PSII-12 Dose-dependent effects of supplemental benzoic acid on nitrogen balance, urinary pH, slurry pH, and manure odorous compounds in pigs

Abstract

Abstract The objective of this study was to determine the effects of supplemental benzoic acid (BA) at 0.5% to 2.5% in diets on nitrogen (N) utilization, urinary pH, slurry pH, and manure odorous compounds in pigs. Fifteen barrows with an initial body weight of 56.2 kg (standard deviation = 2.6) were individually housed in metabolism crates. The animals were allocated to a replicated 6 × 4 incomplete Latin square design with 12 animals, 6 experimental diets, and 4 periods, resulting in 8 observations per dietary treatment. The basal diet mainly consisted of corn, soybean meal, and rapeseed meal. Benzoic acid was supplemented to the basal diet at 0.0%, 0.5%, 1.0%, 1.5%, 2.0%, or 2.5% BA at the expense of corn starch. Each period consisted of a 4-d adaptation period and a 24-h collection period for slurry followed by a 4-d collection period for feces and urine. On d 5, feces and urine were collected for 24 h, and the feces and urine were mixed in a ratio of fecal weight to urine weight at the end of the collection to obtain slurry samples. The apparent total tract digestibility of N tended to linearly increase (P = 0.071) and the daily digested N linearly increased (P < 0.05) with increasing BA supplementation. In contrast, the urinary N output and retained N were not affected by inclusion of BA. The urinary and slurry pH were quadratically decreased (P < 0.05) with increasing BA supplementation. In the fecal samples, the concentrations of acetate, propionate, butyrate, and skatole linearly decreased (P < 0.05) and isovalerate concentration tended to linearly decrease (P = 0.099) by supplemental BA. In the slurry samples, the concentrations of isovalerate and skatole decrease linearly (P < 0.05), and butyrate concentration tended to linearly decrease (P = 0.054) by supplemental BA. In conclusion, supplemental benzoic acid has the potential to improve the N digestibility in a dose-dependent manner for pigs. In addition, increasing benzoic acid supplementation decreased urinary pH, slurry pH, and concentrations of some odorous compounds in pig feces and slurry.