Importance of release location on the mode of action of butyrate derivatives in the avian gastrointestinal tract

Abstract

In the field of animal nutrition, butyrate is used as a zootechnical ingredient and can be used as an unprotected salt or in the form of protected derivatives such as butyrate glycerides or butyrate-loaded matrices. Dietary butyrate supplementation has been shown to improve growth performance and resilience of broiler chickens through distinct mechanisms, operating on both eukaryotic and prokaryotic cells. Firstly, butyrate influences endogenous avian cells in multiple ways: it is an agonist of free-fatty acid receptors, an inhibitor of pro-inflammatory pathways, an epigenetic modulating agent and acts as an energy source. Secondly, butyrate influences the microbiota residing in the avian gastrointestinal tract (GIT) as a result of its bacteriostatic properties. The responses, e.g. changes in growth performance, gut morphology, carcass traits or nutrient digestibility of chickens, to dietary butyrate supplementation are inconsistent with factors such as additive inclusion level, diet composition, age and health status of the bird modulating the effects of butyrate and its derivatives. For many derivatives, the precise GIT segment wherein butyrate is released is unclear. Release location may affect the observed responses to butyrate given the diversity of cell types and pH conditions encountered throughout the gastrointestinal tract of poultry, and the differences in microbiota composition in the different gut segments. As a consequence, our understanding of the mode of action of butyrate is hampered. Characterisation of existing derivatives and development of targeted-release formulations are, therefore, important to gain insight in the different physiological effects butyrate can elicit in broiler chickens

Effect of sodium butyrate on performance, immune status, microarchitecture of small intestinal mucosa and lymphoid organs in broiler chickens

“…The variability in FCR between control and the treatment groups is due to unidentified factors, however, it is assumed that better performance may be due to the creation of the acidic environment in the gut after SB consumption [3], which in turns minimizes the load of pathogens [10]. Average weekly feed intake was noted higher (p<0.05) in both SB supplemented groups compared to ZnB and control.…”

Butyrate in broiler diets : impact of butyrate presence in distinct gastrointestinal tract segments on digestive function, microbiota composition and immune responses

“…Increased butyrate concentration in the proximal GIT of birds fed UP, TB or FCB additives have already been reported elsewhere . The release profile of UP and FCB are consistent with the intrinsic properties of these products: UP is quickly absorbed in the proventriculus while FCB provides only a partial protection against gastric absorption (Moquet et al, 2016b). Tributyrin is, however, supposed to only be released in the proximal small intestine under the action of pancreatic lipase (Moquet et al, 2016b).…”

“…Butyrate may have limited effects on immunity when delivered in the crop, proventriculus and gizzard, because these locations are sparsely populated with immune cells . When present in these proximal GIT segments, butyrate cannot reach distally located immune cells due to simple, non-ionic diffusion in the proventriculus (Moquet et al, 2016b). Hence, butyrate has to be delivered beyond the proventriculus to reach the dense immune cells populations harboured by the small and large intestine.…”

“…injections of the potent NF-κB inducer E. coli lipopolysaccharide (LPS) on growth of broilers . The positive effect of dietary butyrate supplementation on growth performance of broilers may, therefore, be partly attributable to its anti-inflammatory properties (Moquet et al, 2016b).…”

“…Immunomodulatory properties of butyrate presumably vary depending on the GIT segment wherein the molecule is present because of metabolic differences among cell types along the avian GIT (Moquet et al, 2016b). Dietary supplementation with butyrate additives (e.g., unprotected sodium salt, tributyrin or fat coated butyrate) can have markedly different butyrate release patterns allowing contrasts in butyrate concentration in the digesta of broilers until the end of the small intestine to be created .…”