural deformities (i.e. in a dorsopalmar plane) included ‘dropped fetlocks’ and ‘calf knee’ (back at the knee) (Love et al., 2006). The terms ‘over-at-the-knee’, ‘upright pastern’ and ‘clubfoot’ were used for hyperflexion of the carpus, fetlock joint and distal interphalangeal joints, respectively. Secondly, an overall score assessing the quality of limb balance was attributed to each forelimb. It reflected the average conformation observed through successive strides. The classification was based upon the dynamic examination alone. The static evaluation was used only to refine the score in case of doubt, for foals that could not be filmed in motion or when the quality of the recording was inadequate to properly evaluate the foal (e.g. foal not walking in a straight line). Grade 0 indicated correct conformation. Grade 1 was used for mild deviations, frequently observed in adult horses and considered to be minor defects or even the far end of biological variation of the normal situation. Nevertheless, although they may not be real (pathological) aberrations, conformations graded 1 were not considered to be normal (grade 0) because of their effect on the joint symmetry and balance, and therefore their potential consequences in the sport or race horse. Grades 2 and 3 (moderate to severe deviation, respectively) indicated the presence of a significant conformation defect. Fig. 1 illustrates the grading system.
Data analysis To evaluate intra-operator repeatability of the conformation evaluation, the films from 100 foals were viewed a second time by the same veterinarians. The various age groups, breeds and full range of anomalies were represented. The agreement on the presence or absence of a limb deformity and on the associated grade (0, 1, 2 or 3) between the first and second evaluations was assessed by calculating the observed percentage agreement (Po) and the kappa coefficient (j), which corrects for chance agreement. The prevalence of each type of limb deviation was calculated for each age group (1 month of age, 2.5 months of age and at weaning) and each breed (FT, SF and TB). The proportions of animals with specific limb deviations and combinations of such defects in the three breeds were compared using the v2 test. To analyse possible differences as a result of development, changes between birth and weaning were analysed using the general linear model (GLM) repeated measurements test. Statistical evaluation was performed with SAS software (SAS Institute), with P < 0.05 considered to be significant. The effects of corrective trimming/shoeing or surgical interventions were evaluated using the v2 test when numbers allowed.
Study population As part of a larger study on juvenile osteochondral conditions (JOCC) (Robert et al., 2013), the growth of 393 foals (202 fillies and 191 colts) born in 21 breeding farms in Normandy, France, was closely monitored. The foals belonged to the three main French breeds and included 134 TB, 162 French Standardbred Trotters (FT) and 98 Selle Français (French Warmbloods, SF). They were kept on pasture for periods ranging from a few hours to 24 h every day, depending on their age and on the practices of the farm. Foals were examined clinically for evidence of skeletal abnormalities at least three times between birth and weaning. Among the 393 foals, 292 were examined during their first month of life, with 72 animals being examined during their first week. All foals were examined again around 2.5 months of age (mean ± standard deviation 73 ± 29 days) and at weaning (172 ± 38 days). At each examination, conformation altering procedures performed, such as corrective shoeing or surgery, were recorded. Foals that had undergone interventions were not excluded from the analysis for purposes of comparison with untreated foals. The study was presented to the Ethics Committee of the Ecole Vétérinaire d’Alfort for approval, but the committee considered that it was not required to give an opinion, since there was no invasive procedure for foals and the only manipulation imposed in the study corresponding to usual interventions on breeding farms.
Results Repeatability of conformation evaluation The overall agreement on the presence or absence of limb deformity was good (Po = 82%; j = 0.61, 95% confidence interval, CI, 0.47–0.75). The same conformation assessment (type of deviation and grade) was made on 145/200 (72.5%) limbs. Among the 55 dissimilar diagnoses, 53 (96.4%) were due to grade 1 limb deformities
A
B
C 2
Conformation abnormalities and grading Any deviation present was recorded and classified. Carpal angular limb deviations (i.e. in a lateromedial plane) included valgus, varus and ‘bench knee’ (offset) (Love et al., 2006; Santschi et al., 2006; Baxter, 2011a). ‘Wind swept’ was used for foals with one leg with carpal valgus and the opposite with carpal varus (Baxter, 2011a). Frontal fetlock deviations were noted as valgus or varus (Santschi et al.,
D
3
Data collection The same veterinarian (CR) conducted all the physical examinations to ensure consistency in the evaluation procedure across all stud farms. The foals were first examined in a static position and then filmed while walking in a straight line on a hard and flat surface in hand, or freely near their dam, depending on farm practices. The video-films were made using a digital video camera (JVC GR-DVP-3) and four views of the foals were taken: front, rear, left side, right side. The films were viewed at a later time by three experienced veterinarians for detection of angular limb deviations (assessed from cranial and caudal views) and flexural deviations (assessed from lateral views).
