Hyperphagia and hepatic lipid storage in ducks: an exploratory experimental model

This study aimed to investigate whether spontaneous hyperphagic behavior can be induced in mule ducks through a protocol combining feed restriction followed by 1-h concentrated meals and to assess the resulting hepatic metabolic responses. To achieve this, two protocols were tested. The first protocol initially demonstrated that a 5-day acclimation phase, consisting of alternating 23-h fasting periods and 1-h refeeding periods, was necessary to induce hyperphagia in ducks. Then, an increase in liver weight and glycogen content was measured up to 12 h after the substantial meal, before returning to baseline after 24 h, whereas total lipid levels remained unchanged. Based on these observations, a second protocol was designed to assess whether an additional meal provided 12 h after the last substantial meal could promote lipid storage in the liver. A significant increase in liver weight and glycogen content was measured after each 1-h meal, whereas total hepatic lipid content increased significantly after the last meal provided 12 h after the previous one. This was associated with an upregulation of genes involved in lipogenesis (FASN, SCD1, and ELOVL6) and carbohydrate oxidation (HK1), and a downregulation of a gene involved in lipid oxidation (ACSL1). Together, these results demonstrate for the first time that voluntary feeding alone can induce measurable hepatic lipid accumulation in mule ducks. This new protocol represents a valuable experimental model for the study of hepatic lipid metabolism in ducks and could contribute to the development of alternative strategies for liver fattening.NEW & NOTEWORTHY This study provides new insights into the physiological effects of a substantial voluntary meal on hepatic energy metabolism in the mule duck, a species for which information on this topic remains limited. Our findings show for the first time that hepatic lipid deposition can be induced through voluntary feeding, without the need for force-feeding. In the longer term, these results may support the development of alternative practices to force-feeding for foie gras production.