Role of butyrate as part of milk replacer and starter diet on intestinal development in pre-weaned calves. A systematic review

It is well known that the timely development of the rumen is important to encourage intake and degradation of solid feeds. As a result, various studies have focused on feeding strategies to accelerate rumen development. However, the small intestine which is the site for digestion of liquid feeds and nutrient absorption in calves has received little attention. Growing evidence suggests that the exogenous inclusion of butyrate into the starter mixture (SM), milk and milk replacer (MR) of calves could hasten the development of the small and large intestines. Therefore, this paper is aimed at analyzing the few studies that investigated the efficacy of butyrate inclusion into milk/MR or starter mixture (SM) on intestinal development in pre-weaned calves. The two forms of butyrate discussed in this review are encapsulated and non-encapsulated. The encapsulated butyrate is produced by embedding the butyrate salts within a lipid matrix to reduce the action of rumen fermentation on the butyrate salts until it enters the duodenum where it stimulates the development of the small intestine. On the other hand, the inclusion of non-encapsulated butyrate into MR/milk made it possible for the butyrate salts to escape the ruminal environment via the oesophageal groove, which is activated in young calves during suckling. Sodium butyrate exerts its actions in the rumen and intestine through the upregulation of genes associated with cellular proliferation and downregulation of apoptotic genes which in turn accelerates the cell cycle. However, the efficacy of butyrate on the cell cycle is influenced by the concentration of butyrate, the phase of the cell division, as well as other indirect factors. Future researchers can employ transcriptomics to study the genes associated with cellular proliferation and apoptosis in the small and large intestines of calves.