A static, empirical and determinist model of ingestion, retention and excretion of N and P was developed for the Brazilian pig production. The general principles were: technological systems (ST), animal categories, N and P in the diets, and digestive and metabolic efficiencies of N and P. The model integrates three aggregation levels, being constituted by ten compartments (ingestion, gastrointestinal contents, retention, and excretions of P and N), 300 sub-compartments (50 related to ST and 250 to animal categories). The ST was defined by the number of slaughter animals/sow/year. The flows of N and P among compartments and temporary relations were the same as literature data. The simulated N ingestion and retention were of 193 and 46 thousand t, respectively. The simulated N excretion by fecal and urinary was 37 and 110 thousand t, respectively. Approximately 58% of N ingestion, 77% of N retention and 52% of N excretion were observed in the high ST. The simulated P ingestion and retention were of 46 and 11 thousand t, respectively. The simulated P fecal and urinary excretion was of 29 and 6 thousand t, respectively. This model is adequate to simulate N and P flows for systems of high and medium technologies of the Brazilian pig production.
model; nutrition; feeding; pigs
