209 Lowering Dietary Crude Protein Concentration Decreases Nitrogen Excretion and pH of Urine and Slurry in 15-kg Nursery Pigs

Abstract

Abstract The objective of the present work was to determine the effects of reucing dietary crude protein (CP) concentrations with essential amino acid (EAA) supplementation on nitrogen balance, urinary pH, and slurry pH in nursery pigs. Twelve barrows with an initial body weight of 15.2 kg (standard deviation = 0.7) were individually housed in metabolism crates. A quadruplicated 3 × 2 incomplete Latin square design with 3 experimental diets and 2 periods per square was employed. Experimental diets based on corn, soybean meal, whey powder, fish meal, and blood plasma were formulated to contain 19.4% CP, 17.5% CP, and 15.7% CP by reducing inclusion rates of soybean meal. All experimental diets were supplemented with EAA to meet all EAA requirements. Each period consisted of a 4-day adaptation period and a 24-hour collection period followed by a 4-day collection period. On day 5, feces and urine were collected for 24 h and the feces and urine were mixed in a ratio of fecal weight and urine weight at the end of collection to obtain slurry samples. Then, pH of urine and slurry samples was measured immediately. 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 1000 h on day 6 and terminated at 1000 h on day 10. Orthogonal polynomial contrasts were performed to test linear and quadratic effects of dietary CP concentrations on the response variables. Daily N intake was linearly decreased with decreasing dietary CP concentrations (P < 0.05). Daily fecal and urinary N excretions linearly decreased with decreasing dietary CP concentrations (P < 0.05), whereas N retention rate as % of intake was linearly increased with decreasing dietary CP concentrations (P < 0.05). The urine pH and slurry pH were linearly decreased with decreasing dietary CP concentrations (P < 0.05). In conclusion, lowering dietary CP concentrations decreased N excretion and pH of urine and slurry.