Comparative efficacy of antibiotic growth promoter and benzoic acid on growth performance, nutrient utilization, and indices of gut health in nursery pigs fed corn-soybean meal diet

Benzoic acid (BA) supplement was evaluated as an alternative to antimicrobial growth promoter (AGP). Ninety-six piglets (21-d-old at weaning) were placed in pens (four piglets pen(-1)) based on body weight (BW) and allocated (n = 8) to either control corn-soybean meal diet or control + in-feed antibiotic (AGP, 220 mg chlortetracycline hydrochloride and 31.2 mg tiamulin kg(-1)) or control + 0.5% BA. Feed intake and BW were measured weekly. Fecal scores for incidence of diarrhea and fecal samples for apparent total tract digestibility (ATTD) of components were taken in week 2. One pig per pen was euthanized on day 14 for jejunal histomorphology and digesta for pH and short-chain fatty acids concentration. In weeks 1-6, pigs fed AGP and BA had better (P < 0.01) gain to feed ratio compared with control fed pigs. On day 12, pigs fed AGP and BA showed lower (P = 0.01) fecal score than control fed pigs. Pigs fed BA had (P < 0.05) higher ATTD of crude protein and taller villi compared with the control or AGP fed pigs. Pigs fed AGP showed higher (P = 0.05) lactic acid concentrations than pigs fed BA, however, none differed (P > 0.05) with control pigs. In conclusion, BA supported piglet growth performance to the same extent as AGP.