Authors
Pere M. Parés-Casanova
Abstract
This article describes the angular hoof conformation of the Pyrenean Catalan Horse breed. Digital images of the hooves were obtained from a sample of 110 healthy animals (71 adults and 39 foals) and 4 hoof angles were measured (front face hoof, heel, coronet, and pastern angles). It was shown that angle values were influenced by the age and body score condition. Foals tended to present higher coronet and front face angles. Angles tended to be lower with better body condition. Sex, coat, and presence/absence of leg whites had no influence on angular measurements. Mean values for adult animals were finally obtained and presented as reference values for this breed. These measurements fall within the normal ranges described for the horse, although a high degree of variability was detected. These studies represent important future considerations for the assessment of animals belonging to this breed.
Introduction
The hoof is a dynamic structure, capable of modifying its conformation to the forces placed on it (Wilson et al. 2009). Its primary function is to bear weight, absorb shock, and provide traction. Ideal hoof conformation has been a subject of much attention within the equine literature. Some of this information has been the result of lay observations and associations identified by equine practitioners over many years. Improper hoof care reduces the ability of the foot to perform these functions and increases the amount of stress applied to the joints, tendons, and ligaments of the equine limb (Budras, Sack, and Röck 2009).
One of the most commonly misunderstood topics with respect to equine hooves is the subject of hoof angles (Sellke, Patan-Zugaj, and Witter 2020). Angles of the equine hoof can be measured in order to assess and classify hoof shapes, to quantify asymmetries and changes during training or body condition, and to measure the effect of trimming or application of different horseshoes (Nicolai et al. 2017) (Leśniak et al. 2019) (Sellke, Patan-Zugaj, and Witter 2020).
When hoof care professionals speak of “hoof angles,” they are referring mostly to the angle the dorsal hoof wall with respect to the ground. A hoof angle is considered to be “normal” when the three phalanges are aligned so that their dorsal wall is parallel with the pastern (Clayton 1990) (Nicolai et al. 2017). In the front feet the foot–pastern axis should be between 45° and 50° to the ground (Dyce, Sack, and Wensig 1999). The hind feet are usually more pointed than the front and slightly more upright (50° to 55°), so a correct foot-pastern axis is also within this range (Dyce, Sack, and Wensig 1999). If the slope of the front face of the hoof exceeds 60ºs, as an upright heel (“Club Footed”), there can appear a contracture of the deep digital flexor tendon. The slope of the hoof wall can be steeper than the pastern (“Coon-Footed”), too, this fault being often associated with long sloping pasterns that tend to the horizontal. A decrease in the angle relative to the ground results in the heels sinking and becoming underrun (Nicolai et al. 2017). If the dorsal hoof angle is greater than that of the pastern, the angle of the heels relative to the ground is increased, reducing the load on the palmar aspect of the foot (Nicolai et al. 2017). In any case, hoof conformation can be altered by human intervention, such as hoof trimming and the application of horseshoes.
A pattern of trimming and hoof conformation has been developed from observations of feral horses grazing in semi-arid environments (Gordon et al. 2013) and in semi-feral Mongolians in rangeland steppe (Gordon et al. 2013). The Pyrenean Catalan Horse is the only indigenous horse breed in Catalonia, raised in the harsh conditions of the Eastern Pyrenees (Infante Gil 2011). Hits horse is warm-blood, compact, broad-built, with rather short limbs, weighing 650–750 kg (Infante Gil 2011). Genetic analysis suggests that it is closely related to the Breton and Comtois breeds (Infante Gil 2011) (Parés-Casanova, Samuel, and Pelegrín 2016). Formerly they were used primarily for mule production, but they are currently mainly bred for meat production. When selected for sacrifice, they are gathered in paddocks and receive additional feeding with hay and concentrates during the last 2-3 months before slaughter, at 10-12 months of age (“poltres”, admitted body weight about 350 kg (Parés-Casanova 2011). This breed thrives in a free-roaming lifestyle and consuming a varied and natural diet, being reared outdoors throughout the year, normally without receiving additional food beside hay in winter. During summer months (from May to October) they graze on high altitude mountain grasses (1200-2800 masl).
