The objective of this work was to determine the maintenance requirement and the deposition efficiency of lysine in growing pigs. It was used the incomplete changeover experimental design, with replicates over time. Twelve castrated pigs with average body weight (BW) of 52±2 kg were kept in metabolism crates with a controlled temperature of 22ºC. The diets were formulated to supply 30, 50, 60, and 70% of the expected requirements of standardized lysine, and provided at 2.6 times the energy requirements for maintenance. The trial lasted 24 days and was divided into two periods of 12 days: seven days for animal adaptation to the diet and five days for sample collection. The increasing content of lysine in the diet did not affect dry matter intake of the pigs. The amount of nitrogen excreted was 47% of the nitrogen intake, of which 35% was excreted through feces and 65% through urine. The estimated endogenous losses of lysine were 36.4 mg kg-1 BW0.75. The maintenance requirement of lysine for pigs weighing around 50 kg is 40.4 mg kg-1 BW0.75, and the deposition efficiency of lysine is 90%.
amino acid requirement; nitrogen; pig production; swine nutrition