Escherichia coli O88 induces intestinal damage and inflammatory response through the oxidative phosphorylation and ribosome pathway in Pekin ducks.

Colibacillosis is one of the major health threats in the poultry industry worldwide. Understanding the pathogenic mechanisms involved in Escherichia coli-induced inflammatory response may lead to the development of new therapies to combat the disease. To address this, a total of 96 1-day-old male lean Pekin ducklings were employed and randomly allocated to two treatments, each with six replicates of eight ducks. Ducks in the experiment group (EG) and the control group (CG) were separately orally administered with 0.2 ml of pathogenic E. coli O88 (3 × 109 CFU/ml) or equivalent volumes of 0.9% sterile saline solution on day 7, two times with an 8-h interval. Serum and intestinal samples were collected on days 9, 14, and 28. Results showed that ducks challenged with E. coli had lower average daily gain and higher feed intake/weight gain during days 9-14 and overall (P < 0.05). Histopathological examination showed that E. coli decreased the villus height and the ratio of villus height/crypt depth in the jejunum (P < 0.05) on days 9 and 14. The intestinal barrier was disrupted, presenting in E. coli ducks having higher serum DAO and D-LA on days 9 and 14 (P < 0.05) and greater content of serum LPS on day 9 (P < 0.05). Escherichia coli infection also triggered a systemic inflammatory response including the decrease of the serum IgA, IgM, and jejunal sIgA on day 14 (P < 0.05). In addition to these, 1,062 differentially expressed genes were detected in the jejunum tissues of ducks by RNA-seq, consisting of 491 upregulated and 571 downregulated genes. Based on the KEGG database, oxidative phosphorylation and the ribosome pathway were the most enriched. These findings reveal the candidate pathways and genes that may be involved in E. coli infection, allow a better understanding of the molecular mechanisms of inflammation progression and may facilitate the genetic improvement of ducks, and provide further insights to tackle the drug sensitivity and animal welfare issues.

Effects of glucose oxidase on growth performance, immune function, and intestinal barrier of ducks infected with Escherichia coli O88.

The negative effects of dietary antibiotics have become a widespread concern. It is imperative to search for a new type of green, safe, and efficient feed additive that can replace antibiotics. This study was to investigate the effects of glucose oxidase (GOD) on growth performance, immune function, and intestinal barrier in ducks infected with Escherichia coli O88. First, we established the E. coli challenge model of ducks through a preliminary experiment and then carried out the formal experiment by using 144 1-day-old male lean Peking ducklings (50 ± 2.75 g). All ducks were randomly assigned to 1 of 3 dietary treatment groups of basal diet (control), 30 mg/kg virginiamycin (antibiotic), and 200 U/kg GOD (1,000 U/g). Each group consisted of 6 replications with 8 birds per replicate. At day 7, all ducks were orally administered 0.2 mL E coli O88 (3 × 109 cfu/mL) twice, 8 h apart based on the preliminary experiment. The experiment lasted for 28 d. Dietary supplementation with GOD improved growth performance of ducks infected with E. coli. The GOD increased contents of Ig in plasma and secreted Ig A in jejunal mucosa. The GOD group had lower concentrations of inflammatory cytokines (tumor necrosis factor-α, IL-1ß, and IL-6) and their upstream regulator Toll-like receptor 4 in the jejunum of ducks than the control group. Supplementation with GOD increased villus height and decreased crypt depth in the jejunum. The gene expression of tight junction proteins (zonula occludens-1, claudin-1 and claudin-2) was enhanced by adding GOD. The GOD decreased intestinal permeability by reducing the concentrations of diamine oxidase and D-lactic in plasma of ducks. There were no significant differences in almost all the indices tested between the GOD and the antibiotic groups. In conclusion, supplementation of GOD improved growth performance, immune function, and intestinal barrier of ducks infected with E. coli O88. Glucose oxidase may serve as a promising alternative therapy to antibiotics to relieve or prevent colibacillosis in ducks.

Effects of Fermentation on Standardized Ileal Digestibility of Amino Acids and Apparent Metabolizable Energy in Rapeseed Meal Fed to Broiler Chickens.

Rapeseed meal (RSM) is a common protein ingredient in animal diets, while the proportion of RSM in diets is limited because of its anti-nutritional factors. Fermentation based on mixed microbial strains appears to be a suitable approach to improve the nutritive value of rapeseed meal in animal feed. In this study, we evaluated the effects of fermentation on the apparent metabolizable energy (AME) values and standardized ileal digestibility (SID) of amino acids in RSM fed broilers. The AME and nitrogen-corrected apparent metabolizable energy (AMEn) values of RSM and fermented rapeseed meal (FRSM) were determined by the substitution method, with RSM and FRSM proportionally replacing the energy-yielding components of the basal diet by 30%. Results show that fermentation improved AME and AMEn of RSM from 7.44 to 8.51 MJ/kg and from 7.17 to 8.26 MJ/kg, respectively. In the second experiment, two experimental diets were formulated, with RSM and FRSM being the sole sources of amino acids. A nitrogen-free diet (NFD) was also formulated to determine endogenous amino acids losses (EAAL). Feeding on FRSM resulted in higher (p < 0.05) apparent ileal digestibility (AID) and SID of alanine, valine, isoleucine, leucine, tyrosine, lysine, arginine, and phenylalanine. No significant differences between RSM and FRSM were found for AID and SID of asparagine, histidine, threonine, serine, glutamine, praline, glycine, methionine, and cystine. FRSM had greater AMEn values and SID of amino acids compared to RSM, therefore, FRSM was nutritionally superior to RSM in broiler diets.

Regulation of the expression of key signalling molecules in mTOR pathway of skeletal muscle satellite cells in neonatal chicks: Effects of leucine and glycine-leucine peptide.

This study was conducted to analyse the effects of leucine (Leu) and glycine (Gly)-Leu peptide on expressions of key signalling molecules in mTOR pathway of skeletal muscle satellite cells in neonatal chicks. The 4-day-old male AA broilers with similar weight were selected to obtain the broiler skeletal muscle satellite cells with the two-step method of collagenase-I and trypsin digestion. The satellite cells were subjected to primary culture in vitro, and they were cultured in DMEM medium with the Leu concentration of 0.2 mM and 2 mM as well as with the Gly-Leu peptide concentration of 0.2 mM and 2 mM. The experiment lasted for 5 days. The results showed that TOR, S6K1 and 4E-BP1 mRNA expressions in the medium with Leu concentration of 2 mM were significantly higher than that in 0.2 mM group (p < 0.05). There was no difference between the medium with Gly-Leu concentration of 2 mM and 0.2 mM on the TOR, S6K1 and 4E-BP1 mRNA expressions (p > 0.05). In conclusion, Leu significantly increases TOR, S6K1 and 4E-BP1 mRNA expressions of skeletal muscle satellite cells, but Gly-Leu peptide has no effect on them.