Natural plant bioactive compounds (PBC) have recently been explored as feed additives to
improve productivity, health and welfare of poultry following ban or restriction of in-feed antibiotic
use. Depending upon the types of PBC, they possess antimicrobial, digestive enzyme secretion stimulation,
antioxidant and many pharmacological properties, which are responsible for beneficial effects in
poultry production. Moreover, they may also improve the intestinal barrier function and nutrient
transport. In this review, the effects of different PBC on the barrier function, permeability of intestinal
epithelia and their mechanism of actions are discussed, focusing on poultry feeding. Dietary PBC may
regulate intestinal barrier function through several molecular mechanisms by interacting with different
metabolic cascades and cellular transcription signals, which may then modulate expressions of genes
and their proteins in the tight junction (e.g., claudins, occludin and junctional adhesion molecules), adherens
junction (e.g., E-cadherin), other intercellular junctional proteins (e.g., zonula occludens and
catenins), and regulatory proteins (e.g., kinases). Interactive effects of PBC on immunomodulation via
expressions of several cytokines, chemokines, complement components, pattern recognition receptors
and their transcription factors and cellular immune system, and alteration of mucin gene expressions
and goblet cell abundances in the intestine may change barrier functions. The effects of PBC are not
consistent among the studies depending upon the type and dose of PBC, physiological conditions and
parts of the intestine in chickens. An effective concentration in diets and specific molecular mechanisms
of PBC need to be elucidated to understand intestinal barrier functionality in a better way in
poultry feeding.
