Genetic parameters of traits related to hepatic lipid metabolism, carcass composition and products quality of overfed mule ducks were estimated on both parental lines of this hybrid: the “common duck” line for the maternal side and the “Muscovy” line for the paternal side. The originality of the statistical model was to include simultaneously the additive genetic effect of the common ducks and that of the Muscovy ducks, revealing a higher genetic determinism in common than in Muscovy. Plasma metabolic indicators (glucose, triglycerides and cholesterol contents) were heritable, in particular at the end of the overfeeding period, and heritabilities increased with the overfeeding stage. Carcass composition traits were highly heritable in the common line, with values ranging from 0.15 for liver weight, 0.21 for carcass weight and 0.25 for abdominal fat weight to 0.32 for breast muscle weight. Heritabilities of technological outputs were higher for the fatty liver (0.19 and 0.08 respectively on common and Muscovy sides for liver melting rate) than for the Pectoralis major muscle (between 0.02 and 0.05 on both parental sides for cooking losses). Fortunately, the processing industry is mainly facing problems in liver quality –such as too high melting rate- than in meat quality. The meat quality appraisal criteria such as texture and cooking losses), usually dependent on the pH and the falling speed of the pH, were also very lowly heritable. This study demonstrated that genetic determinism of meat quality and ability of over-feeding is not similar in the common population and in the Muscovy population: traits related to fattening, muscle development and body weights have heritabilities values from 2 to 4 times higher on the common line than on the Muscovy line, which is relevant for considering different selection strategies.