Animals of this breed do not receive any hoof care, trimming, or shoeing (Parés-Casanova 2011) but clinical hoof wall problems are rarely found, being the “flat foot” -the hoof wall flaring outwards, quarters heavily sloping, low heels, wide hoof (frog overgrowth, widely spaced heels and bars), hoof cracks and non-severe postlaminitis defects, occasional unclinical flaws (pers. obs.). Environmental (natural) conditions and low intentional human handling (no breeding and selection programs) have led over the ages to harsh animals well adapted to the territory.
The aim of this study was therefore to investigate:
1. The values of hoof angles in this local pure horse breed, which is not subjected to hoof trimming and maintained under extensive conditions
2. the relationship between hoof angles for all limbs
3. the comparison with other non-trimmed breeds.
The presented study constitutes the first contribution to hoof angular description of Pyrenean Catalan Horse, our data providing moreover an understanding of no trimming effects on hoof conformation. The presented study can be also of practical significance as a basis for other studies among other Iberian extensively managed horse breeds, such as “Burguete” and “Hispano-Bretón”.
Material and methods
The study was conducted on a total of 110 animals (71 adults -8 ♂ and 63 ♀- and 39 foals -17 ♂ and 22 ♀-) belonging to Pyrenean Catalan Horse (Figure 1) in three different summer grassland areas in the Cerdanya county (Catalan Pyrenees, NE Catalonia) during summer 2020. Body Score Condition in a 10-point scale (adapted from Carroll and Huntington 1988), sex and coat were registered. Leg white marks were also registered. No animal presented signs of lameness. Individual digital images were obtained on the lateral aspect of each hoof separately. Horses were standing squarely while pictures were taken.
1.
Digital pictures were obtained using a compact digital camera, which was at right angles to the axis of the foot at ground level. Images were subsequently saved as gif files for later analysis. Then we visualized imaginary lines between pictures and noted angles on the lines for all 4 limbs (Figure 2):
1- Angulation of front face of hoof (“toe angle”, the degree between the front hoof wall -pars dorsalis- going up and flat ground)
2- angulation of heel (degree between the up-going heel -pars mobilis lateralis-wall and flat ground)
3- angulation of coronet (margo coronalis)
4- angulation of pastern (regio compedis).
The hooves of each leg were examined for each animal. A subsample of 36 hooves were measured twice in order to assess error. Measurements were obtained from digital pictures using the Digimizer® v. 5.4.7 software (available at https://www.digimizer.com/). Mean ± standard deviation, minimum and maximum and coefficient of variation values were calculated for each angulation. Angular data were log transformed for ulterior analysis. Preliminary analysis included a Wilcoxon W paired test to assess differences replicas. A one-way NPMANOVA with Mahalanobis distance compared right-left pairs for forelimbs and hindlimbs separately, and a MANOVA allowed the comparison between fore and hindlimb pairs. A two-way NPMANOVA assessed influence of qualitative traits (coat, age group, gender, coat, body condition and grassland area). Finally, a Principal Component Analysis (PCA) from var-covar matrix was done. All analysis were done with PAST v. 2.17c software (Hammer, Harper, and Ryan 2001). Confidence level was stablished at 95%.
Results
Replicated samples showed no statistical differences (W=6008, p=0.116), being the average error measurement of 6.13%. One-way NPMANOVA reflected no statistical differences between left-right pairs (p=0.697 and 0.343 for fore and hindlimbs respectively), so for ulterior analysis we made no consideration to side. MANOVA reflected statistical differences between fore and hindlimb pairs (Wilks’ λ=0.970, F4,435=3.293, p=0.0112). Heel angles were significantly higher (e.g. more obtuse) than the front face angle (W=8.11, p<<0.0001). There appeared no statistical differences between the angle of the front face of the hoof and the angle of the dorsal surface of the pastern (W=4.87, p=0.942). Morphometric traits were influenced by age (p=0.0001) and body condition (p=0.001, range 2.5 to 6.5). Foals tended to present higher coronet and front face angles, while angles tended to be lower with better body condition. Sex, coat and presence/absence of leg whites had no influence on angular measurements. Main descriptive statistics for adult individuals (with no gender separation) appear in table 1. Coefficients of variation reflected high variabilities, ranging from 11.1 to 26.9%. In PCA, 3 first Principal Components (PC) explained 100% of the total observed variance (PCA+PC2+PC3=77.70%+19.43%+2.86%), showing that front face, pastern, and coronet angles contributed most to the observed differences between fore and hind pairs (table 2). Heel angle contributed less to differentiation between fore and hind hooves, although all angles presented statistically significative differences between fore and hind pairs.
