This study aimed at determining the biological phosphorus (P) availability of different P sources for growing horses. Sixteen young male horses submitted to the application of four phosphate sources -- rocks phosphate Tapira (RPT) and Patos de Minas (PAT), dicalcium phosphate (DIC) and bone meal (BOM) -- added to the basal diet in quantities sufficient to supply 22 g of P/animal/day were used. At the 16th day, the animals were injected with 30 MBq/animal, and blood, feces and urine were collected for seven days. The specific activities of plasma, feces and urine were determined and fecal endogenous loss and true phosphorus absorption were calculated. Values of intake, excreted, plasma and retained phosphorus were unaffected by phosphates sources (P>0.05). The true absorption values were 25.23%, 33.97%, 31.71% and 29.36% for RPT, PAT, DIC and BOM, respectively. There was no difference (P>0.05) among sources. Rock phosphate availabilities were high in relation to dicalcium phosphate.
horses; diet; nutritional requirements; mineral nutrients; nutritional losses; defecation; animal nutrition
