PSXI-16 Nitrogen Excretion and Urine Ph in Growing Pigs Decreased By Reducing Dietary Protein Concentrations

Abstract

Abstract The objective of the present work was to determine effects of reducing dietary crude protein (CP) concentrations with indispensable amino acid (AA) supplementation on nitrogen balance and urinary pH in growing pigs. Three experiments were conducted using 12 barrows with an initial body weight of 29.9, 50.2, and 78.2 kg (standard deviation = 1.8, 2.2, and 3.7, respectively) individually housed in metabolism crates. In each experiment, a quadruplicated 3 × 2 incomplete Latin square design with 3 diets varying CP concentrations in each experiment and 2 periods per square was employed. In experiments 1 and 2, experimental diets based on corn, soybean meal, corn distillers dried grain with solubles, and rapeseed meal were formulated to contain 16.8, 15.0, and 13.2% CP as-fed basis and 16.8, 14.9, and 13.1% CP as-fed basis, respectively. In experiment 3, experimental diets based on corn and soybean meal were formulated to contain 15.1, 13.2, and 11.4% CP as-fed basis. All diets were supplemented with indispensable AA to meet all indispensable AA requirements. Each period consisted of a 5-day adaptation period followed by a 4-day collection period. On days 6 and 10, chromic oxide was added at 0.5% in morning meals as a marker and the marker-to-marker procedure was used for the quantitative collection of feces. Urine collection was initiated at 10:00 on day 6 and terminated at 10:00 on day 10. Polynomial contrasts were performed to test linear and quadratic effects of dietary CP concentrations on the response variables in each experiment. In all experiments, daily N intake was linearly decreased (P < 0.05) with decreasing dietary CP concentrations. Decreasing dietary CP concentrations resulted in linear reduction in daily fecal N excretion (P < 0.05) in experiment 2 and linear reductions in daily urinary N excretion (P < 0.05) in all experiments. Total N excretion linearly decreased (P < 0.05) with decreasing dietary CP concentration in all experiments. The urinary pH obtained from 30- and 50-kg pigs was linearly decreased (P < 0.05) with decreasing dietary CP concentrations. In conclusion, lowering dietary CP concentrations decreased N excretion and urinary pH in 30-, 50-, and 78-kg pigs.