1
12 3
123
3 12
1 12
3
Fig. 1. Principle of gradation of the most frequent limb deformities in foals. Normal conformation for young foals is schematically represented in black seen from the front view (A and B) and from the right side (C and D). (A) Fetlock valgus. (B) Carpal valgus. (C) Dropped fetlock (in red) and upright conformation (in green). (D) Overat-the-knee. 1, Mild deformity; 2, moderate deformity; 3, severe deformity.
e77
C. Robert et al. / The Veterinary Journal 198 (2013) e75–e80
that were missed (graded 0) at one of the two examination sessions and the last two were a grade 1 carpal valgus noted as carpal varus at the second assessment and a grade 1 fetlock varus noted as fetlock valgus. The agreement on the exact grade (0, 1, 2 or 3) was moderate (Po = 73%; j = 0.56, 95% CI 0.46–0.66). Considering grade 2 and 3 deformities together, the overall agreement on the presence of moderate to severe deviation was good (Po = 92%; j = 0.68, 95% CI 0.54–0.82). Among the 105 limbs where deformities were identified at both evaluations, the overall agreement percentage for the severity was high (Po = 83%) and the agreement was good (j = 0.60, 95% CI 0.43–0.77). In most cases (96.4%), the disagreement in grading was limited to one grade (grade 1 vs. 2 or 2 vs. 3). Prevalence of limb deviations The majority of foals (258/292, 88.4%) examined during their first month were presented with at least one limb deviation graded P1 and 135/258 (52.3%) affected foals had at least one deviation graded 2 or 3. The prevalence and the severity of limb deviations (Table 1) decreased linearly with increasing age (P < 0.01). Most deviations observed at the first examination involved the carpus (185/292, 63.4% of affected foals) or the fetlock (181/292, 62.0% of affected foals). In affected foals, 111/185 (60%) carpal deformities and 88/181 (48.6%) fetlock deformities were considered to be moderate to severe (grade 2 or 3), while 138/185 (74.6%) carpal deformities and 102/181 (56.4%) fetlock deformities were bilateral. At weaning, fetlock deviations (147/393, 37.4%) were more frequent (P < 0.01) than carpal (73/393, 18.6%) or foot deviations (91/ 393, 23.1%), but there were no significant differences in severity; 68/147 (46.3%) fetlock, 31/73 (42.5%) carpal and 33/91 (36.3%) foot deviations were graded 2 or 3. Among the lesions detected at weaning, half of the deviations on the carpus (38/73, 52%) had been observed at the time of first examination; this proportion of congenital deviations was significantly lower in the fetlock (32/ 147, 21.8%) and foot (8/91, 8.8%) (P < 0.05). Irrespective of the joint, 188/257 (73.2%) acquired deviations appeared between 3 months of age and weaning. Angular limb deviations Angular limb deviations were the predominant condition found in the first month of life, representing 288/453 (63.6%) of all observed limb deviations. Carpal valgus and fetlock valgus were the most frequent conditions (Table 2), with 123/292 (42.1%) and 91/ 292 (31.2%) foals affected, respectively. Most carpal valgus deviations (81/123, 65.8%) corrected naturally before 3 months of age and only 22/123 (17.9%) were still present at weaning. Fetlock valgus cases usually corrected spontaneously between 3 and 6 months of age, but 18/91 (19.8%) were still present at weaning. Angular limb deviations were much less frequent at weaning than at birth. Fetlock valgus (75/393, 19.1%), fetlock varus (44/ 393, 11.2%) and carpal valgus (41/393, 10.4%) were the most frequent deviations, half of the cases being graded 2 or 3 (Table 3). A proportion of foals with fetlock valgus (20/75, 26.7%) and varus (9/44, 20.4%) observed at weaning had already been noticed at
