12/01/2018
🙌‼️ Thankful to Fox Run Equine Center for sharing info with us on this very important topic!! 📣
Re-feeding Syndrome and Starvation of the Horse
By Brian S. Burks, D.V.M., Dipl. ABVP, Board-Certified in Equine Practice
Re-feeding syndrome encompasses the metabolic, electrolyte, and organ dysfunction that result from reintroduction of feed, especially carbohydrates, in the chronically malnourished patient. Derangements of multiple organs can occur, including the cardiovascular, respiratory, and neurologic systems. Untreated, or even treated, death may occur within the first week.
Horses typically consume 1.5-3.0% of body weight in forage per day. If additional calories are needed, concentrates can be fed, usually at no more than 1.5% of body weight per day, and often much less. So what happens when horses are chronically malnourished? Horses that have little to eat obviously lose weight, and may be in various states, having body scores that range from 1-3 on a scale of 1-9, with 1 being severely emaciated and 9 showing severe obesity. Most normal horses should be 5 of 9. When a malnourished horse comes into the care of a responsible party, the first step is to have the horse evaluated by an equine veterinarian. This will help to guide the re-feeding process, so that weight gain can be accomplished while mitigating complications that can occur during re-feeding.
The most common reasons for horses to be malnourished are ignorance and economic hardship. In some cases the party may be an animal hoarder, having more animals than any one person can reasonably provide food and basic attention to the individual horse. At minimum, each horse requires about 30 minutes per day to feed, water, and monitor for wounds, illness, or other malady.
Starving horses receive little or no food. They may suffer from various medical conditions including parasitism, poor dental care, and systemic illness such as pneumonia. Cold weather, pregnancy, and growth compound the situation.
Horses at risk for malnourishment and re-feeding syndrome include those with body condition scores below 3/9, those that have fasted longer than 5-10 days, those with 10% or greater weight loss over 60 days, and those with endocrine diseases. Ponies and miniature horses may have hepatic lipidosis and hyperlipemia; pregnant animals are also at risk for this disorder, and they may abort. They may have a pendulous or large abdomen, a head disproportionate to the body, no fat covering over bony protuberances, dull and shaggy coat that does not shed, depression, low hanging head, and lethargy. Subsequently, there may be colic, dysphagia and subsequent esophageal obstruction, weakness, inability to rise without assistance, and sterotypical behaviors such as cribbing and weaving.
Eating, especially carbohydrates, triggers the production of insulin, which is needed to send glucose into the cells of the body, but it also is responsible for some electrolyte movement into cells, most notably magnesium, potassium, and phosphorus, leaving a lack of them outside the cell, which can cause severe metabolic disorders and failure of the heart, lungs, and kidneys. In severe cases, the brain will become affected. Horses with normal stores of the electrolytes and other minerals are equipped to handle changes; starved horses do not have body stores of minerals, and cannot respond appropriately. These animals are whole body deficient (blood and tissues) in sodium, potassium, and especially phosphorus. They are also often hypocalcemic and hypomagnesemic. Anemia is common and stems from parasitism, hypophosphatemia, and a lack of iron and copper.
Signs of re-feeding syndrome include increased weakness, neurologic dysfunction, irritability, and aggression. There may be cardiac arrhythmias and congestive heart failure. Peripheral edema may also be present. There is also muscle wasting and fat atrophy. Coma and death may follow. Any of these signs warrants immediate evaluation by an equine veterinarian who can monitor fluid and electrolyte shifts, correcting imbalances via intravenous fluids and electrolytes. Decubital ulcers occur in animals that are down, and unable to rise, due to the prominence of bony protuberances.
When the animal is starving, the body indiscriminately uses tissues to survive, breaking down protein and fat. This may lead to long-term consequences when the heart or kidneys become damaged. In contrast, well fed horses have a fat and carbohydrates in their diet, providing calories. The body will build stores that are used when the horse lives, works, plays, and sleeps.
Re-feeding the horse thus requires a slow and steady provision of food in order to avoid overwhelming the impaired digestive tract and metabolic system. Long periods of starvation affect the lining of the GIT, leading to impaired absorption of nutrients and water. There is also an increased risk of sepsis, as bacteria are more likely to enter the blood stream as they translocate across the intestinal wall and because hyperglycemia inhibits white blood cell (neutrophil) function.
Once a horse loses 50% of its body weight, the prognosis for survival is poor. Those that become recumbent and unable to rise or even stand without assistance, and the use of a sling may be warranted.
Dehydration is common in neglected horses. If water is suddenly allowed, this may cause sudden and severe shifts of fluid into the cells, which is inappropriate and can cause permanent damage. This is because there are more electrolytes within the cell, compared to plasma. Salt toxicity (a relative term- not actually excessive salt intake) is common; this is where mammals have lost water, and the cell then takes up sodium (salt) as its concentration is higher in plasma. Then, when water is offered, the sodium gets pulled back out of the cell, as now the plasma concentration is too low. This changing of cell size is especially important for the brain cells; seizures and other neurologic symptoms may ensue. Thus offering small amounts of water frequently may be warranted. Once thirst has been sated, then the horse can be allowed free choice water. In some cases, intravenous fluids may be necessary, while in others a diluted electrolyte solution may need to be provided via nasogastric intubation.
For the first 7-14 days, no grain or other supplement should be provided. Small amounts of alfalfa hay is ideal. Grass hay may be substituted. Some horses may not be able to masticate properly, due to muscle loss, and soaked alfalfa pellets may be used. Triple Crown Senior is a complete feed that also works very well. Again, small meals are given frequently. Once the animal has stabilized, then deworming may commence, and the teeth may be floated and other dental problems corrected.
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