The objective of this work was to evaluate the effects of different P levels in the alimentary diet of growing horses on the endogenous fecal losses, and to verify the real daily minimum requirement of this element for their feeding. Sixteen male horses receiving a basal diet with no phosphorus supplementation and basal diet supplemented with dicalcium phosphate to provide P intake of 15, 20 and 25 g/animal/day were used. At the 16th day of the trial, each horse was intravenously injected with 30 MBq of 32P/animal, and blood, feces and urine were collected for seven days at 24 hours intervals. The specific activities of the radiophosphorus in the plasma, feces and urine were determined and the fecal endogenous loss and true phosphorus absorption were calculated. Fecal endogenous loss and true phosphorus absorption were unaffected (P>0.05) by P levels, and the average of 10.34 mg P/kg/BW/day and 47.07%, respectively, was estimated. Therefore, the horses in this experiment required 21.96 mg P/kg/BW/day to balance fecal endogenous loss, and phosphorus daily requirement of 14.75 g.
horses; diet; nutritional requirements; mineral nutrients; nutritional losses; defecation; animal nutrition
