A Novel in Vitro Poultry Model to Compare Release Kinetics of (un)protected Butyrate

The gastrointestinal (GIT) segment wherein dietary additives, such as butyrate, are released may influence their observed efficacy. Release kinetics are influenced by pH, gastric and enteric motility, retention time in the different GIT segments and enzymes concentration. Unfortunately, none of the available in vitro poultry model mimics accurately these conditions. As a consequence, a novel in vitro poultry GIT model was developed to compare the release kinetics of commercially available butyrate formulations. Four fat-embedded butyrate matrices originating from three suppliers as well as tributyrin, the triglyceride of butyrate, were evaluated in a three-step (pre-gastric, gastric and enteric) in vitro digestion procedure. Aliquots were drawn at 5 stages of digestion representing the end of the crop, proventriculusgizzard, duodenum, jejunum and ileum. The percentage of the initial butyrate dose solubilized was calculated for each stage. Significant differences were found among formulations for each digestion stage (P < 0.001). Half of the fatembedded butyrate matrices showed a sustained release profile, while the other released all their content in the preenteric regions. Tributyrin had a release profile targeting enteric segments. Results of this study indicate that despite almost identical visual appearance, release kinetics can vary significantly among butyrate derivatives. Such variations can possibly explain the inconsistency of the bird’s growth response to dietary butyrate supplementation as shown in literature.