Discussion
Hoof constitutes an important element of horse conformation; otherwise, it will hamper the ability to perform certain tasks to a greater or lesser extent and thus will influence the usability of the animals. Despite differences in shape, hoof wall slope, and size, hooves should be proportional to the size of the horse (Łuszczyński et al. 2015). A horse should have roughly a 50-degree angle of the front wall of the hoof to the ground (Dyce, Sack, and Wensig 1999). Pyrenean horses present slightly higher values in hindlimbs, so they were more obtuse; in other words, forehooves presented angles comparatively smaller (“less pointed hooves”). The front and hind feet have different functions therefore their shape is distinctly different. The front feet bear approximately a 60% of the weight of the horse and are more rounded through the toe and quarters. The hind feet are used primarily for propulsion.
The angle, or line, of the hoof should match the angle of the dorsal surface of the pastern. If this angle is broken, it would indicate a poor trim due to either too much toe, a concave break in the line, or too much heel, a convex break in the line. Averaged coronet (“hairline”) angles fell in the range of 20-30º. If the hairline was less than 20º, the heels would be likely too high, and the coffin bone would be tilted too much onto the toe. If the hairline was greater than 30º, there would be a good chance that the back of the coffin bone was lower than the toe, putting excess pressure and strain on the back of the foot. These extreme cases appeared on few animals. Some upright hooves (toe at an angle >60°, high heels that can grow to the height of the toe (Łuszczyński et al. 2015) appeared. Pyrenean horses also presented average values between those ranges. Their hooves show proper alignment of the hoof to pastern axis and although the heel angle tends to be significantly higher than the front face angle it seems not to cause lameness signs.
A similar percentage of hoof disorders was detected in the front legs compared with the hind legs. The greater and differently directed forces to which a front leg hoof is exposed in comparison with hind legs not only determine differences in hoof and sole shape, but it can also make horses more prone to developing certain disorders in their front hooves. Due to differences in body proportions, the heavier a horse of a certain type or breed is, the greater the strain on the front legs (Łuszczyński et al. 2015) but probably the frequency of hoof failures can also be associated with other factors, e.g., the type of use of horses of certain breeds, as in this paper, similar front and hind hoof problems were detected in Pyrenean horses. It would not be the breed of horse, but the way it is used and system of management that determines the development of hoof derangements.
Łuszczyński et al. (Łuszczyński et al. 2015)) stablished that only 18.6%, 21.5% and 12.3% of Anglo-Arabians, Hucul and Silesian horses had hoof wall defects. In the present study, hoof problems were observed in more than one-half of the horses in the analysed population, but they did not imply clinical signs. Hoof defects detected in the Pyrenean horse are probably caused by inappropriate maintenance and feeding conditions, and harsh environmental conditions. Recent data have indicated that hoof shape and conformation is a by-product of genetics and the environment (Gordon et al. 2013). So, being sample formed by healthy individuals, detected angles among the Pyrenean horse must be considered natural for them, as due to genetics or to the environment. Hooves tended toward a less upright conformation as horse body condition increased. Such morphological adjustments may indicate variation in horn tubule orientation in response to greater structural loading.
It has also been suggested that the time of attainment of somatic maturity is another breed-related factor influencing susceptibility to hoof conformation faults and disorders (Łuszczyński et al. 2015). Hoof differences between foals and adults may result purely from differences in hoof shape. As our research is limited to the evaluation to the lateral aspect, further studies focused on other aspects (dorsal, solar) would add much information. Such studies will represent important considerations for hoof practitioners.
