By Carolyn Stull, MS, PhD

It is difficult to comprehend the long-term neglect and surrounding situations that produce such a devastated, depressed creature as a starved horse. The bones are so prominent that the skeleton appears to belong to a larger horse, the head is disproportionately large compared with the body, and the tail is always low and motionless.

But the low hanging head tells it all. The ears barely move to any sounds in the environment, no extra energy is spent interacting with herd mates. The eyes are dull, without expression, without expectations.

Malnourished and poorly cared for horses can be found even in countries of relative wealth such as Canada and the United States. In fact, the problem of neglected horses in these countries has worsened in recent years and reflects the growing number of horses that are no longer wanted or needed, or whose owners are no longer capable of providing care for them, physically or financially. The degree of worsening could be related to both the global recession that has created economic hardship for many horse owners, and the simultaneous closure of U.S. equine slaughter facilities in 2007. During the previous decade, these slaughter plants had processed approximately 68,000 horses per year.

It is estimated that approximately 100,000 horses per year in the United States alone are categorized as “unwanted.” Unwanted horses range from being normal, healthy horses of varying ages and breeds, to horses with some type of disability or infirmity, horses that are unattractive, horses that fail to meet their owner’s expectations for their intended use (e.g. athletic ability), horses with non-life-threatening diseases, horses with behavioural problems, or horses that are dangerous.

A relatively small number of these horses end up in a rescue or sanctuary facility where they can be rehabilitated and rehomed. As might be expected for horses that are relinquished to non-profit facilities, poor body condition is apparent in many of the horses, with a number of them considered emaciated, very thin, or thin.

In humans suffering from starvation caused by illnesses such as anorexia, cancer, or gastrointestinal obstruction, patients can develop “refeeding syndrome” when they are given concentrated calories, which in turn can lead to heart, respiratory, and kidney failure three to five days after the initial meal. This same syndrome has been reported in the literature for horses. Thus, University of California, Davis (UC Davis), researchers have developed a refeeding program for horses that would minimize these effects and enable the horse to gradually return to normal body weight.

Like humans, horses that are severely malnourished can develop “refeeding syndrome” when they are given concentrated calories, which can lead to heart, respiratory, and kidney failure about three to five days after the initial meal. - Photo: George Donnelly/Wikimedia Commons.

What Happens During Starvation

During the starvation process, the horse initially uses any fat and carbohydrate stores in his body to supply energy for metabolism. This is the normal process for any healthy horse: fat and carbohydrates are used for energy, exercise, brain function, circulation, etc. and are then replaced with nutrients from food. The cycle is constant and never-ending, even during sleep. In a starved animal, once this source of fat and carbohydrates is gone, energy is derived from the breakdown of protein.

While protein is a component of every tissue, there are no inert stores of it in the body such as there are for fat and carbohydrates. Consequently, the starved body uses protein not only from the muscles, but also from vital tissues such as the heart and even gastrointestinal tissues – tissue that is necessary for life. The starved body cannot select which tissue protein will be metabolized for energy. As time goes by, the horse’s survival is in a precarious situation. When a horse loses more than 50 percent of its body weight, the prognosis for survival is extremely poor.

Experimental Diets for Refeeding

In a study on the effects of different types of feed used for refeeding starved horses, we selected three that were very different in nutrient composition: alfalfa hay, oat hay, and a commercially available complete feed consisting of grain, molasses, fat, and alfalfa. Alfalfa hay is known to be high in protein (20 percent) but low in the carbohydrate starch (3 percent). Oat hay is high in fibre but low in protein (7 percent). The complete feed represented a feed high in carbohydrate concentration with 19 percent starch.

The three types of feed were given to 22 starved horses that were brought to the UC Davis research site as representative of horses rescued by equine organizations. Horses were fed one of the three diets over a ten day rehabilitation period. The researchers focused on this time period as critical to successfully transitioning the gut from a starved state to a fed state. Even though the diets were different in composition, they were fed in amounts that were equivalent on a caloric basis so that horses assigned the oat hay diet, for example, received the largest volume of feed, while the horses on the complete feed received the smallest amount but the same number of calories at each meal.

Which Diet Worked Best?

