We will define malnourishment as horses in a condition of emaciated to very thin because of poor care.. This will include too little feed, feed of poor quality, and heavy parasitism. Unfortunately, malnourishment from improper care is a common scene with horses. Most often the reasons are not malicious but a combination of ignorance and economics. It would seem logical to think it is just a matter of restoring good care to fix the problem but there is a fairly high rate of mortality when trying to return an emaciated horse to good condition. The reasons for this are:
This article discusses the causes of malnourished horses and how to return these horses to good health. Included will be dealing with heavy parasitism and malnourished pregnant mares.
Sometimes history alone is enough to identify the probable cause of the malnourishment. A young horse with a clear history of no problems until becoming permanently stalled or placed into a paddock with only limited access to hay of poor quality needs little work to identify the probable cause of his emaciation. Still, a physical exam might reveal secondary problems or the severity of the condition and should be contemplated.
The history is not always so clear however. The horse may be older so at higher risk for Cushinoid Disease, teeth problems, or other chronic diseases. The horse may be at a sale barn and have no reliable history. In these cases the first step in dealing with any malnourished horse is a thorough physical exam, fecal, and laboratory evaluation. Teeth problems should be corrected immediately. If a mare, consider the possibility she may be pregnant.
Great care must be used in approaching de worming a horse that might be heavily parasitized. Whenever adult or larval stages of most parasites are killed, bleeding and inflammation is created in the wall of the bowel. Also, in the case of round worms or more rarely tapes, there is the potential for a physical obstruction when high numbers of this rather large parasite is present. A fecal flotation for parasite eggs should identify this condition and should have been part of a initial exam.
When this problem is identified or even just suspected, care should be used in the initial de worming to avoid a rapid kill off of large numbers of parasites. There is no concrete information on what is a safe way to do this and it would probably depend on a number of factors that include condition of the horse, age, type of parasites present, and number of parasites present. The following recommendation should work in most scenarios and is very cautious:
Signs of intolerance would include diarrhea, colic, black stools or blood in the stools, respiratory difficulties or weakness, within the next three days of deworming. Once treated and recovered from the reaction repeat the last step before going on.
A debilitated horse has a limited ability to respond to vaccines and may not tolerate a reaction that a healthy horse would have no problem with. Unless the horse is at immediate risk for contracting the disease, vaccines should wait until the horse is in an improving condition. An example of immediate risk might be a young horse with no vaccine history that has a full skin thickness wound particularly if deep, infected, or contaminated.
Abrupt refeeding of the starved horse can lead to death as a result of cardiac and respiratory failure in 3-5 days. During starvation, the body begins to use the tissues of the body as energy sources. The first is stored fat, followed by muscle tissue and eventually leads to a total body depletion of fat, protein, and electrolytes. The refeeding syndrome described in emaciated humans and thought to occur also in horses, is associated with the introduction of concentrated calories, primarily glucose, which stimulates the release of insulin and subsequently the influx of glucose and selected electrolytes into the cells. The result is severe hypophosphatemia, hypokalemia, and depletion of other phosphorylated metabolites, especially ADP and 2,3-diphosphoglycerate. The result is cell dysfunction. In horses this may be exhibited as increased susceptibility to infection including salmonella, cardiac dysfunction, nervous system dysfunction, and colic including a twisted bowel.
Doctors Christine L. Witham, DVM, MPVM and Carolyn L. Stull, MS, PhD studied the effects of different diets in starve horses and presented their findings in Refeeding the Starved Horse: Metabolic Responses to Three Isoenergetic Diets, 1997 AAEP PROCEEDINGS pg 347. Their findings are a bit surprising. They compared three diets: oat hay, oat hay and Equine Senior, and alfalfa hay alone. The alfalfa diet had the least deleterious effects on metabolic parameters that were measured. With that in mind, the following recommendations for beginning feeding the emaciated horse are made.
If the quality of the feed and hay is poor first, an attempt should be made to wean the horse over to better quality feed stuffs. Begin feeding the horse at either the current level of feeding or about 50% of normal feed rations depending whichever is greater. Best is to begin with a 50/50 mixture of good to excellent grass hay and alfalfa divided into six meals a day. To keep the calculations simple lets use the following definitions and guidelines. A normal ration is about 2.5% of the healthy body weight of the horse of good quality mixed hay. Do not use the emaciated weight for your calculations, instead estimate what the horse should weight and do your calculations from that figure. Let's do the calculations for a horse expected to weigh 1000 lbs. (450 kg) when healthy.
This should be fed for five days and if the horse is doing well increase the amount to 75% normal feed rations. You can go through all the calculations above and substitute 0.75 for the 0.50 in the calculations above. Much easier however is just do the proportionality calculation on the amount of each hay per feeding:
Again feed for five days and if well tolerated up the feed to 100% daily rations. Again the easy calculation is done with proportions:
Once the horse attains a thin condition (a 3 on our scale) he can go to three feedings daily but the total daily amount must be maintained. If the horses hay feedings are brought up to 2.5% of bodyweight but an ideal weight has not been attained concentrate can be added back to the diet slowly.
If the horse is going to be pastured on good quality grass, begin by following the above feeding regiment but instead of the grass hay substitute 10 minutes access for each pound of grass hay being allowed at the same frequencies suggested above. If the horse has trouble grazing due to teeth or other health problems, this time can be extended some but estimating the proper time may be difficult. Both vitamin and mineral supplementation, at normal levels, make good sense and can be added to the concentrate feedings. Water should be available free choice. During this program most horses will drop some weight the first week but should begin to gain thereafter.
As the horse becomes stronger and gains condition, the feedings can be combined and offered in fewer feedings. However the total amount of concentrate, not including the fat, should not exceed 1% of the expected normal weight and the amount per meal should be kept to below 4 lbs. concentrate per 1000 lbs. per feeding.
While a malnourished horse is recovering, it is best to not expose him to other horses. He is unable to compete with them for food and may be susceptible to coming down with infections that the other horses can resist. He will need extra protection from the elements and should have a run in shed at the least to be able to get out of the heat and cold. Blanketing during cold weather will help him conserve energy to build himself back up. If biting flies are bad, extra protection against them, particularly being brought in during the day, may be necessary as unlike a healthy horse he may not have the strength to persistently shoo them away.