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 […]