the first examination, but many of these conditions (valgus: 24/ 75, 32%; varus: 25/44, 56.8%) were identified for the first time at weaning. However, 24/41 (58.5%) carpal valgus cases noted at weaning were already present at 1 month of age. Eight foals underwent periosteal stripping because of severe carpal valgus at a mean age (± standard error) of 59 (±17) days; in four of these foals, the defect had completely disappeared or had become mild at weaning, whereas in the other four foals the valgus was still present and was grade 2 or 3 at weaning. Two Thoroughbred foals with a grade 2 fetlock valgus at 1 month of age received orthopaedic treatment (splint or medial acrylic hoof extension) and stall rest, which resulted in an improvement of their condition (grade 1 at weaning). Fetlock varus (one graded 3 and two graded 2) was treated in 3/19 affected foals with regular hoof trimming (2 foals) or periosteal elevation (1 foal); none was significantly improved at weaning. Flexural limb deformities Flexural limb deformities were less frequent (165/453, 36.4% of all observed limb deviations) than angular limb deformities at the first examination of the foals. Over-at-the-knee and dropped fetlocks were the more frequent conditions, with 30.8% and 13.0% of the foals affected, respectively (Table 2). Most of these deformities had disappeared at the age of 3 months and only 11/90 (12.2%) and 2/38 (5.3%), respectively, were still present at weaning. Flexural limb deformities were the predominant condition at weaning (369/589, 62.6% of limb deformities). Clubfeet (51/393, 13.0% of foals), followed by over-at-the-knee (28/393, 7.1%) and dropped fetlocks (24/393, 6.1%), were the more frequent conditions (Table 3). Most of these (clubfeet: 36/51, 70.6%; over-atthe-knee: 14/28, 50.0%; dropped fetlocks: 21/24, 87.5%) were first observed at weaning. Two foals with marked digital hyperextension (grade 3) in one or both forelimbs at birth had extended-heel glue-on shoes applied for a few weeks; this resulted in complete recovery in one foal and limited improvement (grade 2) in the other one. Nine foals with clubfoot or upright conformation (grade 2 or 3) at birth received oxytetracycline intravenously once or twice during their first weeks of life. This was combined with stall rest in most cases, and with dorsal hoof extension using acrylic (one foal), foot plate (one foal) and cast (one foal). Except for the last foal, which was also affected by severe hock osteochondrosis, all the defects had disappeared or were considered to be mild at weaning. The evolution tended to be less favourable (P = 0.09) in the 11 untreated foals, with five still affected with grade 2 or 3 defects at weaning. Three foals with acquired club-foot (diagnosed between 2.5 and 6 months of age) were given corrective trimming/shoeing and stall rest; the problem had disappeared at weaning in the youngest foal and improved in the two older ones. Inter-breed variations All anomalies combined, SF had fewer defects than FT and TB, both at birth (P < 0.01) and at weaning (P = 0.04). The proportions of foals with grade 2 or 3 deformities were 27/69 (39.7%) in SF,
Table 1 Prevalence of limb deformities in the forelimbs depending on the age of foals. Age
Number of foals evaluated n
No forelimb deformity n (%)
Moderate (grade 2) to severe (grade 3) forelimb deformity n (%)
0–7 days 8–30 days 1–3 months Weaning
72 230 328 393
5 (6.9) 27 (11.7) 97 (29.6) 159 (40.5)
40 (55.6) 100 (43.5) 103 (31.4) 94 (23.9)
e78
C. Robert et al. / The Veterinary Journal 198 (2013) e75–e80
Table 2 Prevalence of foals showing deviations of the forelimbs at 1 month of age in 292 foals (scored on three occasions) and evolution of this prevalence at 3 and 6 months of age in the same foals. Age Severity Symmetry Foals affected Angular deformities Carpal valgusa,b Carpal valgus NTa,b Carpal varus Bench knee Wind-swepta,b Fetlock valgusa Fetlock valgus NTa Fetlock varusa Fetlock varus NTa Toed-out Toed-inb Flexural deformities Over-at-the-kneea,b Calf knee Uprighta Upright NTa Dropped fetlocka Dropped fetlock NTa Clubfoot Clubfoot NT
