Circulating peptide YY shows no postprandial response and is unrelated to feeding behavior in zebra finches.

The regulation of feeding behavior, particularly the timely cessation of food intake, is essential for maintaining energy balance. In mammals, the gut-derived hormone peptide YY (PYY) plays an important role in short-term satiety signaling, with circulating concentrations increasing rapidly after meals to suppress further food intake. In non-mammalian vertebrates, however, the role of PYY in satiety signaling remains poorly understood. The aim of the present study was to test the hypothesis that circulating PYY functions as a short-term satiety signal in birds, analogous to its established role in mammals. We compared preprandial and postprandial circulating PYY concentrations in adult zebra finches (Taeniopygia guttata) that were either food-restricted for 20 days or fed ad libitum. In addition, we quantified feeding motivation, measured as latency to initiate feeding, and food consumption to assess whether variation in circulating PYY was associated with feeding behavior. Contrary to our predictions, circulating PYY concentrations did not increase following feeding, did not significantly differ between food-restricted and ad libitum birds, and were unrelated to either feeding latency or food consumption. Collectively, these findings fail to support the hypothesis that PYY functions as a conserved short-term satiety signal in zebra finches. Instead, our results suggest that the role of PYY in zebra finches may differ from the mammalian pattern and highlight the need for additional comparative studies in birds.