Silymarin improved the growth performance via modulating the microbiota and mucosal immunity in Escherichia coli-challenged broiler chicks

Abstract

The present study was carried out to investigate the effects of dietary supplemental silymarin on growth performance, intestinal microbiota, and jejunal health indices in broiler chicks challenged with Escherichia coli (E. coli) O78:K80. For this purpose, 384 seven-day-old Ross broiler chicks were randomly allocated to eight experimental treatments with four replicates of 12 birds each. The treatments consisted of two microbial conditions (unchallenged and challenged with E. coli O78:K80) with further division into four additive supplementations (no additive, additions of 500 and 1000 ppm of silymarin, and antibiotic addition as the positive control). The birds were orally infected with E. coli O78:K80 at 1 × 109 cfu from 7 to 28 d of age. Results showed that E. coli infection led to the declines (P < 0.001) in average daily feed intakes (ADFI) and average daily weight gains (ADWG), however feed conversion ratios (FCR; P < 0.001) were increased in the grower, finisher, and whole trial periods. The relative weights of carcass, heart, gall bladder, and pancreas were unaffected in the E. coli-infected broilers. E. coli challenge markedly (P < 0.001) increased the ileal E. coli, Salmonella spp, Klebsiella spp, and total Gram-negative bacteria counts at 28 and 42 d of age. Challenging with E. coli led to marked (P < 0.001) decreases in villi height, villi height to crypt depth (VH:CD) ratio and villi absorptive area, where as it resulted in noticeable (P < 0.001) rises in jejunal goblet cell counts (GCC), and lamina propria lymphoid follicle numbers (LLFN) and diameter (LLFD) at 28 and 42 d of age. Dietary inclusion of silymarin not only led to rises (P < 0.001) in ADFI and ADWG, but also it improved FCR throughout the experimental period. Supplemental silymarin caused highly significant (P < 0.001) declines in the mentioned ileal microflora at 28 and 42 d of age. The increases in both jejunal villi height (P < 0.01) and VH:CD ratio (P < 0.001), as well as a reduction in crypt depth (P < 0.05) were observed after dietary silymarin supplement. Furthermore, it was also found that silymarin modulated the GCC (P < 0.001) and LLFN (P < 0.01). The results indicate that silymarin administration could improve the growth performance via suppressing the ileal pathogen microbial numbers and enhancing the villi absorptive surface area in the E. coli-infected broiler chicks.