3 months
6 months
1–3 Unilateral and bilateral n (%)
1 month 1–3 Bilateral only n (%)
2–3 Unilateral and bilateral n (%)
1–3 Unilateral and bilateral n (%)
1–3 Unilateral and bilateral n (%)
123 (42.1) 115 (39.4) 4 (1.4) 2 (0.7) 28 (9.6) 91 (31.2) 89 (30.5) 37 (12.7) 34 (11.6) 0 3 (1.0)
64 (21.9) 62 (21.2) 0 2 (0.7) 28 (9.6) 28 (9.6) 28 (9.6) 13 (4.5) 12 (4.1) 0 2 (0.7)
77 (26.4) 69 (23.6) 3 (1.0) 2 (0.7) 15 (5.1) 33 (11.3) 31 (10.6) 19 (6.5) 16 (5.5) 0 1 (0.3)
42 (14.4) 34 (11.6) 0 0 18 (6.2) 48 (16.4) 46 (15.8) 16 (5.5) 13 (4.5) 0 1 (0.3)
22 (7.5) 16 (5.5) 0 0 7 (2.4) 18 (6.2) 16 (5.5) 9 (3.1) 6 (2.1) 0 1 (0.3)
90 (30.8) 5 (1.7) 14 (4.8) 8 (2.7) 38 (13.0) 36 (12.3) 18 (6.2) 15 (5.1)
84 (28.8) 5 (1.7) 13 (4.5) 7 (2.4) 36 (12.3) 35 (12.0) 13 (4.5) 13 (4.5)
53 (18.2) 4 (1.4) 6 (2.1) 0 (7.2) 21 (7.2) 19 (6.5) 14 (4.8) 11 (3.8)
25 (8.6) 1 (0.3) 3 (1.0) 0 4 (1.4) 3 1.0) 11 (3.8) 9 (3.1)
11 (3.8) 1 (0.3) 1 (0.3) 0 2 (0.7) 1 (0.3) 9 (3.1) 8 (2.7)
For deviations for which some foals received surgical treatment or corrective trimming/shoeing, data from untreated foals appear on a second line with the annotation NT, not treated. a Significant reduction in the number of congenital deviations between the first month and weaning. b Significant difference in global prevalence between the first month and weaning (corrected congenital deviations not balanced by acquired deviations or vice versa).
Table 3 Prevalence of deviations of the forelimbs of 393 foals at weaning and examination when these were first noted. Age at first detection Prevalence at weaning
First examination
Severity Symmetry
1–3 Unilateral and bilateral
1–3 Bilateral only
2–3 Unilateral and bilateral
Foals affected
3 months
6 months
1–3 Unilateral and bilateral
n (%)
n (%)
n (%)
n (%)
n (%)
n (%)
Angular deformities Carpal valgus Carpal varus Bench knee Wind-swept Fetlock valgus Fetlock varus Toed-out Toed-in
41 (10.4) 2 (0.5) 2 (0.5) 8 (2.0) 75 (19.1) 44 (11.2) 14 (3.6) 34 (8.7)
13 (3.3) 0 2 (0.5) 8 (2.0) 18 (4.6) 13 (3.3) 11 (2.8) 12 (3.1)
23 (5.9) 1 (0.3) 1 (0.3) 3 (0.8) 42 (10.7) 22 (5.6) 2 (0.5) 9 (2.3)
24 (6.1) 0 0 1 (0.3) 20 (5.1) 9 (2.3) 0 1 (0.3)
4 (1.0) 0 0 2 (0.5) 31 (7.9) 10 (2.5) 2 (0.5) 8 (2.0)
13 (3.3) 2 (0.5) 2 (0.5) 5 (1.3) 24 (6.1) 25 (6.4) 12 (3.1) 25 (6.4)
Flexural deformities Over-at-the-knee Calf knee Upright Dropped fetlock Clubfoot
28 (7.1) 6 (1.5) 6 (1.5) 24 (6.1) 51 (13.0)
22 (5.6) 3 (0.8) 5 (1.3) 23 (5.9) 27 (6.9)
8 (2.0) 1 (0.3) 2 (0.5) 8 (2.0) 27 (6.9)
13 (3.3) 1 (0.3) 0 2 (0.5) 7 (1.8)
1 (0.3) 0 2 (0.5) 1 (0.3) 8 (2.0)
14 (3.6) 5 (1.3) 4 (1.0) 21 (5.3) 36 (9.2)
54/115 (47.0%) in FT and 54/108 (50.0%) in TB at the first examination (P = 0.06); they did not differ between breeds at weaning (P = 0.21). During the first month, angular limb deformities were more often observed in FT whereas flexural limb deformities were more frequent in TB (P < 0.001) than in the other breeds. This difference was no longer apparent at weaning. During the first month, SF had fewer abnormal conformations of the fetlock than TB and FT (P = 0.01), with 35/69 (50.7%), 75/108 (69.4%) and 91/115 (79.1%) foals affected, respectively. There was no significant difference between the proportion of foals with fetlock varus in the
FT cohort (18/115, 15.7%) and those in the TB and SF cohorts (11/108, 10.2%; P = 0.09). At weaning, clubfoot was twice as common in FT (31/161, 19.3%) as in TB (12/133, 9.0%) and SF (8/99, 8.1%).
Discussion The aim of this study was to describe variations in forelimb conformation in foals from birth to weaning and to evaluate potential inter-breed differences in conformation over this period. Our study
C. Robert et al. / The Veterinary Journal 198 (2013) e75–e80