Our results with the complete feed were very consistent with human studies conducted years earlier using concentrated calories. As the horse ate the high carbohydrate diet, insulin was released in response to the high level of starch. The job of the hormone insulin is to facilitate carbohydrate uptake from the bloodstream and storage in cells for future energy use, but it also simultaneously draws the electrolytes phosphorus and magnesium from circulation into the cells. Since the starved horse has no stores of electrolytes, this depletion can lead to kidney, heart, and respiratory failure. These effects do not occur with the initial meal but can be seen several days to a week later due to the repetition of insulin release following a high carbohydrate meal and the cumulative depletion of electrolytes.

The oat hay diet was very bulky and caused diarrhea in several horses. Several essential nutrients such as phosphorus and magnesium were low in the oat hay compared with the other diets, so this diet did not support a successful rehabilitation.

The alfalfa hay had the best results due to its high composition of quality protein, but also the major electrolytes phosphorus and magnesium. Since alfalfa hay is very low in carbohydrate content, there were minimal effects due to insulin response.

In a subsequent feeding study, we compared a ration of alfalfa hay to a ration of alfalfa hay and corn oil. Equine diets usually do not contain much fat, but in the recent decade, the use of corn oil to increase the energy density of a meal has been widely used in nutrition programs for older horses and in horses undergoing intensive training programs. The two diets were fed again on an equal-calorie basis.

Although the corn oil had no harmful effects, substituting calories from corn oil for alfalfa decreased the total nutrient content of phosphorus and magnesium in the diet. Thus, the response to the diet combining corn oil and alfalfa showed a decreasing blood phosphorus level over the ten day period, which was not advantageous to rehabilitation. Again, the alfalfa diet was the most effective at delivering the necessary nutrients in the correct amounts to the starved horse.

Our research has shown that starved horses had very different responses to several diets. We found that the best approach for initial refeeding of the starved horse consists of frequent, small amounts of high quality alfalfa. High quality alfalfa has characteristics of leafiness, fine stems, no dust or mold, with a crude protein content of 16 to more than 20 percent. This amount should be increased slowly at each meal and the number of feedings decreased gradually over ten days. After ten days to two weeks, horses can be fed as much as they will eat.

The horse will show signs of increased energy after about two weeks. Ear, eye, and head movement will be the first noticeable improvements. Some weight gain can be achieved in one month, but three to five months usually are needed to rehabilitate the starved horse back to a normal body weight. Veterinary care and nutritional advice should be sought during the rehabilitation as complications can arise.

Some weight gain can be achieved in one month, but usually three to five months are needed to rehabilitate the starved horse back to a normal body weight. - Photo: JD Lamb/Flickr

Recommendations for Refeeding a Starved Horse

Note: A scale is essential for weighing the hay in the initial steps of refeeding.

Days 1-3: Feed one pound (approximately one-sixth of a flake) of high-quality alfalfa every four hours (total of six pounds per day in six feedings). Contact a veterinarian to evaluate the medical status of the horse.

Days 4-10: Slowly increase the amount of alfalfa and decrease the number of feedings so that by Day 6 you are feeding just over four pounds of hay every eight hours (total of 13 pounds per day in three feedings).

Day 10 and for several months: Feed as much alfalfa as the horse will eat and decrease feeding to twice a day. Provide access to a salt block. Do not feed grain, treats such as apples or carrots, or other supplements until the horse is well along in its recovery. Each feeding of grain, treats, or any supplements complicates the return of normal metabolic function and can result in death.

Provide clean, fresh water at all times.

Deworming and correction of dental problems are very beneficial to the horse's recovery.

Other types of hay such as grass hay may be added following the first two weeks of refeeding, but these should be added slowly over time. Alfalfa hay contains adequate amounts of salt for a sedentary horse, so use caution in offering a salt block within the first four to six weeks.

This article was reprinted from The Horse Report (July 2012) with permission from the Center for Equine Health, School of Veterinary Medicine, University of California, Davis.

Main Photo: During the starvation process, the horse initially uses any fat and carbohydrate stores in his body to supply energy for metabolism. When these stores become depleted, the starved horse’s body derives energy from the breakdown of protein not only from his muscles, but also from vital tissues such as the heart and gastrointestinal tissues. Photo: ©CanStockPhoto.com/Imagex.