Fat Supplementation to Alfalfa Diets for Refeeding the Starved Horse

The objective was to examine the metabolic responses of chronically starved horses using two isoenergetic diets consisting of either 100% alfalfa hay (AH) or 80% alfalfa hay with 20% corn oil (AO), on a caloric basis. Two 10-d trials were conducted using 14 emaciated, but otherwise healthy, horses with an initial mean body condition score of 1.8 ± 0.9 and mean BW of 336 ± 31 kg. The initial DE intake of 50% of maintenance was gradually increased to 100% during the 10-d refeeding period. Two of the horses receiving the AH diet were euthanized, thus 12 horses (AH, n = 7; AO, n = 5) survived the 10-d study. One preprandial and four postprandial venous blood samples were collected daily. Dietary effects (P<0.01) were shown for blood serum or plasma free fatty acids (FFA), phosphate, magnesium, and 2,3-diphosphoglycerate (2,3-DPG), but not glucose, insulin, or potassium concentrations. The response of insulin and FFA during the 10-d study showed differences (P<0.05) between AH and AO diets. Serum phosphate concentration in horses on both diets exhibited a general slow decline with concentrations below normal reference range during d 5 through 10, thus indicating hypophosphatemia. Serum magnesium increased in horses consuming the AH diet, whereas concentrations in horses consuming the AO diet consistently were below reference range, leading to mild hypomagnesemia. Hypokalemia did not develop in either treatment group, as all serum potassium concentrations remained in the normal reference range. The substitution of corn oil in isoenergetic alfalfa diets was not advantageous in minimizing or preventing hypophosphatemia or hypomagnesemia for refeeding starved horses. The AH diet is recommended as more supportive in refeeding starved horses because of the greater intake of dietary phosphorous and magnesium.