provides objective data on the frequency and the spontaneous evolution of limb deformities in foals by age group. Since it is difficult to make young horses adopt a consistent and repeatable posture, the foals were evaluated while walking on a horizontal surface. Conformation measurements vary strongly with the posture of the horse (Hunt et al., 1999; Weller et al., 2006a). Joint angulations appear more pronounced at walk than in the artificial square position, which supports the choice of dynamic conformation assessment (Unt et al., 2010). Distal limb conformation was assessed visually because this is the method commonly used by veterinarians and equestrians in practice (Kroekenstoel et al., 2006) and because it can be done quickly and easily. The advantages and limitations of this method have been discussed in the literature (van Weeren and Crevier-Denoix, 2006; Love et al., 2006). Subjective evaluations are expressions of opinion based on practical experience and are simple, cheap and convenient. However, Kroekenstoel et al. (2006) showed that visual assessment of the alignment of the distal limb often did not agree with radiographic measurements. The use of video recordings in combination with spatial calibration may be useful to evaluate limb rotation, which is difficult to assess visually as signalled by van Weeren and Crevier-Denoix (2006) found that two-dimensional methods cannot reliably quantify many faulty conformations. However, under field conditions, use of modern three-dimensional kinematic gait analysis equipment is often impractical, as well as being expensive. Conformational traits were evaluated on a four grade scale. This scale has been used in several studies to determine the prevalence of conformational defects in yearlings and to investigate the association between conformation and performance in TBs (Love et al., 2006; Santschi et al., 2006). Depending on the criteria used, j values for repeatability in conformation evaluation varied between 0.56 and 0.68. This is not as good as the results presented by Mawdsley et al. (1996) in their evaluation of body conformation traits (variation coefficient 50% of foals were affected by moderate to severe forelimb deformities at birth. This proportion was significantly lower (23.9%) at weaning. A total of 27 foals (6.9%) received either surgical, splint or corrective trimming/shoeing treatment. These interventions cannot by themselves explain the predominantly favourable evolution of limb deformities. However, it is possible that more foals received specific care, such as controlled exercise or more frequent corrective trimming, than identified in this study. For breeders, this is routine care often is not considered to be a specific intervention in the same way as orthopaedic shoeing or surgery. Therefore, some treatments may not have been reported. Angular limb deformities were present in more than half of the foals in their first month of life. A similar proportion was reported by Nannarone et al. (2003) in 17 foals at the age of 5 months of age. On the basis of on farm staff evaluation from 17 stud farms, O’Donohue et al. (1992) reported a 57.3% incidence of angular limb deformities in 1176 TB foals. Baxter (2011a) stated that the carpal region, followed by the fetlock region, are the sites most frequently affected and that most
e79
