Importance of Vitamin E for Horses

Vitamin E has numerous functions in the body, many of which are still not completely understood. Vitamin E is essential for the integrity and optimum function of reproductive, muscular, circulatory, nervous, and immune systems.

Its action as a natural antioxidant is seen as the underlying factor of most vitamin E functions. Vitamin E is considered to be the most effective natural lipid-soluble chain-breaking antioxidant. The action of vitamin E is very important in cell membranes, protecting them from peroxidative damage. This is especially important in the mitochondrial membrane, where enzymes involved in respiratory chain energy production are located. Selenium, like vitamin E, also acts to prevent lipid peroxidation, but with differing mechanisms. The two complement each other, one appearing to be able to compensate for the absence of the other to a certain extent. Signs of vitamin E deficiency, such as nutritional muscular dystrophy, are often the same as those seen with selenium deficiency. Other diseases associated with low serum vitamin E include degenerative myelopathy and degenerative myeloencephalopathy.

There are at least eight forms of vitamin E found widely distributed in nature: four tocopherols and four tocotrienols. The majority of vitamin E activity in animal tissues is generally assumed to be alpha-tocopherol and when it is present it is used preferentially. Tocopherols are extremely resistant to heat but readily oxidized. Natural vitamin E is subject to destruction by oxidation, a process that is accelerated by heat, moisture, rancid fat, and certain trace minerals. Horses have the capability to store much less vitamin E than vitamin A. However, stores are thought to be able to compensate for about four months or more of inadequate vitamin E intake.

Vitamin E is abundant in green growing pastures, particularly in alfalfa (lucerne). The content diminishes with maturation, especially after the plants go to seed. Harvesting the forage diminishes the quantity of vitamin E present, and storage of the hay further decreases the amount of vitamin A by as much as 50% in the first month. Vitamin E is abundant in the germ of grains and oils pressed from the germ. Vegetable oils such as corn and soybean oil are relatively high in vitamin E. In practice, the vitamin E content of other feedstuffs is variable and not readily predictable because of handling and storage time. Therefore, it is common practice to supplement animal feeds with vitamin E. Since esterification stabilizes vitamin E, commercial supplements usually contain tocopheryl acetates.

Vitamin E appears to be the most researched vitamin at this time in production animals. Several studies have reported evidence of oxidative stress occurring with exercise in both humans and rodents. Since the main function of vitamin E is to protect the cell against peroxidative damage, lipid peroxidation as a result of exercise may be influenced by the concentration of vitamin E present in the diet. Signs of vitamin E toxicity in the horse have not been produced.

Back Pain in Horses

Wringing the tail, throwing the head, jigging, bolting, not standing still to be tacked up or mounted, refusing to pick up a lead or a gait…these are only a few of the behaviors horses might show when they have back pain. Some of these signs are more subtle than others, and they may come and go over the course of time, making it difficult for owners to pinpoint what is causing them. A veterinarian can often diagnose back pain in a horse, but in some cases, even a professional may have trouble telling just where the horse’s pain is.

Back pain in horses can be caused by a number of factors includingarthritis, malformed vertebrae, injuries, overwork, or a training program that asks for a higher level of performance than the horse has been prepared for. Horses that develop back pain from being ridden may have strained some of the muscles that help to move and stabilize the back. When pain and inflammation restrict the action of these muscles, the job of stabilizing the back falls to other muscle groups that are less able to perform this function.

In horses, the longissimus and iliocostalis muscles lie parallel to the spine for the entire length of the back. These muscles function to flex the horse’s back in both horizontal and vertical planes. The multifidus muscles form a deeper layer and instead of influencing the whole back, each one of these shorter muscles controls only a few vertebrae and the joints between them. When pain occurs, the multifidus muscles fail to stabilize the intervertebral joints as efficiently as they should, and they tend not to recover full function even after the pain has been relieved. Over the course of time, instability increases the horse’s risk for developing arthritis in these joints.

A veterinarian should always perform an examination of a horse that shows signs of back pain. Because back pain can be indicated by a range of behaviors, owners should consider the possibility that back pain might be a cause of resistance, other training problems, or lameness elsewhere, such as the hocks. Ruling out this factor may clarify training decisions such as whether to give the horse a break or try a different approach to teaching a new skill.

Humans recovering from back injury have benefited from physical therapy aimed at reactivating muscles that stabilize the vertebrae. Hilary Clayton, a professor in the equine sports medicine department at Michigan State University, has conducted research that shows the same effect can be achieved in horses. If the examining veterinarian feels that stretching exercises would help a horse build or regain strength and flexibility in its back muscles, the owner can incorporate these exercises into the daily schedule. Commonly known as “carrot stretches,” the activities involve the owner holding a carrot or other enticing treat just out of reach to encourage the horse to stretch its neck and back both lengthwise and laterally. Beginning exercises should ask for just a little bend or stretch to be held for a few seconds before allowing the horse to reach the treat (wear gloves to protect fingers from enthusiastic carrot eaters!). Each session should ask for a small increase of effort.