Postprandial dynamics of sensory receptor and neural mechanisms underlying feeding regulation in mule ducks

The gustatory system plays a central role in nutrient detection and feeding regulation in birds, yet the underlying molecular mechanisms in ducks remain poorly characterized. Here, we provide the first integrated analysis of nutrient detection pathways, from peripheral oral sensing to central brain integration, in mule ducks at 4 weeks of age. Nutritional status was confirmed via plasma free fatty acids and triglycerides. We quantified taste receptors mediating sweet (Taste Receptor type 1 member 1 and 3), bitter (Taste Receptor type 2 member 9 and 40), sour (Acid-Sensing Ion Channels), umami (Metabotropic Glutamate Receptors 3 and 4), and lipid (G Protein-coupled Receptor 119 and family C group 6 member A) perception, together with key calcium-signaling components involved in gustatory transduction (Stromal Interaction Molecule 1 and Calcium release-activated calcium modulator 2), across the tongue, palate, and oral floor mucosa. Serotonin (5-hydroxytryptamine, 5-HT) dynamics in these tissues were assessed as a peripheral neural readout. Feeding induced rapid, tissue-specific modulation of taste receptor and calcium-signaling gene expression, with the strongest effects consistently observed in the oral floor mucosa, likely reflecting species-specific oral anatomy and ingestion behavior. Postprandial feeding increased 5-HT levels in gustatory tissues. In contrast, hypothalamic neuropeptide expression remained largely unchanged, whereas central dopaminergic and serotonergic pathways exhibited feeding-dependent metabolic changes. Together, these findings reveal a dynamic peripheral gustatory system capable of detecting multiple nutrient classes and triggering rapid central neurochemical responses in ducks. This study provides a framework for understanding how oral nutrient detection interfaces with central feeding circuits and establishes a reference for developmental and nutritional studies targeting gustatory and neurochemical pathways in avian species.