Further details
Conclusions
This methodical protocol seems to allow to better understand variations in structural angles, as well as alterations that are compatible with soundness. Using a systematic, methodical approach for every exam offers useful means of enhancing our ability to record small details that may otherwise be overlooked. Application of dogmas based on a rigid interpretation for assessing equine hoof conformation can be erroneous if they are applied with no distinction of the breed. It must be assumed that other static models which also optimise the dynamic efficiency of the foot and do not increase the risk of lameness exist. As a large range in hoof conformation dimensions exist in horses, new evaluation hoof model must take into account the influence of foot-type (front and hind feet), foot management (unshod versus shod), environmental conditions (domestic versus feral) on hoof morphology.
Conflict of interest statement
The author of this article did not have a financial or personal relationship with other people or organizations that could inappropriately influence or bias the content of the article.
Ethical compliance
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed for our research about hooves evaluation in the Pyrenean Catalan Horse. There has been no manipulation of animals. Research has also been done with healthy animals in grassland areas.
References
Barone, R. 1999. Anatomie Comparée Des Mamifères Domestiques. Tome 1. Ostéologie. 5e ed. Paris: Vigot Fréres.
Budras, K.D., W.O. Sack, and S. Röck. 2009. Anatomy of the Horse. 5th ed. Hannover: Schlütersche Verlagsgesellchaft mbH & Co.
Clayton, H.M. 1990. “The Effect of an Acute Hoof Wall Angulation on the Stride Kinematics of Trotting Horses.” Equine Veterinary Journal 22(9 S): 86–90.
Dyce, K.M., W.O. Sack, and C.J.G. Wensig. 1999. Anatomía Veterinaria. México: Manual Moderno.
Gordon, S. et al. 2013. “The Forelimb and Hoof Conformation in a Population of Mongolian Horses.” Journal of Equine Veterinary Science 33(2): 90–94. http://dx.doi.org/10.1016/j.jevs.2012.05.058.
Hammer, Ø., D.A.T. Harper, and P.D. Ryan. 2001. “PAST v. 2.17c.” Palaeontologia Electronica 4(1): 1–229.
Infante Gil, N. 2011. “Caracterización y Gestión de Los Recursos Genéticos de La Población Equina de Carne Del Pirineo Catalán (Cavall Pirinenc Català): Interrelacion Con Otras Razas Cárnicas Españolas.” Universitat Autònoma de Barcelona.
Leśniak, K. et al. 2019. “The Influence of Body Mass and Height on Equine Hoof Conformation and Symmetry.” Journal of Equine Veterinary Science 77: 43–49.
Łuszczyński, J. et al. 2015. “Frequency of Hoof Conformation Faults and Disorders in Horses of Several Breeds.” Turkish Journal of Veterinary and Animal Sciences 39(5): 594–99.
Nicolai, R.P.A. et al. 2017. “Radiographic Differences between Uneven Feet in Horses with Foot Lameness and Admitted for MRI Examination.” Journal of Equine Veterinary Science 54: 50–53.
Parés-Casanova, P.M. 2011. “A Nonlinear Model for Estimating Hoof Surface Area in Unshod Meat-Type Horses.” Journal of Equine Veterinary Science 31(7): 379–82.
Parés-Casanova, P.M., O.M. Samuel, and J. Pelegrín. 2016. “Weight Equality in Euthyroid Young Heavy Horses-a Postmortem Pilot Study.” Veterinarija ir Zootechnika 74(96).
Sellke, L., B. Patan-Zugaj, and K. Witter. 2020. “Nomenclature of Equine Hoof Measurements – a Systematic Literature Review.” Pferdeheilkunde Equine Medicine 36(3): 238–51.
Wilson, G.H. et al. 2009. “Skeletal Forelimb Measurements and Hoof Spread in Relation to Asymmetry in the Bilateral Forelimb of Horses.” Equine Veterinary
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