PSII-13 - Effects of benzoic acid, bromelain, adipic acid, and humic substance supplementation on nitrogen balance, urine pH, slurry pH, and manure odorous compounds in pigs

Abstract: The objective of the present study was to evaluate the effects of benzoic acid, bromelain, adipic acid, and humic substance supplementation on nitrogen balance, urinary pH, slurry pH, and manure odorous compounds in pigs. Fifteen barrows with an initial body weight of 37.9 kg (standard deviation = 4.1) were individually housed in metabolism crates. The animals were allocated to a triplicated 5 × 2 incomplete Latin square design with 15 animals, 5 experimental diets, and 2 periods. The basal diet was mainly consisted of corn, soybean meal, and rapeseed meal. Four experimental diets were prepared by supplementing each additive at a concentration of 10 g/kg at the expense of corn starch to the basal diet. Each period consisted of a 4-day adaptation period and a 24-h collection period for slurry, followed by a 4-day collection period for feces and urine. On day 5, feces and urine were collected for 24 hours, 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 fecal nitrogen (N) output was the greatest (P < 0.05) in the pigs fed the diet supplemented with humic substances. The apparent total tract digestibility of N in pigs fed the humic substance diet was the least (P < 0.05) than other groups. The urinary pH in pigs fed the adipic acid diet was less (P < 0.05) than that in other groups except the benzoic acid group. The slurry pH tended to differ among the treatment groups (P = 0.074) with the least value in the pigs fed the adipic acid diet. The concentrations of indole in slurry (P = 0.084) and isovalerate in feces (P = 0.062) tended to differ among the groups with the least values in the pigs fed the humic substance diet. In conclusion, benzoic acid supplemented has potential to increase N utilization in pigs, and adipic acid supplemented to pig diets can decrease urinary pH and slurry pH. Although benzoic acid and adipic acid have the limited effects in reducing odorous compounds, humic substances have potential to reduce some odorous compounds.