Page 298 - Anatomy and Physiology of Farm Animals, 8th Edition

The Integument / 283

Dehorning or disbudding can be hocks. The chestnuts are thought to be
vestigial metacarpal and metatarsal foot-
VetBooks.ir accomplished by destroying the corium pads. They are variably developed, being
when only buttons (the small cutaneous
small (or even absent on the hindlimbs) in
primordium of the future horn) are pre-
sent in the young animal (usually less some individuals, or prominent in others.
than 8 weeks for cattle). This is most Ergots are small projections of cornified
typically done by surgical removal of the epithelium in the center of the palmar
button or by its destruction with a hot (plantar) part of the fetlock of the horse.
iron or with caustic material. For The tuft of hair at the fetlock hides the
humane reasons, veterinarians adminis- ergot in most instances (Fig. 14‐9).
ter a local anesthetic block of the cor-
nual nerve before dehorning. After the
horn has started to develop, the entire Coat Color in Horses
corium and cornual process must be
removed along with the horn epidermis The description of equine coat color can
and a small amount of adjacent skin to vary with the breed or the part of the coun-
ensure complete dehorning. If any parts try. The following guidelines are provided
are left, an irregular horn stub (a scur) to familiarize you with some of the more
may develop. Dehorning after 3 or 4 common colors and the terms used to
months of age risks opening the frontal describe them, but it should be understood
sinus to the outside, as the cornual that legitimate disagreements will arise
diverticulum enlarges into the bony core between knowledgeable equestrians.
of the horn as the animal matures. The color of hair (and skin) arises
through the combination of melanins and
Dewclaws lipofuscins. These proteins are associated
with various tones of black, brown, and
red. Their concentration and distribution
The accessory digits, commonly known as determine the coat color. Most solid colors
dewclaws, of ruminants correspond to (no spots) are derived from variations on
digits II (medial) and V (lateral) (Figs. 14‐6 and dilutions of black, bay, gray, and
and 14‐7). Ruminant dewclaws lack well‐ chestnut.
developed phalanges; their hoofs have a True black horses are rare except in a
wall and small bulb. Ruminant dewclaws few breeds (e.g., Shire and Percheron). The
do not bear weight and as a rule have little body hairs and all the points are completely
clinical significance. Dairy farmers occa- black without brown or white hair inter-
sionally have the medial dewclaws on the mixed. Black coats frequently bleach with
pelvic limbs removed as a prophylactic prolonged exposure to sunlight, rendering
measure against injury to the udder by them less deeply black.
these horny growths. The dewclaws of The bay horse’s body color ranges from
pigs, like the weight‐bearing digits, have tan through red to reddish‐brown. The
three phalanges and a smaller but well‐ points (mane, tail, lower limbs, and ear
developed hoof. Porcine dewclaws occa- rims) are black; the black limbs may not be
sionally make contact with the ground apparent on individuals with extensive
when the pig stands on soft surfaces.
white markings. Many adjectives can be
added to the basic term “bay,” but fortu-
Chestnuts and Ergots nately most of them are self‐explanatory.
Blood bay, red bay, mahogany bay, and
Chestnuts are hornlike growths on the sandy bay are just some examples of these
medial sides of horses’ limbs. The front terms. Very dark bays (sometimes called
chestnuts are proximal to the carpus, and black bay or mahogany bay) are described
the hind chestnuts are slightly distal to the as brown in some registries (notably the