The aim of this trial was to study theeffect of the corn form fed during the overfeeding periodand of the length of the fasting (LF) before slaughter onthe performance of overfed mule ducks. A total of 180ducks were distributed into 9 groups of 20 birds each,according to a 3×3 factorial design that differed ac-cording to the LF (9, 12, or 15 h) and the ratio of wholecorn/corn flour in the overfeeding diet (OD): constantratio of 30/70 [C diet]; progressive change from 0/100to 30/70 [P diet]; or constant ratio of 0/100 [F diet]). Atthe end of the overfeeding period, the birds were slaugh-tered to measure the weight and chemical compositionof the fatty liver. No significant interaction between theOD and LF was observed. The fatty liver weight washigher (+8%;P= 0.031) in the ducks fed the P dietthan those fed the F diet. The ones fed the C diet were intermediate (709 g). The fatty liver weight was heavier(+7%) in the ducks slaughtered after 9 h of fasting thanin those slaughtered after 15 h of fasting, The weightof fatty liver of birds slaughtered after 12 h was inter-mediate (711 g;P<0.05). Thefoie grasfat loss duringcooking (20% vs. 27%;P= 0.003), DM (68.13% vs.69.3%;P= 0.021), and ash content (0.40% vs. 0.36%;P= 0.010) were lower in the group of ducks slaugh-tered after 9 h of fasting than in the other 2 groups. Inconclusion, the present results suggest that (i) incorpo-rating whole corn in the OD at a constant or increasingrate up to 30% significantly improves the performanceof overfed mule ducks, and (ii) the shorter the fastingtime is, the greater the weight and the quality of thefoie graswill be.