Anyone who has spent time around horses is familiar with scars. Horses have a knack for injuring themselves, and scars are the inevitable consequence. Scars can be a problem for show horses, whose good appearance is of the utmost importance. They can also make any horse less desirable to buyers simply for aesthetic reasons. Scars also leave the affected area prone to reinjury, since the scar is not as strong as normal skin.
As unfortunate as they are, scars happen for good reason. They are the results of the body’s healing process, which serves to close up a wound and prevent it from becoming infected.
How Scars Form
To understand how scars develop on a horse’s body, it’s important to take a look at the healing process and how it works.
“If a deep enough wound is allowed to heal on its own—without sutures—it is called ‘healing by second intention’ and involves granulation and contraction of tissues,” says veterinarian Heidi P. Watkins, DVM, of Norco, Calif. “There are four phases of any healing that occur from the moment an injury happens. The first two stages are the inflammatory phase, where blood vessels constrict, blood coagulates, and fibrin and plasma glue wound edges; and the debridement phase, where inflammatory cells migrate into the wound and nutrients are brought into the wound by adjacent tissue.” These two phases occur within the first three to five days after injury. At this point a scab—dead, dry skin and inflammatory cells—usually appears at the site of the wound.
The next two phases are the repair phase and the maturation phase, according to Dr. Watkins. “During the repair phase, fibroblasts, which are the basic cells of connective tissue, appear in the wound bed and synthesize new collagen to fill in and add tensile strength to the wound,” she says. “This phase occurs at about two to four days after injury. During the maturation phase, the excess collagen that was laid down is resorbed and remodeled, which begins about two or three weeks to six months or more after injury. This final stage forms the scar, which has only about 80 percent of the strength of the pre-injury tissue.”
The Trouble With Scars
Although scars are the normal result of the body’s healing process, they cause problems for horse owners for various reasons.
“Some of the biggest problems with scar tissue formation in the horse occurs when the scars appear on the surface of the body,” says Dr. Watkins. “These scars can affect the appearance of the horse. Also, because scar tissue is not as strong as the original tissue, there can be problems with reinjury in areas of high skin tension, like on the lower limbs.”
A common problem in horses that have injured themselves is the development of proud flesh, which is the term horsemen use to describe excessive granulation tissue that builds up at the wound site.
According to Dr. Watkins, granulation tissue is made up of numerous newly formed small blood vessels and connective tissue on the healing surface of the wound. Excessive granulation is an exaggerated response from the horse’s body, combined with a lack of skin coverage.