Fat coating of Ca butyrate results in extended butyrate release in the gastrointestinal tract of broilers

•Butyrate has been suggested as an alternative to antimicrobial growth promoters.•The major target of antimicrobial growth promoters is thought to be the small intestine.•However, uncoated butyrate is metabolized proximal to the small intestine.•Here we demonstrate that fat coating of butyrate results in a similar release pattern as the stomach passage indicator octanoic acid.•This suggests that fat coating of butyrate indeed results in targeting the intestines distal of the stomach.

Based on its described beneficial effects on small and large intestinal epithelium, butyrate can be a very good alternative to antimicrobial growth promoters. Effective dietary application requires coating because the majority of uncoated butyrate is purportedly absorbed before reaching the proximal small intestine. Several studies using different protocols reported varying stomach passage times in chickens. In the present study, we compared feeding uncoated vs. fat coated [1-13C] labeled Ca butyrate, and compared the effect of butyrate coating with [1-13C] labeled octanoic acid which is an established indicator of stomach passage. By monitoring 13CO2 expiration continuously, we show that the majority (about 80%) of uncoated Ca butyrate is oxidized proximally of the small intestine, and that base line levels were reached after 6 h. Fat coating of Ca butyrate resulted in reduced proximal oxidation (from about 80% to about 45%), and in an extended release pattern of 13CO2 from butyrate similar to that of octanoic acid, and that the return to base line levels was extended to 12 h. This indicated that fat coating of butyrate results in absorption along the entire intestinal tract in broilers, offering an explanation for the described beneficial effects as a growth promoter.