of these defects improved in the first months of life. In 119 TB foals followed from birth to yearling age and systematically examined from a frontal view, Santschi et al. (2006) also described a high prevalence of carpal valgus at birth (94%) that decreased sharply in the first months (71% at 46 days, 35% at 176 days). Outward deviation of the fetlock was present in 37% of newborn foals compared to 16% of foals at 176 days. Moderate angular limb deformities in young horses may almost be considered to be a physiological variant rather than a disease (Anderson and McIlwraith, 2004; Weller et al., 2006b). It has been suggested that mild valgus is not abnormal (Greet and Curtis, 2003; Santschi et al., 2006); as the foal grows and its chest broadens, the limbs assume a more perpendicular axis and the outward rotation diminishes (Leitch, 1985). Such a mild deformity may then end up as a correct limb conformation (Baxter, 2011a). Moreover, horses have natural growth correction mechanisms that lead to the spontaneous correction of many deformities in foals born with abnormal conformation (Bramlage, 1999). Cells of the physis that are loaded more heavily (on the concave side) grow faster, and those loaded less heavily (on the convex side) grow more slowly; the acceleration in growth on the concave side of the limb tends to lengthen that side until it is no longer concave or until the load on the physis is balanced along the axis of the limb (Bramlage, 1999). The evolution of serious carpal valgus, which was as favourable in treated foals as in untreated foals, supports these physiological correction mechanisms. The number of interventions to the fetlock was too small to draw any conclusions about their usefulness. The most frequently noted acquired angular deformities were in the feet and fetlocks. Toed-out and toed-in have been described as the most common conformational defects identified in TBs in training (Anderson et al., 2004) and in yearlings examined at sales (Love et al., 2006). In our study, these deviations were not the most common angular limb deformities at weaning, but their frequency increased between birth and weaning from 1% to 8.7% for toed-in foals and from 0% to 3.6% for toed-out foals. In our population, flexural limb deformities were not the predominant condition at birth, but were most frequent at weaning. As reported earlier (Kidd and Barr, 2002; Baxter, 2011b), the most common congenital flexural deformities affect the metacarpophalangeal joint and the carpus. The prevalence of dropped fetlocks decreased from 13% in 1-month-old foals to 6.1% in foals at weaning. Flaccidity of flexor tendons is a common condition in newborn foals (Kidd and Barr, 2002), affecting only the hind limbs in most cases, but sometimes also the forelimbs (Baxter, 2011b). This condition usually corrects spontaneously during the first weeks of life once the foal starts to exercise (Kidd and Barr, 2002; Jeffcott, 2004); the improvement results from the increase in muscle tone and better coordination (Leitch, 1985; Caron, 1988; Greet and Curtis, 2003). The prevalence of over-at-the-knee decreased from 31% to 12% from birth to weaning, supporting the observation that congenital carpal flexural deformities are usually self-correcting in a few weeks with controlled exercise (Kidd and Barr, 2002). Upright conformation was rare at birth. Although controversial (Kidd and Barr, 2002), intravenous oxytetracycline is popular as an initial treatment for congenital contractural deformities (Baxter, 2011b). Clearly we cannot draw valid conclusions from the small number of cases in this study; however, it seemed that administration of oxytetracycline was associated with more favourable changes than no treatment (8/9 vs. 6/11). Hyperflexion of the distal interphalangeal joint (club foot) was the most common form of acquired flexural deviation between birth and 6 months of age. This result is in agreement with that of a previous study (Greet and Curtis, 2003). Hyperflexion of the metacarpophalangeal joint is also a common acquired flexural deformity (Kidd and Barr, 2002; Jeffcott, 2004), but was observed
e80
C. Robert et al. / The Veterinary Journal 198 (2013) e75–e80
