Orange corn diet modulates Pekin duck cecal neurochemistry under normal and heat stress conditions

Heat stress (HS) drives changes in poultry gut health that negatively affect performance, behavior, foodborne pathogen carriage, among other factors. Little attention, however, has been directed towards the impact of HS on the duck intestinal tract. Intestinal concentrations of monoamine neurochemicals, which have been shown to be stress-responsive in several poultry species, play a variety of roles in mediating the effects of stress both locally in the gut and in overall physiology. Yet, the concentrations of neurochemicals and accompanying metabolic pathways in the duck intestine remain understudied. As an orange corn (OC) diet was previously shown in poultry to benefit welfare and performance, the present study sought to determine the impact of an OC versus a yellow corn (YC) diet on duck intestinal monoamine neurochemistry under thermoneutral and heat stress conditions. Male and female Pekin ducks were randomly assigned to a YC or OC diet, with each diet fed for 3 wks immediately before HS, and then continuing being fed during the 3 wks of cyclic HS exposure (35°C for 10h/d). Cecal tissue (CT) and luminal content (CC) were collected before the start of HS and then on the final day of the 3 wks of HS. Sex and feed type affected (p < 0.05) catecholamine and serotonin concentrations in ducks under thermoneutral and HS conditions. CT protein expression of monoamine oxidase-A and catechol-o-methyltransferase showed sex- and feed type-dependent changes (p < 0.05) only in ducks that underwent HS. DOPA-decarboxylase was affected (p < 0.05) under HS but not during constitutive conditions. The present study establishes that the duck intestinal tract is an abundant source of monoamine neurochemicals, and that key proteins involved in neurochemical metabolism are present in the duck ceca. These findings warrant the study of feed components as a tailorable strategy to potentially control stress at the gut-level. As enteric neurochemicals play critical roles in inflammation, foodborne pathogen colonization, and other production-relevant aspects in poultry, our findings highlight the importance of intestinal neurophysiology in the duck.