16S ribosomal RNA sequencing reveals a modulation of intestinal microbiome and immune response by dietary L-theanine supplementation in broiler chickens

Despite the availability of abundant literature on green tea, studies on the use of L-theanine (an amino acid found only in green tea) as a feed additive in poultry especially broiler are limited. So, this study was conducted to explore the effects of L-theanine on the intestinal microbiome and immune response in a broiler. A total of 400-d-old chicks were randomly divided into four treatment groups (A, B, C, and D) using a complete randomized design. Treatments were as follows: A, control (basal diet); B, basal diet + 100 mg L-theanine/kg diet; C, basal diet + 200 mg L-theanine/kg diet; and D, basal diet + 300 mg L-theanine/kg diet. Mucosal samples from ileum and jejunum of broiler chicken were extracted at 21 and 42 d of age. Extraction of genomic DNA was followed by amplification of V3 and V4 hypervariable regions of 16S ribosomal RNA. After Illumina sequencing, results revealed that treatment with L-theanine significantly increased the population of Lactobacillus in ileum and jejunum as compared to a control group, but the higher population was observed in jejunum at both 21 and 42 d of age. The overall diversity of the jejunum microbiome in the treatment group was significantly lower than that of the ileum and control group (P < 0.05). Results of this study revealed that mRNA expression of TLRs (TLR-2 and TLR-4) and cytokines (TNF-α, IFN-γ, and IL-2) was decreased in response to treatment with L-theanine. Moreover, the negative correlation of abundance of Lactobacillus was observed with expression of IL-2 and IFN-γ in the intestine and these effects were highly significant (P < 0.01). In summary, our finding revealed that dietary supplementation of L-theanine exhibited a positive influence on intestinal bacteria by supporting beneficial microbes like Lactobacillus while decreasing harmful microbes like Clostridium.

Probiotic Enhanced Intestinal Immunity in Broilers against Subclinical Necrotic Enteritis

Along with banning of antibiotics, necrotic enteritis (NE), especially subclinical NE (SNE) whereby no clinical signs are present in chicks, has become one of the most threatening problems in poultry industry. Therefore, increasing attention has been focused on research and application of effective probiotic strains, as an alternative to antibiotics, to prevent SNE in broilers. In the present study, we evaluated the effects of Lactobacillus johnsonii BS15 on the prevention of SNE in broilers. Specifically, assessment determined the growth performance and indexes related to intestinal mucosal immunity in the ileum and cecal tonsil of broilers. A total of 300 1-day-old Cobb 500 chicks were randomly distributed into the following 5 groups: control group (fed with basal diet + de Man, Rogosa, and Sharpe liquid medium [normal diet]), SNE group (normal diet), BS15 group (basal diet + 1 × 10⁶ colony-forming units BS15/g as fed [BS15 diet]), treatment group (normal diet [days 1-28] + BS15 diet [days 29-42]), and prevention group (BS15 diet [days 1-28] + normal diet [days 29-42]) throughout a 42-day experimental period. SNE infection was treated for all chicks in the SNE, BS15, treatment, and prevention groups. The present results demonstrated that BS15 supplementation of feeds in BS15 and prevention groups exerted a positive effect on preventing negative influences on growth performance; these negative influences included low body weight gain and increased feed conversion ratio caused by SNE. Although no changes were detected in all determined indexes in cecal tonsils, BS15-treated broilers were free from SNE-caused damage in villi in the ileum. BS15 inhibited SNE-caused decrease in immunoglobulins in the ileum. In the lamina propria of ileum, T cell subsets of lymphocytes influenced by SNE were also controlled by BS15. BS15 affected antioxidant abilities of the ileum and controlled SNE-induced mitochondrion-mediated apoptosis by positively changing contents and/or mRNA expression levels of apoptosis-related proteins. These findings indicate that BS15 supplementation may prevent SNE-affected growth decline mainly through enhancing intestinal immunity in broilers.