Nitrogen balance response to varying levels of dietary protein in slow-growing Windsnyer pigs

Abstract

Protein requirements for slow-growing pigs have not been defined. The study was designed to determine the relationship between the level of dietary protein and nitrogen balance in slow-growing Windsnyer pigs. Thirty Windsnyer pigs with an initial bodyweight of 34.7 (SD = 0.85) kg were randomly assigned to six experimental diets containing 193, 174, 154, 135, 117, and 97 g/kg of crude protein (CP). Pigs were penned individually. There were five pigs in each diet. The faecal nitrogen output (NFO) showed a decreasing quadratic relationship with protein level. A linear relationship between protein level and urinary nitrogen excretion was observed (P =0.0001). The total nitrogen excreted showed a significant quadratic relationship to decreasing levels of CP in the diets (P =0.0001). The apparent digestibility of nitrogen had a linear relationship with dietary CP level (P =0.0005). A quadratic relationship between dietary protein level and N utilization was observed (P =0.0001). The optimum protein level for total nitrogen excreted, nitrogen utilization and biological value of feed protein were attained at 135 g/kg protein level. The efficiency of nitrogen utilization supports the low protein diet. The present results suggest reducing the dietary protein level for Windsnyer pigs to decrease amount of excreted N that is deposited into the environment.