It is always a sad picture to see a „skin and bone“ horse. Horses can become malnourished because of various reasons – pure neglect, after a long and difficult illness, due to poor teeth quality, parasitism or poor quality food. Prolonged period of malnutrition leads to muscle wastage, general weakness, hypothermia, decreased gut function, wound healing, weather tolerance and immunity.
What happens to the horse’s body while starving?
The body first starts to metabolize glycogen (branched sugar) which is stored in liver and muscles. The glycogen storages are depleted within 24-36 hours and next in line to be digested is the fat. Once the body runs out of fat, it starts to digest its own protein (muscles). After 60-90 days the horse loses so much weight it might become unable to stand. The gut microbiom (friendly bacteria) decreases and enterocytes (gut cells) decrease their enzyme production. Therefore the ability to digest any incoming food will be decreased. Edema (soft watery swellings) of legs and lower chest might occur due to hypoalbuminemia (low blood protein).
What is the prognosis?
Poor prognosis for survival is given to horses which remain recumbent (unable to stand) for 3 days or more and if the weight loss is around 45-50%.
Refeeding Syndrome: the dangers of regaining access to food
During starvation the horse uses fat and protein to create energy. Once the access to food is renewed, every carbohydrate (sugar) intake causes a spike in insulin production. Insulin stimulates protein synthesis and transport of glucose and electrolytes to the cells. The shift of electrolytes causes decreased levels of phosphorus, mangesium and potassium. Possible results of these processes are neurological signs and even death due to cardiac and pulmonary failure. Sudden presence of carbohydrates in the gut may cause colic, diarrhea and laminitis.
How to refeed safely: Adaptation and Slow Weight Gain
The first 2-3 days (adaptation period) the horse should receive only 50% or less of the current energy requirements. Pellets and grain are to be avoided. Good quality hay should be fed in small portions every 4-6 hours and the horse should have access to minerals and vitamins. B-group vitamins are especially important, from which vitamin B1 can aid in refeeding syndrome prevention. Pro- and prebiotics should be fed (if the horse has reasonably healthy immune system) to repopulate the gut. The horse should be protected from weather conditions.
After the adaptation period the horse can be fed according to its current low body weight for another 2-3 days. Afterwards the horse should already be adapted to feed intake and the gut should be ready to take larger amounts of food, which can be slowly increased over 7-10 days according to the desired ideal body weight. Meals can be reduced to 2-3 times daily. At this stage it is normal for a mild diarrhea to occur, but it should resolve itself quickly without causing dehydration. Non-structural carbohydrates should cover less than 20% of the diet. Alfalfa can be slowly introduced as a good source of protein and minerals. Commonly the horse is then fed on completed pellets with low grain content or a senior feed. Additional protein source is needed to rebuild the muscles. Large amounts of oils should be avoided in the first 2 weeks, since the body lacks the enzymes to digest the fat. If the horse is strong enough, it can be turned out into paddock or a small pasture for 2-3 hours a day and slowly increase over time. Putting the horse with a group of younger and stronger horses is not recommended due to decreased ability to defend itself and therefore additional stress and risk of injuries.
Transition to normal weight:
In moderately starved horses it usually takes 60-90 days to regain weight and rebuild the muscles. In severely starved horses, however, it can take up to 6-10 months. The horse will need an extra care and attention over the whole period and a close cooperation with your veterinarian is essential = monitoring the blood profile, providing the needed dental and hoof care, parasite control and once the immune system is ready, the necessary vaccinations.
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