Camelids’ Unique Gait & Foot Structure. By Sue Alt DVM and David E Anderson DVM, MS, DACVS, College of Veterinary Medicine, Kansas State University. Photos courtesy of Dr. David Anderson, Eric Lorince & Chris Barty.
Have you ever watched a llama or an alpaca walk? They are fascinating creatures. Although these camelids are ruminating species, they do not have hooves. Horses, cattle, sheep, goats, even pigs have hooves – but not llamas and alpacas. Why is that? Llamas and alpacas have a padded covering to the bottom of the foot and a toenail on the end. This is unique among ruminating species. This article may help you understand why foot maintenance and toenail trimming are vital components to your routine herd health program.
TAXONOMY AND ANATOMY
Camelids and ruminants are both in the order Artiodactyla and South American camelids belong within the suborder Tylopoda – which is Latin for padded foot. The padded foot minimises damage to the terrain and, in the case of llamas only, is ideal for use in hiking and packing. There are two digits or toes on each camelid foot (Figure 1). Three small bones, or phalangeas, make up the skeleton of the foot (Figure 2). The first phalanx (P1) is connected to the fetlock and the second and third phalanx (P2 and P3) are lower down on the limb and are horizontal to the ground. The splayed toes increase stability and sure-footedness. The thick pad is comparable to that of dogs.
The surface that touches the ground is a soft, cornified layer of epithelium and is called the sole or slipper (Figure 3). There is a separate slipper for each digit and these are conjoined at the heel of the foot (Figure 4). Deep to the slipper is the corium, a fibrous sheath consisting of connective tissue, containing blood vessels and nerves. The digital cushion or “padded foot” of camelids is interspersed between the slipper, the corium, and P2 and P3.
The cushion is made up of collagenous and elastic fibers interspersed with masses of fat and cartilage. The small non-weight bearing nail is located at the extremity of the digit, is similar to a dog’s toenail, and is closely attached to P3 via the corium. The foot is joined to the leg at the fetlock joint. The camelid stance is referred to as modified digitigrade (Figure 5), similar to dogs and cats, with locomotion on the digits (both the middle and the last phalanx contact the ground). Conversely, true ruminants and horses are unguligrade, walking on the tips of their toes (only the last phalanx contacts the ground; [Figure 6]).