Vol 34-6 April May 2013

FEEDING THE SICK OR INJURED HORSE

by Dr. Stephen Duren, Ph.D.
Hygain Feeds

The competition season is in full swing - the horse is fit and performing well. Then it happens, the horse takes a bad step and pulls up lame. The immediate concern is for the well-being of the horse, what is the nature of the injury, how severe is the injury and how much competition time will the horse miss? All logical questions, but another question to consider is how to feed this horse to speed up the recovery?

Lack of appetite
Injuries come in many forms. Bone fractures, skeletal lameness, muscle injuries, tendon injures, ligament injuries and a host of others. The net result of these injuries is that the horse immediately stops training and is often transported to a facility where it is confined to a stable for rest. Sickness or disease, much like injuries, can also result in lost competition and training time and stable rest.

The horse’s body responds to both injury and disease in a similar manner - the immediate visible response of the horse is a depressed appetite, which is usually the result of pain from injury or fever from disease. Lack of appetite and the body’s need for nutrients to heal often results in weight loss. This lack of appetite forces the body into a ‘catabolic’ state where the horse breaks down its own body tissues to provide energy. First the body will break down tissue stores of glycogen (sugar) and fat, but ultimately, the horse will break down protein from muscle and internal organs to fuel energy requirements. Visually the horse not only becomes thin, it may also lose muscle mass from the top-line and hindquarters. This tissue break down begins very soon after the injury or disease and persists until the injury or disease resolves. In a normal healthy horse, 90% of the calorie requirements come from fat stores within the body and another 5-8% comes from body protein. In an injured or sick horse, 50% of the calories come from fat stores, 20% from glycogen stores and 30% of the calories come from the breakdown of protein, muscle and internal organs. The immediate goal in feeding a sick or injured horse is to reverse the breakdown of body tissue.

The first step is to restore the horses’ appetite and this can be accomplished by medicating pain symptoms and resolving any infection that may be causing fever. Once the horse is willing to eat the specific nutrient requirements needed for the healing process can be addressed.

Nutrient requirements
Feeding horses that are sick or injured is not just a matter of providing hay and water. Sick or injured horses have elevated energy and protein requirements - the energy requirements for a 500kg sick or injured horse vary from 18 to 22 Mcal per day (measurement capability analysis). The protein requirements for a sick or injured horse are estimated to be 25% higher than a horse that is simply resting. Together, the nutrient requirements for energy and protein for a sick or injured horse are similar to the requirements of a healthy horse in light work, so what to do with an injured horse confined to a stall with elevated nutrient requirements, accustomed to daily exercise but not physically able to exercise? The horse must also be kept calm and quiet to prevent further injury. These challenges make feeding the sick or injured horse difficult.

ENERGY
Starting with the energy (calorie) needs of the injured or sick horse, the best way to provide calories without the horse bouncing off the walls with hyperactive behaviour needs to be ascertained. Begin by providing the horse with grass hay on a free-choice basis, as grass hay will provide calories in a slow release manner since it is fermented within the digestive tract. Furthermore, grass hay keeps the horse occupied as it takes hours to chew and consume the hay. In addition, a small amount (0.5% to 1% of body weight) of lucerne hay or pellets should also be fed. Lucerne contains more calories per kg compared to grass hay and it is a great source of quality protein and calcium, both of which are very important in the healing process. Soaked beet pulp can be fed to sick or injured horses as an additional source of calories. Beet pulp has the beneficial feature of providing digestible energy ranging between that of good quality hay and grains in the form of soluble fibre as opposed to sourcing energy from starches and sugars. Feeding soaked beet pulp instead of grains will minimise the sugar content of the diet and help control hyperactive behaviour.

Dietary fat in the form of rice bran oil is also a highly digestible, non-sugar energy source - it contains roughly three times as many digestible calories as any other feed ingredient with absolutely no sugar.
The energy (calorie) content of the diet is the only dietary factor that can be judged by looking at the horse. If the horse is provided with too many calories, it gains weight and eventually becomes fat, on the other hand, if enough calories are not fed the horse will lose weight and become thin. It is desirable for horses that are recovering from injury or disease to be in a healthy body condition, so that the ribs will not be visible, but can easily be felt when touching the horse. Horses that are thinner than that and whose ribs are visible will take longer to heal since they lack nutrient intake and body reserves.

Protein
Protein is a vital component of muscle, bone and most soft tissues, and it is an essential nutrient for the healing process as the protein requirements of a sick or injured horse are elevated by 25% over maintenance requirements. Protein is a component of most feed ingredients, with the exception of vegetable oil, and extra protein is most often supplied in the diet with lucerne hay, soybean meal or ground flax. Soybean meal is typically not fed as a single ingredient, but instead it is found in most grain concentrates and supplement pellets. Since feeds that contain grain also contain large amounts of sugar, which may cause erratic behaviour in horses, a low-intake, high protein supplement pellet is the best means of providing high quality soy protein to sick or injured horses.

The final component that must be addressed in the diet is the intake of vitamins and minerals as these function as building blocks for the repair of damaged tissue. They also aid the chemical reactions to synthesise or repair tissue within the body.Critical minerals and vitamins including calcium, phosphorus, copper, zinc, selenium, and vitamins A, D and E should be present in the diet.

It is obvious that the management of the horse is critical to the recovery process, a balanced diet for such a horse will include unlimited access to grass hay, lucerne hay/pellets, soaked beet pulp, rice bran oil and a low-intake, high protein supplement pellet.

The grain component of the diet has purposely been eliminated, or at least minimised, to control the sugar and starch intake of the horse. This should help to control some of the hyper behaviour often seen in horses confined to stables.

The final management component to help injured horses heal is to keep the horse active with in hand walking, grazing and light exercise as soon as the attending veterinarian gives approval. This exercise will help to stop muscle protein loss and will improve the attitude of sick or injured horses. In addition, any grazing the horse is allowed to do will provide a source of both energy and protein. So, should the horse suffer the unfortunate situation of becoming sick or injured, modify the diet as described to help the horse recover quickly.