The objective of this experiment was determine the appropriate level of phytase (0, 300, 600 and 900PU/kg of the diet) to be added in swine diets containing two levels of crude protein (CP), one in the demand of the animal (18% - NRC, 1988) and another in lower level (16%), for evaluation of the most effective reduction in excretion of nitrogen, phosphorus and calcium, to avoid larger environmental problems. Twenty four pigs with an initial avearage weight of 18.4kg were housed in metabolic cages for determination of the nitrogen, phosphorus and calcium metabolism through the method of total colection of faeces using ferric oxide as a marker. The diets were supplied for the animals related to their metabolic weight, and were isoenergetic with 3295kcal of ME/kg. The parameters evaluated were the amount of consumed and total excreted nitrogen; amount of phosphorus and calcium consumed and excreted in the feces and in the urine. An increase in the biodisponibility of these nutrients was observed when the phytase was added in the levels between 421 - 466PU/kg of the diet.
calcium; enzyme; excretion; nitrogen; phosphorus; phytate
