European Association of Zoo- and Wildlife Veterinarians (EAZWV)

Determination of species-specific standard hoof measurements in captive wild ruminants: a practical approach to a common problem

S. Hammer¹, C. Hammer¹ and M. Clauss²

Â
Affiliation:

1.       Al Wabra Wildlife Preservation, P.O. Box 44069, Doha, State of Qatar; awwp.director@alwabra.com

2.       Institute of Animal Physiology, Physiological Chemistry and Animal Nutrition, Munich, Germany
Extended abstract

Overgrown hooves are a common problem in captive hoofstock collections (3). Usually, it is assumed that the causes of this problem are multifactorial, including genetics, enclosure substrate, and nutrition (1). Accordingly, prophylactic measures include controlled breeding, enclosure design and adequate dietary management; however, in practice, hoof-trimming has to be performed regularly in many species/institutions. On the one hand, the procedure should ideally be performed as fast as possible (to reduce the duration of either manual or chemical immobilization), but on the other hand, the zoo veterinarian faces the uncertainty of how much horn should be cut off. The hooves should be cut back as far as possible without violating the epidermal layer underneath. Without species-specific reference points, this procedure is usually performed by gradually removing layer after layer, using, according to deMaar and Ng’ang’a (2) “a mental image based on accumulated experience that blends normal domestic anatomy with wildlife anatomy”. These authors are, to our knowledge, the only ones who provide a range of reference measurements of the external hoof for several wild ungulates. Their approach is based on the assumption that the hoof shape of free-ranging animals represents the one to which hooves of captive specimens should be modeled. Unfortunately, this approach necessitates a representative sample of hooves from free-ranging animals. In our approach, we intended to work with material available from the captive stock in order to establish reference parameters. Therefore – because captive individuals often show abnormal hoof growth – internal rather than external anatomical measurements of the hoof were warranted. In domestic cattle, it has been demonstrated that parameters of the internal hoof are specific for a given breed (5); this supported an earlier claim that for adult individuals, one measure of length can be applied to all specimens of a given breed in hoof trimming (6). Consequently, our working hypothesis was that, for any given wild ruminant species, there are specific parameters of the internal hoof structure that can be used as reliable guidelines for the trimming of hooves of adult individuals.

In order to test this hypothesis, hooves of adult individuals each of three gazelle species (Soemmering’s gazelle, Gazella soemmeringii berberana, n=23; Pelzelns Gazelle, Gazella pelzeni, n=21; Spekes Gazelle, Gazella spekei, n=19) were collected during routine necropsy procedures at Al Wabra Wildlife Preservation (4) and stored frozen until analysis. Different techniques for the preparation of the hooves were tried. Both a cooking of the hooves in boiling water and sagittal sawing resulted in too much destruction of the corium to be of sufficient accuracy. Therefore, thawed hooves were carefully shortened with the aid of a grinder until the distal tip of the corium became visible. The distance between the coronary band and the distal tip of the epidermal toe was measured on the dorsal aspect of the toe (dorsal toe length) as well as the thickness of the dorsal hoof horn, using calipers. All measurements were taken by the same investigator.

Both the dorsal toe length and the thickness of the hoof horn were very uniform among individuals of a species. The average dorsal toe length was 31.4 mm, 22.3 mm and 22.0 mm for G. soemmeringii, G. pelzeni and G. spekei, respectively, with according standard deviations of 1.4 mm (range 25-34), 1.7 mm (19-26) and 1.5 (17-26) mm. There was no difference between the sexes, right or left legs, axial or abaxial hooves, nor between hooves with regular growth pattern or with hoof overgrowth; while there was no difference between front and hind hooves in G. soemeringii, the dorsal toe length of G. pelzeni and G. spekei was on average 1.9 mm and 0.8 mm longer on the hind hooves.

The results suggest that both the hoof wall thickness and the dorsal toe length are species-specific, genetically defined parameters of high inter-individual consistency. For the veterinary practice this means that these parameters can be used as reliable reference for fast, safe and efficient hoof-trimming procedures. Once a sufficient number of adult individuals of any given species has been used to determine the species-specific parameters, a yardstick for this species can be established (using the average dorsal toe length plus the hoof wall thickness plus a safety margin). For convenience, species-specific yardsticks can be made with plastic material. At Al Wabra Wildlife Preservation, the following three-step procedure is used in hoof trimming in adult individuals: 1. The optimal hoof length is determined by applying the yardstick to the hoof. 2. The hoof is shortened to the species-specific toe length with one cut. 3. The lateral hoof wall is adjusted by cutting it to one level with the sole.

We suggest that hooves of more captive ungulates should be used to establish according parameters for a wide range of species commonly kept in captivity. In species with a prominent sexual dimorphism, different values for males and females are to be expected. But even before such standard parameters are established, hoof trimming within a given collection can be made easier if the dorsal hoof length is documented after a successful hoof trim: this measure can be used as a reference for future trims in the same individual, and as a guideline in other individuals of the same species.

Â

References

1.     Clauss M and Kiefer B. Digestive acidosis in captive wild herbivores – implications for hoof health. Verh Ber Erkr Zootiere 2003; 41: 57-70.

2.     deMaar TW and Ng’ang’a MM. Normal hoof angles and other parameters of selected African ungulates. Proc AAZV and IAAAM Joint Conf 2000; 488-491.

3.     Fowler ME. Hoof, nail and claw problems in mammals. In: Fowler ME (ed) Zoo and Wild Animal Medicine, 2^nd ed. W.B. Saunders Co. Philadelphia, PE, 1986; 550-556.

4.     Hammer C, Hammer S. Al Wabra Wildlife Preservation – an introduction. International Zoo News, 2002; 49: 482-486.

5.     Sohrt JT. Determination of standard measurements for claw trimming by investigations of the relation between the internal anatomical structure and the horn capsule of claws from hind legs of German Black Pied cattle with considerations of laminitis lesions. Diss. Thesis, TiHo Hannover, 1999; 177 p [in German]

6.     Toussaint Raven E. Klauenpflege beim Rind. Über die Entstehung und die Vorbeuge von Sohlengeschwüren. Brouwer Uithof, Universiteit Utrecht, Netherlands, 1998; 136 p [in German]