REFEEDING SYNDROME - why you need to be careful feeding starving animals

When you see an emaciated animal, the first thing you want to do is feed it as much as much as you can. But, this is actually SUPER DANGEROUS for the animal. Let me explain why…


When an animal is starved, this causes a drop in blood sugar levels. The body responds by releasing hormones to use up the stored sugars (glucose) and to convert fats (triglycerides)/ body proteins to glucose to try to maintain blood sugar levels. The body prefers to use carbohydrates as its main fuel source but in periods of starvation, it begins to use fat (lipids) sources. The body adapts to the decreased caloric intake and depletes the lean body mass and the bodies electrolytes.


When the starved animal gets fed a whole bunch of food, there is an abrupt shift for the body to use carbohydrates as the primary fuel source again! But, the carbohydrate results in the body releases insulin. The hormone insulin does more than just allows glucose into cells. It also can drive other molecules and electrolytes into the cells. This causes a HUGE disruptions in the bodies electrolytes (magnesium and potassium) and fluid balance. It also initiates glucose storage pathways that require phosphorus for energy (ATP). This can cause a profound drop in phosphorus levels.


Having too low or too high of certain electrolytes can have catastrophic effects on the body. What can happen with…

- Low Potassium (hypokalemia): severe muscles weakness, arrhythmias, slow intestinal movement (ileus)

- Low phosphorus (hypophosphatemia): rupture of red blood cells (hemolytic anemia), muscle weakness, muscle breakdown (rhabdomyolysis), kidney damage, heart dysfunction

- Low magnesium (hypomagnesemia): heart arrhythmias, muscle weakness, inappetence, abdominal pain, low potassium and calcium


Therapy consists of trying to get the blood electrolytes back to normal with IV supplementation and close monitoring of the blood. Along with this, we need to SLOWLY re-introduce food to the animal in small amounts over 5-10 days.

This is what happened to Ethel the ear infection dog. She was found locked in a kennel in an abandoned house. After starving for several days, the people that found her fed her a whole bunch of kibble. Unfortunately, this gave her re-feeding syndrome. When she presented to me, she was jaundice and mildly anemic. This was because her red blood cells were rupturing because of the electrolyte imbalance.

IF YOU SEE A STARVING ANIMAL… DO NOT feed them as much as they will eat. This is super dangerous and can kill the animal. The animals resting energy requirement (RER) calories needs to be calculated and then the animal is fed ~20-25% of this amount to start. The amount of calories fed is slowly increased over 5-10 days so the body has time to adjust to food again.

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