Effects of increasing levels of benzoic acid fed to pigs on nitrogen utilization and metabolism affecting growth performance, ammonia emissions, and carcass characteristics

The objectives of this study were to investigate the effects of increasing levels of benzoic acid (BA) on nitrogen utilization and metabolism affecting growth performance, ammonia emissions, and carcass characteristics, and to determine the optimal levels of BA for the growth performance and carcass characteristics when fed to pigs from weaning to market. A total of 480 pigs (6.0 ± 1.5 kg) were assigned to 4 dietary treatments in a randomized complete block design with initial body weight and group as blocks and were fed in 6 phases. Treatments included a basal diet with antibiotics (positive control, PC) and diets with 3 levels of BA (0.00%, 0.50%, and 1.00% BA) without antibiotics. The PC increased (P < 0.05) the average daily gain (ADG) and G:F during the overall period compared to no BA supplementation. Increasing levels of BA increased (P < 0.05) overall ADG quadratically (maximum at 0.53% or 7.5 g/d of BA). Increasing levels of BA increased (P < 0.05) overall G:F quadratically (maximum at 0.57% or 8.1 g/d of BA). Increasing levels of BA tended to increase (linear, P = 0.096) N digestibility and increased (linear, P < 0.05) N retention. The BA supplementation at 1.00% decreased (P < 0.05) urine pH and aerial ammonia emission from manure compared to no BA supplementation in the 24 h collection period. The BA supplementation at 1.00% decreased (P < 0.05) rate of change in aerial ammonia emission compared to no BA supplementation in the 24 h collection period. The PC increased (P < 0.05) shrink weight, hot carcass weight, and first rib backfat compared to no BA supplementation. Increasing levels of BA decreased (P < 0.05) loin color and marbling score linearly and increased (P < 0.05) the loin eye area quadratically (maximum at 0.59% or 8.1 g/d of BA). In conclusion, supplementation of BA in feeds enhanced growth performance, improved N utilization, reduced urine pH, reduced aerial ammonia emissions, and improved carcass characteristics of pigs. Supplementation of BA at a range of 0.53% to 0.59% (corresponding to 7.5 to 8.1 g/d of BA based on overall average daily feed intake) provided the optimal improvements in body weight gain, feed efficiency, and carcass characteristics when fed to pigs from weaning to market.