Benzoic acid and essential oils modify the cecum microbiota composition in weaned piglets and improve growth performance in finishing pigs

Abstract

The objective of this study was to evaluate the effects of benzoic acid (BA) and essential oils (EO) on cellular and humoral immune response, morphology, gene expression, antioxidant capacity in the jejunal mucosa, and cecal content microbiota in weaned piglets and growth performance from the nursery to finishing phase. One hundred and twenty barrows were weaned and assigned to three treatments in a randomized block design: basal diet without additives (NC), basal diet with antibiotics (PC), and basal diet with 0.3% BA and EO (BA+EO). The pigs were weighed 0, 42, 84, and 132 days into the experiment. The incidence of diarrhea was assessed daily in the nursery phase. On days 1, 3, and 9, blood samples were collected. On day 9, these animals were euthanized to collect jejunal samples and cecal content. In the nursery phase, the PC piglets showed a greater body weight (BW) and average daily gain (ADG) and a lower feed conversion ratio (FCR) compared to the NC group, but similar levels to the BA+EO group (P < 0.050). In the growing phase, the PC treatment resulted in a greater BW and average daily feed intake (ADFI), and in the finishing phase the BW of the BA+EO group was similar to that of the PC group and greater than that of the NC group (P < 0.050). In the total period, the BW and ADG of the PC and BA+EO pigs were similar and higher than those for the NC treatment (P < 0.050). The BA+EO pigs had the lowest incidence of diarrhea during the nursery period (P < 0.050). The use of BA+EO reduced the counts of total white blood cells (WBC) and neutrophils (P < 0.050). When compared with the PC group, BA+EO supplementation significantly increased the glutathione (GSH) levels and decreased the superoxide dismutase (SOD) activity in the jejunal mucosa (P < 0.050). In the microbiome analyses, it was observed that the BA+EO and PC groups had similar cecal microbiota when compared to the NC piglets. A significant increase in the number of operational taxonomic units (OTUs) was observed in the BA+EO group. The PC and BA+EO pigs showed a lower abundance of Bacteroidetes than the NC pigs (P < 0.001). In conclusion, supplementation with BA+EO reduced the inflammatory response and modified the cecal microbiome in the post-weaning period, resulting in an improvement in the growth performance of finishing pigs.