rarely in our study. This defect is usually seen at a later time, in yearlings (Kidd and Barr, 2002), typically around 18 months of age (Greet and Curtis, 2003). Acquired flexural deformities are grouped within the DOD complex because the potential causes and risk factors are similar (Baxter, 2011b); they tend to occur following periods of rapid growth or dietary imbalance. To our knowledge, inter-breed differences in the distribution of limb deformities in foals have not been reported previously. We found that FT and TB foals were more frequently affected by limb deformities than SF foals at birth; at weaning this difference had almost disappeared. As discussed above, most congenital defects tend to correct spontaneously in the first few months of life. In the present study, TB breeders usually paid more attention to conformation defects and deviations were treated early. In contrast, the management of FT and especially SF foals was more extensive, so that, in many cases, no direct action was taken when conformational defects were observed. One may assume that, in these breeds, congenital defects that do not correct spontaneously are less often treated and that acquired defects are often discovered late and treated less aggressively. The more interventional character of the management of TB foals may be justified by the high frequency of limb deformities in this breed and by the importance given to limb conformation at yearling auctions. However, FT and SF foals may also benefit from a more active approach, consisting of regular monitoring of foals during the first months, followed by interventions when deemed to be necessary. Conclusions This study shows that, in foals, carpal, fetlock and foot conformation undergo substantial changes between birth and weaning. The prevalence of congenital limb deformities is high, especially in TB race horses. Most defects improve spontaneously during the first months of life. However medical (e.g. oxytetracycline injection for flexural deformities), orthopaedic (splints, corrective trimming/shoeing) or surgical intervention may be required for severe deformation. The pattern of conformational development of foals described in this study provides a baseline against which individual forelimb deformities can be assessed. Conflict of interest statement None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper. Acknowledgements This work was supported by grants from the Haras Nationaux, the Conseil Régional de Basse Normandie, the Institut National de la Recherche Agronomique (INRA) and the French Ministry of Agriculture. References Anderson, T.M., McIlwraith, C.W., Douay, P., 2004. The role of conformation in musculoskeletal problems in the racing Thoroughbred. Equine Veterinary Journal 36, 571–575.
Anderson, T.M., McIlwraith, C.W., 2004. Longitudinal development of equine conformation from weanling to age 3 years in the Thoroughbred. Equine Veterinary Journal 36, 563–570. Auer, J.A., 2011. Angular limb deformities. In: Auer, J.A., Stick, J.A. (Eds.), Equine Surgery, Fourth Ed. Elsevier, St. Louis, Missouri, USA, pp. 1201–1221. Baxter, G.M., 2011a. Angular limb deformities. In: Baxter, G.M. (Ed.), Adams and Stashak’s Lameness in Horses, Sixth Ed. Wiley-Blackwell, Oxford, UK, pp. 1138– 1144. Baxter, G.M., 2011b. Flexural deformities. In: Baxter, G.M. (Ed.), Adams and Stashak’s Lameness in Horses, Sixth Ed. Wiley-Blackwell, Oxford, UK, pp. 1145–1154. Bramlage, L.R., 1999. The science and art of angular limb deformity correction. Equine Veterinary Journal 31, 182–183. Caron, J.P., 1988. Angular limb deformities in foals. Equine Veterinary Journal 20, 225–228. Greet, T.R.C., Curtis, S.J., 2003. Foot management in the foal and weanling. Veterinary Clinics of North America. Equine Practice 19, 501–517. Hunt, W.F., Thomas, V.G., Stiefel, W., 1999. Analysis of video-recorder images to determine linear and angular dimensions in the growing horse. Equine Veterinary Journal 31, 402–410. Jeffcott, L., 2004. Developmental