Phytogenic feed additives alleviate pathogenic Escherichia coli-induced intestinal damage through improving barrier integrity and inhibiting inflammation in weaned pigs

This study was conducted to investigate the effect of each phytogenic feed additive (PFA) on the growth performance, nutrient digestibility, intestinal morphology, and immune response of weaned pigs challenged with Escherichia coli. A total of 63 4-week-old weaned pigs with initial body weight of 8.03 ± 0.43 kg were placed in individual metabolic cages, and then randomly assigned to 7 treatment groups. The 7 treatments were as follows: (1) NC: basal diet without E. coli challenge, (2) PC: basal diet with E. coli challenge,( 3) T1: PC + 0.04% bitter citrus extract, (4) T2: PC + 0.01% microencapsulated blend of thymol and carvacrol, (5) T3: PC + 0.10% mixture of bitter citrus extract and microencapsulated blend of thymol and carvacrol, (6) T4: PC + 0.04% premixture of grape seed and grape marc extract, green tea and hops, (7) T5: PC + 0.10% fenugreek seed powder. The experiments progressed in 21 d, including 7 d before and 14 d after the first E. coli challenge (d 0). In the E. coli challenge treatments, all pigs were orally inoculated by dividing a total of 10 mL of E. coli F 18 for 3 consecutive days from d 0 postinoculation (PI). Compared with PC treatment, the PFA-added treatment groups significantly increased (P < 0.05) average daily gain and feed efficiency, and decreased (P < 0.05) the fecal score at d 0 to 14 PI. Tumor necrosis factor α was significantly lower (P < 0.05) in the PFA-added treatment groups except for T1 in d 14 PI compared with the PC treatment. T3 showed significantly higher (P< 0.05) villus height:crypt depth and claudin 1 expression in ileal mucosa, and significantly downregulated (P < 0.05) the expression of calprotectin. In conclusion, the addition of PFA in weaned pigs challenged with E. coli alleviated the negative effects of E. coli and improved growth performance. Among them, the mixed additive of bitter citrus extract and essential oils showed the most effective results, improving immune response, intestinal morphology, and expression of tight junctions.

Key Words: barrier integrity, immunity, phytogenic feed additive, postweaning diarrhea, weaned pig.

Published in the proceedings of the 10th Symposium on Gut Health in Production of Food Animals 2022, St. Louis, USA.