Negative consequences of reduced protein diets supplemented with synthetic amino acids for performance,intestinal barrier function,and caecal microbiota composition of broiler chickens

The consequences of feeding broiler chickens with reduced protein(RP)diets for gut health and barrier function are not well understood.This study was performed to elucidate the effect of reducing dietary protein and source of protein on gut health and performance parameters.Four experimental diets included 2 control diets with standard protein levels either containing meat and bone meal(CMBM)or an all-vegetable diet(CVEG),a medium RP diet(17.5%in growers and 16.5%in finisher),and a severe RP diet(15.6%in grower and 14.6%in finisher).Off-sex Ross 308 birds were assigned to each of the 4 diets and performance measurements were taken from d 7 to 42 post-hatch.Each diet was replicated 8 times(10 birds per replicate).A challenge study was conducted on additional 96 broilers(24 birds per diet)from d 13 to 21.Half of the birds in each dietary treatment were challenged by dexamethasone(DEX)to induce a leaky gut.Feeding birds with RP diets decreased weight gain(P<0.0001)and increased feed conversion ratio(P<0.0001)from d 7 to 42 compared with control diets.There was no difference be-tween CVEG and CMBM control diets for any parameter.The diet containing 15.6%protein increased(P<0.05)intestinal permeability independent of the DEX challenge.Gene expression of claudin-3 was downregulated(P<0.05)in birds fed 15.6%protein.There was a significant interaction between diet and DEX(P<0.05)and both RP diets(17.5%and 15.6%)downregulated claudin-2 expression in DEX-challenged birds.The overall composition of the caecal microbiota was affected in birds fed 15.6%pro-tein having a significantly lower richness of microbiota in both sham and DEX-injected birds.Proteo-bacteria was the main phylum driving the differences in birds fed 15.6%protein.At the family level,Bifidobacteriaceae,Unclassified Bifidobacteriales,Enterococcaceae,Enterobacteriaceae,and Lachnospir-aceae were the main taxa in birds fed 15.6%protein.Despite supplementation of synthetic amino acids,severe reduction of dietary protein compromised performance and intestinal health parameters in broilers,evidenced by differential mRNA expression of tight junction proteins,higher permeability,and changes in caecal microbiota composition.

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 impli-cations 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.

Balanced nutrient density for broiler chickens using a range of digestible lysine-to-metabolizable energy ratios and nutrient density:Growth performance,nutrient utilisation and apparent metabolizable energy

Currently,specific nutrient concentration,metabolizable energy(ME)and digestible amino acids are used as feed formulation criteria.A balanced nutrient density(BND)concept based on 2 criteria of nutrient density and balanced amino acids-to-ME ratio may offer more flexibility in optimisation of profit in formulation of diets compared with current formulation based on set values per unit of feed mass.A total of 672 one-d-old off-sex male Ross 308 broiler chickens were used across two 42-d performance trials in a 3×2 factorial arrangement of treatments with each diet replicated 8 times(14 birds per replicate).The experimental factors were 2 nutrient density levels(low[LD]and high[HD])and 3 digestible lysine-to-ME ratios(DLYS:ME;low,medium,and high).Low density diets had ME of 2,876 and 3,023 kcal/kg for starter and finisher,respectively,while values for HD diets were 3,169 and 3,315 kcal/kg with proportionally higher non-nitrogenated nutrients.Separate digestibility and apparent metaboliz-able energy(AME)assays were conducted at d 21 and 42.Digestibility assays at d 7 were conducted on birds used for performance trials.Regardless of the diet density,birds fed low DLYS:ME had a lower(P<0.01)feed intake(d 0 to 42)than medium and high DLYS:ME.Without interaction,birds fed low and medium DLYS:ME had a similar body weight gain being the heaviest while birds low DLYS:ME were the lightest.By an interaction(P<0.05),the highest overall FCR value was observed for birds fed LD×low DLYS:ME and improved linearly when DLYS:ME increased to the highest level reaching a limit for birds fed HD×medium DLYS:ME.Calorie conversion linearly decreased(P<0.001)with increments in DLYS:ME.Jejunal and ileal starch and protein digestibility were affected on d 21 and 42 but not on d 7 of age.Given the independence of response on BW and feed consumption,the use of BND as a flexible system in diet formulations has the potential to enable more accurate formulation for optimisation of growth performance of broiler chickens.