A static, empirical and determinist model of ingestion, retention and excretion of Nitrogen (N) and Phosphorus (P) was developed for the pig production at Rio Grande do Sul state, Brazil. The general principles were: technological systems (ST), animal categories, N and P in diets, and digestive and metabolic efficiencies of N and P. The model integrates three aggregation levels, being constituted by ten compartments (ingestion, gut fill, retention, and excretions of P and N), 300 sub-compartments (50 related to ST and 250 to animal categories). The ST was defined by number of slaughter animals per sow per year. The flows of N and P between compartments and temporary relationships followed literature data. Simulated N ingestion and retention was 34 and 8 thousand tons, respectively. Simulated N excretion by fecal and urinary ways was 6 and 18 thousand tons, respectively. Approximately 90% of N ingestion, 98% of N retention and 85% of N excretion were observed in the medium and high ST. Simulated ingestion and retention of P was 8 and 2 thousand tons, respectively. Simulate P excretion by fecal and urinary ways was 5 and 1 thousand tons, respectively. This model is able to simulate N and P flows in high and medium technological systems of pig production at Rio Grande do Sul state, Brazil.
environment; excretion; model; nutrition; swine
