The objective was to evaluate the effects of daily intake of four levels of phosphorus (8, 12, 15 and 18 g) on the metabolism of macro minerals (Ca, P, Mg, Na, K and S), including the intake, concentration in rumen, ruminal fluid passage rate, excretion in feces and apparent availability. Four rumen-fistulated buffaloes were allotted to a 4 × 4 Latin Square, with total diet composed by sugar cane as forage (85%) and concentrate formulated for each different phosphorus levels. Phosphorus levels did not caused difference in mineral concentration in the rumen of any mineral studied. Mean phosphorus concentration in the rumen content was 0.98% in the dry matter basis, whereas phosphorus content in diet ranged from 0.12 to 0.34%, demonstrating high recycling of phosphorus by saliva. Increasing phosphorus levels in the diet ranging from 8 to 18 g/anim/day did not affect the calcium and magnesium availability. Better use of phosphorus of the diet was observed at the level 15 g/day of phosphorus. The intake of increasing phosphorus levels in g/kg0.75 (X) promoted a linear increase in fecal excretion of this mineral in g/kg0.75 (Y), and low phosphorus availability values, which could be estimated using the regression equation Y = 0.03 + 0.610X, that indicate deficiency of this mineral in the diet for animal metabolism.
buffalo; minerals; rumen