diseases affecting growing horses. In: Juliand, D., Martin-Rosset, W. (Eds.), The Growing Horse: Nutrition and Prevention of Growth Disorders. Proceedings of the 2nd European Workshop on Equine Nutrition, Dijon, France, 15–17 January 2004. European Association of Animal Production (EAAP) Publication Number 14. Wageningen Academic Publishers, Wageningen, The Netherlands, pp. 243–245. http://www.eaap.org/docs/ Publications/eaap114%20-%204228654X.pdf (accessed 19 July 2013). Kidd, J.A., Barr, A.R.S., 2002. Flexural deformities in foals. Equine Veterinary Education 14, 311–321. Kroekenstoel, A.M., van Heel, M.C.V., van Weeren, P.R., Back, W., 2006. Developmental aspects of distal limb conformation in the horse: The potential consequences of uneven feet in foals. Equine Veterinary Journal 38, 652–656. Leitch, M., 1985. Musculoskeletal disorders in neonatal foals. Veterinary Clinics of North America. Equine Practice 1, 189–207. Lepeule, J., Bareille, N., Valette, J.-P., Seegers, H., Jacquet, S., Denoix, J.-M., Robert, C., 2008. Developmental orthopaedic disease in limbs of foals: Between-breed variations in the prevalence, location and severity at weaning. Animal 2, 284– 291. Love, S., Wyse, C.A., Stirk, A.J., Stear, M.J., Calver, P., Voute, L.C., Mellor, D.J., 2006. Prevalence, heritability and significance of musculoskeletal conformational traits in Thoroughbred yearlings. Equine Veterinary Journal 38, 597–603. Mawdsley, A., Kelly, E.P., Smith, F.H., Brophy, P.O., 1996. Linear assessment of the Thoroughbred horse: An approach to conformation evaluation. Equine Veterinary Journal 28, 461–467. Nannarone, S., Cavallucci, C., Macolino, G., Pepe, M., Bonanzinga, M., 2003. Orthopaedic disease: Effect of diet and stallion. In: van der Honing, Y. (Ed.), Book of Abstracts of the 54th Annual Meeting of the European Association for Animal Production (EAAP), Rome, Italy, 31 August–3 September 2003. EAAP Book of Abstract Number 9. Wageningen Academic Publishers, Wageningen, The Netherlands, p. 403. http://utcan.ut.ac.ir/member/conference/pakdel/ EAAP%202003.pdf (accessed 19 July 2013). O’Donohue, D.D., Smith, F.H., Strickland, K.L., 1992. The incidence of abnormal limb development in the Irish Thoroughbred from birth to 18 months. Equine Veterinary Journal 24, 305–309. Robert, C., Valette, J.-P., Jacquet, S., Lepeule, J., Denoix, J.-M., 2013. Study design for the investigation of likely aetiological factors of juvenile osteochondral conditions (JOCC) in foals and yearlings. The Veterinary Journal 197, 36–43. Santschi, E.M., Leibsle, S.R., Morehead, J.P., Prichard, M.A., Clayton, M.K., Keuler, N.S., 2006. Carpal and fetlock conformation of the juvenile Thoroughbred from birth to yearling auction age. Equine Veterinary Journal 38, 604–609. Unt, V.E., Evans, J., Reed, S., Pfau, T., Weller, R., 2010. Variation in frontal plane joint angles in horses. Equine Veterinary Journal 42, 444–450. Valette, J.-P., Robert, C., Denoix, J.-M., 2008. Use of linear and non-linear functions to describe the growth of young sport- and race-horses born in Normandy. Animal 2, 560–565. van Weeren, P.R., Crevier-Denoix, N., 2006. Equine conformation: Clues to performance and soundness? Equine Veterinary Journal 38, 591–596. Weller, R., Pfau, T., Babbage, D., Brittin, E., May, S.A., Wilson, A.M., 2006a. Reliability of conformational measurements in the horse using a three-dimensional motion analysis system. Equine Veterinary Journal 38, 610–615. Weller, R., Pfau, T., May, S.A., Wilson, A.M., 2006b. Variation in conformation in a cohort of National Hunt racehorses. Equine Veterinary Journal 38, 616–621. Weller, R., Pfau, T., Verheyen, K., May, S.A., Wilson, A.M., 2006c. The effect of conformation on orthopaedic health and performance in a cohort of National Hunt racehorses: Preliminary results. Equine Veterinary Journal 38, 622–627.
