Expression of selected genes encoding mechanistic pathways, nutrient and amino acid transporters in jejunum and ileum of broiler chickens fed a reduced protein diet supplemented with arginine, glutamine and glycine under stress stimulated by dexamethasone

Sensitivity of broiler performance, organ weights and plasma constituents to amino acid supplementation and reused litter exposure using ideal protein-formulated rations

Effects of amino acid supplementation to ideal protein (IP) formulated rations were investigated on growth performance, plasma metabolites and organ weights of broilers placed on 100% recycled (reused) litter. Day-old Ross308 male broilers were raised on either clean or reused litter and fed for three weeks on one of five isoenergetic diets, where an IP-based control diet (C) was compared with diets containing threonine (T) or arginine (A) at 25% above requirements, or with 1% supplemented glutamine (G), or with each amino acid added (TAG). Litter and diet treatments did not strongly interact on outcomes. Reused litter placement resulted in greater weight gain, smaller feed conversion ratio and heavier bursal weights (P < 0.05) compared to clean litter placement. Relative to C and T birds, TAG birds reduced weight gain and feed intake (P < 0.05). Plasma uric acid levels in G birds were greater than in C, T and A birds (P < 0.001). Collectively, since the outcomes of placement on reused litter increased performance and the control diet was IP formulated, the absence of increased growth performance in response to amino acid supplementation would be consistent with amino acids tested being excess to requirements.

Current experimental models, assessment and dietary modulations of intestinal permeability in broiler chickens

Maintaining and optimising the intestinal barrier (IB) function in poultry has important implications for the health and performance of the birds. As a key aspect of the IB, intestinal permeability (IP) is mainly controlled by complex junctional proteins called tight junction proteins (TJ) that link enterocytes together. The disruption of TJ is associated with increased gut leakage with possible subsequent implications for bacterial translocation, intestinal inflammation, compromised health and performance of the birds. Despite considerable data being available for other species, research on IP in broiler chickens and in general avian species is still an understudied topic. This paper reviews the available literature with a specific focus on IP in broiler chickens with consideration given to practical factors affecting the IP, current assessment methods, markers and nutritional modulation of IP. Several experimental models to induce gut leakage are discussed including pathogens, rye-based diets, feed deprivation and stress-inducing agents such as exogenous glucocorticoids and heat stress. Although various markers including fluorescein isothiocyanate dextran, expression of TJ and bacterial translocation have been widely utilized to study IP, recent studies have identified a number of excreta biomarkers to evaluate intestinal integrity, in particular non-invasive IP. Although the research on various nutrients and feed additives to potentially modulate IP is still at an early stage, the most promising outcomes are anticipated for probiotics, prebiotics, amino acids and those feed ingredients, nutrients and additives with anti-inflammatory properties. Considerable research gaps are identified for the mechanistic mode of action of various nutrients to influence IP under different experimental models. The modulation of IP through various strategies (i.e. nutritional manipulation of diet) may be regarded as a new frontier for disease prevention and improving the health and performance of poultry particularly in an antibiotic-free production system.

Intestinal Barrier Function and Performance of Broiler Chickens Fed Additional Arginine, Combination of Arginine and Glutamine or an Amino Acid-Based Solution

Two experiments were conducted to investigate the effect of arginine (Arg); the combination of Arg and glutamine (Gln); as well as an amino acid-based solution (MIX) containing Arg, Gln, threonine (Thr), and grape extract, on performance, intestinal permeability, and expression of selected mechanistic genes. Using 240 male Ross 308 off-sex broiler chickens, four experimental treatments were replicated six times with 10 birds per replicate. The experimental treatments included 5 g/kg Arg, 2.5 g/kg Arg and 2.5 g/kg Gln, and 1 g/kg MIX added to a basal diet as control. In the second study, the four dietary treatments were then given to 24 birds with or without a synthetic glucocorticoid, dexamethasone (DEX), as a gut dysfunction model. Feed conversion ratio was improved by all the supplemented treatments from day 7 to 35 of age (p < 0.001). DEX injections increased (p < 0.001) the intestinal permeability in all treatments, which tended to be reversed by Arg or MIX. Additional Arg, Arg-Gln, and MIX suppressed (p < 0.05) the overexpression of IL-1β generated by DEX. Feeding birds with MIX treatment increased (p < 0.05) expression of SGLT-1 and glutathione synthetase. In conclusion, tested amino acid supplements were effective in improving feed efficiency and restraining intestinal inflammation caused by DEX through IL-1β pathway.