Abstract
Increased intestinal permeability (IP) and inflammation are both linked with functionality of the intestinal barrier and in particular enterocytes. Currently, almost all assessment methods of the intestinal barrier function are invasive. The present study aimed to quantify selected proteins as novel biomarkers in excreta of broiler chickens to facilitate non-invasive assessment of gut barrier function using enzyme-linked immunosorbent assays (ELISA). It was further hypothesised that probiotics as feed additives may counteract gut barrier dysfunction. A 3 × 2 factorial arrangement of treatments was used with the main factors being gut barrier dysfunction models (control, rye-based diet, and dexamethasone–DEX) with and without probiotic supplementation (a three-strain Bacillus) using 72 male Ross 308 day-old chickens. Each of the 6 experimental treatments was replicated 12 times. On d 21 of age, fluorescein isothiocyanate dextran (FITC-d) uptake into serum was examined to test IP. Fresh excreta samples were collected on d 20. The biomarkers included alpha-1 antitrypsin (A1AT), intestinal fatty acid binding protein (I-FABP), lipocalin-2 (LCN2), fibronectin (FN), intestinal alkaline phosphatase (IAP), ovotransferrin (OVT) and superoxide dismutase [Cu-Zn] (SOD1). Only DEX increased (P<0.001) FITC-d passage to the blood on d 21 of age, indicating a greater IP. The excreta concentrations of A1AT, I-FABP and SOD1 were unaltered by the experimental treatments. DEX increased (P<0.05) FN concentration in excreta compared with control birds. Conversely, inclusion of rye in the diet reduced (P<0.05) FN but increased (P<0.001) OVT in excreta. Independently, DEX decreased IAP (P<0.05) in excreta compared with control and rye-fed birds. The excreta concentration of LCN2 tended (P = 0.086) to increase in birds injected by DEX. There was no demonstrable effect of probiotic addition on any of the studied parameters. Among the tested biomarkers, FN, IAP, and LCN2 revealed promise as biomarkers of intestinal barrier function quantified by ELISA kits.
Highlights
Maintaining and improving gut health is fundamentally important as the gut supports optimal digestion and performance and profitability of production
Detection of a gut health problem at an early stage benefits the poultry industry through reducing cost of poor enteric health and associated compromised performance. This will allow rapid intervention to address the issue through management strategies, feed additives or seeking veterinary advice
In quest of suitable biomarkers of intestinal barrier function across species, there is a consensus that a suite of multiple biomarkers is superior to any single one to represent the status of a gut integrity related issue [5, 56]
Summary
Maintaining and improving gut health is fundamentally important as the gut supports optimal digestion and performance and profitability of production. Managing gut health through barrier function is regarded as a new frontier for disease prevention across different species [1]. Considerable research has been done on improving animal performance and gut health through various nutritional approaches. Few objective measures have been identified that could relate to the functionality of the intestinal barrier and detection of inflammation. Disruption of tight junction proteins, alteration in the mucus layer or changes in proliferation of epithelial cells could compromise gut integrity, increase bacterial translocation and eventually cause inflammation. Few biomarkers, related to gut permeability and inflammation, have been identified that could be non-invasive, simple and field-relevant. There have been very recent efforts to identify biomarkers of gut barrier function based on pathogenic and necrotising agents [4]. Intestinal contents, including from the colon, have been used as a proxy to excreta [4]
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