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Benzoic acid is known for its antimicrobial activity in the gut. Benzoic acid may support better nitrogen utilization, reduce diarrhea, and improve both growth performance and carcass quality. After ingestion, benzoic acid is transported to the liver, where it binds with glycine to form hippuric acid, which helps lower urinary pH and reduce ammonia emissions.
Objective: This study aimed to explore how increasing levels of benzoic acid affect nitrogen metabolism, growth, environmental impact, and carcass traits in pigs from weaning to market and to identify the optimal benzoic acid inclusion level for maximizing these benefits.
Methods: A total of 480 pigs (average weight 6.0 ± 1.5 kg) were assigned to four dietary treatments in a randomized complete block design, with initial body weight and pen group as blocking factors. The pigs were fed over six growth phases. Treatments included a control diet with antibiotics (positive control) and three levels of benzoic acid supplementation: 0.00%, 0.50%, and 1.00% in antibiotic-free diets.
Results: The diet with antibiotics led to better average daily gain and feed efficiency compared to pigs not receiving benzoic acid. However, increasing levels of benzoic acid in the diet also improved growth performance in a dose-dependent way, with optimal average daily gain observed around 0.53% benzoic acid (7.5 g/day), and best feed efficiency around 0.57% benzoic acid (8.1 g/day). Higher benzoic acid levels slightly improved nitrogen digestibility and clearly increased nitrogen retention. Supplementation with 1.00% benzoic acid lowered urine pH and reduced both ammonia emissions and the rate of ammonia release from manure over a 24-hour period. Pigs fed the antibiotic diet had greater carcass weights and backfat at the first rib than those on benzoic acid diets. Meanwhile, increasing benzoic acid levels reduced loin color and marbling but increased loin eye area, with the best results seen around 0.59% benzoic acid (8.1 g/day).
Conclusion: Dietary benzoic acid improved growth performance, nitrogen utilization, environmental outcomes, and certain carcass traits in pigs. Supplementation between 0.53% and 0.59% benzoic acid (equivalent to 7.5-8.1 g/day) provided the most consistent benefits when fed from weaning to market.
Kim SW, Choi H, Lin C, Mateo RD. Effects of increasing levels of benzoic acid fed to pigs on nitrogen utilization and metabolism affecting growth performance, ammonia emissions, and carcass characteristics. J Anim Sci. 2025; skaf101. doi: 10.1093/jas/skaf101.