Effects of different acidifiers on the growth performance and diarrhea score of weaned piglets under commercial pig farm conditions.

Benzoic acid (BA)-based acidifiers are widely applied in nursery diets; however, formulation can shape their functional outcomes on intake, host robustness, and gut microbial ecology. This study assessed a new-type benzoic acid (NBA) strategy under commercial farm conditions. A total of 210 21-day-old DLY (Duroc × Landrace × Yorkshire) weaned piglets, with equal numbers of males and females and similar body weight (average 6.03 kg ± 0.01 kg), were randomly assigned to 5 groups with 6 replicates per group and 7 piglets per replicate. The control group was fed a basal diet, while the four experimental groups were fed the basal diet supplemented with 0.5% benzoic acid (BA), 0.3% new-type benzoic acid (NBA), 0.25% controlled-release-coated benzoic acid (CBA), or 0.5% compound acidifier (CA) powder, respectively. The trial lasted 42 days. The results showed that compared to the control group, the average daily feed intake (ADFI) from days 15 to 28 was significantly increased (P < 0.05) in the BA, NBA, and CA groups, indicating improved voluntary intake during the mid-nursery period. The diarrhea rate was significantly reduced (P < 0.05) during days 0-14 in the BA, NBA and CBA groups compared to the control group. Compared to the control group, serum total antioxidant capacity (T-AOC) was significantly elevated (P < 0.05) in the BA, CBA, and CA groups, and catalase (CAT) levels increased significantly in the NBA group. White blood cell (WBC), lymphocyte (Lym), and mean corpuscular hemoglobin concentration (MCHC) increased significantly in the BA group compared to the control group, while MCHC levels decreased significantly in the NBA, CBA, and CA groups. Notably, compared with the control group, 0.5% BA, 0.3% NBA, and 0.25% CBA increased the richness and diversity of the intestinal microbiota. Specifically, these treatments promoted the growth of beneficial bacteria such as Lactobacillus while inhibiting the proliferation of Escherichia coli. The results of this study indicate that adding 0.5% BA, 0.3% NBA, and 0.25% CBA all enhance piglets' antioxidant capacity, reduce diarrhea incidence, and enhance gut microbial diversity. Among these, 0.5% BA and 0.25% CBA demonstrated superior efficacy compared to 0.3% NBA, offering potential economic benefits by improving feed efficiency, thereby enhancing overall production performance.