Metabolic responses of chronically starved horses to refeeding with three isoenergetic diets.

OBJECTIVE To examine metabolic responses of chronically starved horses to refeeding with 3 isoenergetic diets. DESIGN Uncontrolled clinical trial. ANIMALS 22 mature mixed-breed horses that were emaciated but otherwise clinically normal. PROCEDURE Horses were fed 1 of 3 diets: alfalfa hay, oat hay, or a combination diet of half oat hay and half commercially prepared ration. Digestible energy of diets was gradually increased throughout the refeeding period. One pre- and 4 postprandial blood samples were obtained daily, and analyses included RBC count, Hct, and determination of hemoglobin, glucose, insulin, free fatty acid, total bilirubin, 2,3-diphosphoglyceric acid, phosphorus, magnesium, calcium, sodium, and potassium concentrations. Body weight, fecal output, and feed and water consumption were measured and recorded daily. Repeated-measures ANOVA was used to examine dietary and temporal (day) effects of the 3 dietary regimens during 10-day trials. RESULTS 19 Horses survived. Three horses (2 fed alfalfa diet, 1 fed combination diet) died of metabolic or gastrointestinal problems. Increasing temporal effects in serum concentrations of glucose, insulin, magnesium, calcium, and sodium; decreasing temporal effects in serum concentrations of free fatty acid, 2,3-diphosphoglyceric acid, and phosphorus; and dietary effects in serum concentrations of glucose, insulin, magnesium, and potassium were detected in the 19 surviving horses. Serum phosphorus and free fatty acid concentrations decreased dramatically during the first 5 days of refeeding with all 3 diets. Serum magnesium concentrations increased in horses fed the alfalfa hay diet, whereas improvement was not evident in horses fed oat hay or combination diets. Horses receiving the alfalfa and oat hay diets had lower postprandial glucose and insulin concentrations than horses receiving the combination diet. Horses fed oat hay alone ate 92% of feed offered, compared with 98% feed consumption for horses fed alfalfa hay or combination diets. CLINICAL IMPLICATIONS Clinically normal emaciated horses can be successfully rehabilitated by gradual refeeding with a high forage diet.