Feeding Skinny Animals:  Helpful or Harmful?

By Laura Nelson, Dane County Humane Society Extern

What is refeeding syndrome?

Refeeding syndrome is an uncommon problem seen in general practice, but becomes much more of a reality in the shelter environment.  It occurs when a starving animal becomes fed too generously, often out of sympathy for the animal's condition (abuse, neglect, or abandonment).  While a good-hearted act, it can prove disastrous for the animal, as consequential metabolic alterations occur as a result. 

When are animals affected?

• When they have a body condition score less than 3.5/9.
  
• When they have fasted for more than 5-10 days even if they are of normal body condition.
  
• Animals who have lost more than 10% body weight in less than two months.
  
• Animals with hepatic lipidosis (fatty liver), diabetic ketoacidosis, or Cushing's disease (hyperadrenocorticism).
  
• Animals that are lactating, growing, or are in gestation are more susceptible.
  
• Cats may be more susceptible than dogs due to decreased energy stores.

What happens during starvation?

Starvation causes carbohydrate, fat, and protein stores to become depleted.   Skeletal muscle becomes utilized for energy, and muscle wasting occurs as a result. The body begins to produce ketones (acids produced by the body that can be fatal in high amounts), insulin secretion decreases, and a decrease in metabolic rate occurs.  Starvation also causes potassium, magnesium, and phosphorus electrolytes to become depleted.  This can be very important because these electrolytes are necessary for vital body functions.

What happens during refeeding syndrome?

When animals are fed after a period of starvation, the body is able to again utilize glucose for energy, which it wasn’t able to do during starvation because glucose was depleted. Glucose needs phosphorus to generate energy for the body, so it continues to draw from the already decreased amount, making the levels of phosphorus even lower. This decrease in phosphorus level leads to the most severe effects of refeeding syndrome. 

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What are the effects of low phosphorus levels?

The main effect of decreased phosphorus is hemolytic anemia.  Phosphorus is needed for red blood cells in the body to maintain their shape, so lack of phosphorus causes disrupts the integrity of the red blood cells and causes them to burst. Because red blood cells are responsible for delivering oxygen to tissues in the body, loss of red blood cells causes lack of oxygen delivery. This can lead to weakness, lethargy, neurological symptoms, and death.

What can happen from decreased potassium, magnesium, and glucose?

Muscle weakness, neurological abnormalities (seizures, weakness, coma), and cardiac abnormalities.  Low magnesium can also lead to irritability or aggression.

What are the clinical signs of refeeding syndrome?

• Anorexia and weight loss
  
• Lethargy and weakness
  
• Anemia (pale mucous membranes, increased heart rate, increased respiratory rate, and bounding pulses)
  
• Nausea/vomiting              
  
• Diarrhea
  
• Restlessness
  
• Red colored urine 
  
• Seizures/coma
  
• Death

How do you treat refeeding syndrome?

• The mainstay of treatment is to start to feed starved animals slowly, and feed a diet that is high in fat and low in carbohydrates, and is balanced in potassium, phosphorus, and magnesium.
  
• Animals should be fed starting at 25% of their resting energy requirement for the first 24 hours.  RER= (weight in kilograms x 30) + 70.  Resting energy requirement is measured in kcal/day. This amount should be fed in several small meals. 
  
• Tip: the kcal/cup content of foods can be determined by going to the following great website http://www.petobesityprevention.com
  
• After the first 24 hours, the amount of food should be slowly increased over the next 3-5 days until full RER is achieved. 
  
• Phosphorus supplementation should be given to patients showing clinical signs associated with low phosphorus. Come up with a plan with your shelter veterinarian or consult a local veterinarian for dose and route of administration.  Patients that develop hemolytic anemia have an unfavorable prognosis. 
  
• Potassium chloride or potassium phosphate can be added to fluid therapy in cases of low potassium.  Come up with a plan with your shelter veterinarian or consult a local veterinarian for dose and route of administration. 
  
• IV fluid therapy is warranted in all dehydrated, starved animals, and any other supportive care that is deemed necessary.  
  
• Monitor and record patient body weight once daily. 
  
• Monitor mucous membrane color, and monitor for lethargy to evaluate for anemia. 
  
• Shelter animals suffering from starvation often have impaired immune system function, and should be placed in foster care or housed away from other shelter animals during the refeeding period. 

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References

For more information, please consult the following references and resources:

1. Starvation and Refeeding Animals Information Sheet. Accessed on www.sheltermedicine.com.
   
2. Hypophosphatemia and Refeeding Syndrome. Lippo DVM, Nathan and Byers DVM, Christopher G. Standards of Care: Emergency and Critical Care Medicine (2008) 10.4, 6-10.