The aim of the study is to better understand the mechanisms underlying the steatosis in birds. Twodimensional electrophoresis gels were performed in liver at different stages of steatosis in duck. Mule ducks were slaughtered after 0, 14 or 23 meals of force-feeding according to commercial conditions. T, Thirty-one proteic spots were differentially expressed between 2 or 3 durations of overfeeding: 3 spots were differentially expressed between the 3 times, 28 between 2 times. The identified proteins (17) could be regrouped into 5 categories: enzymes, traduction factor, proteins involved in cell structure, proteins with antioxidant properties, and proteins that can link calcium.