Applications of new functions for inducing host defense peptides and synergy sterilization of medium chain fatty acids in substituting in-feed antibiotics

Developing alternatives to classic antibiotic growth promoters (AGPs) in feed industry has been being urgently called but an individual alternative is unlikely to embody all functions of classic antibiotics. One potential solution is to select multiple products which work synergistically and a comprehensive solution. This review mainly discuss recent advances in medium-chain fatty acids' (MCFAs) roles as an important component of the mammalian innate immune defense system, new functions for inducing host defense peptides and synergy sterilizations with edible essential oils or edible organic acids, and these multifaceted functions' application potential to solve their technological challenges in substituting in-feed antibiotics such as unpleasant odor, low solubility, poor chemical stability and volatile nature. The review highlights that MCFAs are originally an important component of innate immune defense system in mammalian breast milk, skin and mucosa, and also induce host defense peptide expression in human, pig, chicken, rabbit and mice, which are beneficial supplement to their previously found in vitro antimicrobial functions. It is concluded that using encapsulated MCFAs combinations with edible essential oils or organic acids would be one preferred solution to overcome their technological challenges in substituting in-feed antibiotics such as unpleasant odor, low solubility, poor chemical stability and volatile nature, and also have the relative difficulty with which bacteria develop resistance. However, the basic data related to combinations of various alternatives and the underlying mechanisms remain lacking.