Common Diseases of Farm Animals

by Robert Alexander Craig

The predisposing causes are faulty conformation that favors pressure from the shoe on the sole between the bars and wall and weak heels. Corns are commonly met with in feet having contracted quarters. The principal external causes are wrong methods of shoeing and allowing the shoes to remain on the feet for too long a period.

A common symptom of corns is lameness. In order to relieve the pressure over the inflamed part, the animal stands with the foot slightly flexed at the fetlock. The lameness is not characteristic. It is only by a local examination of the foot, made by pressing on the sole or cutting away the horn, that we are able to form a positive diagnosis.

We describe the diseased changes by using the terms dry, moist and suppurative corns. In the dry corn we find the horn stained and infiltrated with blood. In the moist corn the hoof may be colored the same as in the former, but in addition there is a space between the vascular and horny tissue that is filled with a serous-like fluid. If this collection of fluid becomes infected with pus organisms and is changed to pus, it is then termed a suppurative corn. Sometimes the pus pushes its way upward and backward between the sensitive laminae and the wall, and makes its appearance at the margin of the coronary band in the region of the quarters or heels. This usually occurs when the tissues beneath the horny frog become bruised or the sensitive tissue pricked by a nail. It is commonly termed "gravelled." Pus rarely breaks through the thick horny tissue, but follows the wall and breaks through the skin where it meets with the least resistance. Corns may be considered a serious unsoundness in driving horses.

The treatment is largely preventive. Trimming the foot and fitting the shoe properly are important preventive measures. The practice of cutting away the bars and sole or "opening up the heels," as it is commonly termed, should be condemned. This method of trimming the foot instead of preventing corns is a very common factor in producing them. The shoe should not be too short or too narrow. It should follow the outline of the wall and rest evenly on its bearing margin. If this is practised, weakening the wall by cutting off that portion allowed to project beyond the shoe is unnecessary. Feet that have low heels and large, prominent frogs should be shod with shoes thick at the heels. The best line of treatment for a horse that is subject to corns is to remove the shoes and allow the animal to run in a pasture. If this is impossible, poulticing the feet or standing the animal in moist clay will help in relieving the soreness. Excessive cutting away of the horny sole is contra-indicated. Suppurative corns should be given proper drainage and treatment.

LAMINITIS, "FOUNDER."—This is an inflammation of the sensitive or vascular stricture of the foot. The inflammation may be acute, subacute or chronic. Stockmen frequently use a classification for laminitis based on the causes. Feed, road and water founder are common terms used in speaking of this disease. The inflammation is usually limited to the front feet.

The causes of laminitis are overfeeding, sudden changes in the feed, drinking a large quantity of water when the animal is overheated, overexertion, exhaustion and chilling of the body by standing the animal in a cold draft. It may be associated with such diseases as rheumatism, influenza and colic.

The symptoms vary in the different forms of the disease. Pain is the most characteristic symptom. The sensitive or vascular structure of the foot has an abundant supply of sensory nerves, and, as it is situated between the hoof and the bony core, the pressure and pain resulting from the inflammation are severe.

In the acute form general symptoms are manifested. The appetite is impaired, the body temperature elevated and the pulse beats and respirations quickened. If the inflammation is severe, the animal prefers to lie down. This is especially true if all four feet are inflamed. In most cases the horse stands with the forefeet well forward and the hind feet in front of their normal position and under the body. The affected feet are feverish and very sensitive to jarring or pressure. Moving about increases the pain in the feet, and it may be very difficult to make the animal step about the stall.

In the subacute form the symptoms are less severe. The irregularity in the gait is especially noticeable when the animal is turned quickly. The local symptoms are less marked than in the acute form and the general symptoms may be absent.

The chronic form is characterized by changes in the shape and appearance of the hoofs (Fig. 43). The wall shows prominent ridges or rings, the toe may be concave, thick and long and the sole less arched than usual, or convex. The degree of lameness varies. It is more noticeable when the horse is moved over a hard roadway than if moved over soft ground. One attack of laminitis may predispose the animal to a second attack.