Influence of the corn form in the diet and length of fasting before slaughter on the performance of overfed mule ducks.

The aim of this trial was to study the effect of the corn form fed during the overfeeding period and of the length of the fasting (LF) before slaughter on the performance of overfed mule ducks. A total of 180 ducks were distributed into 9 groups of 20 birds each, according to a 3 × 3 factorial design that differed according to the LF (9, 12, or 15 h) and the ratio of whole corn/corn flour in the overfeeding diet (OD): constant ratio of 30/70 [C diet]; progressive change from 0/100 to 30/70 [P diet]; or constant ratio of 0/100 [F diet]). At the end of the overfeeding period, the birds were slaughtered to measure the weight and chemical composition of the fatty liver. No significant interaction between the OD and LF was observed. The fatty liver weight was higher (+8%; P = 0.031) in the ducks fed the P diet than 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 than in those slaughtered after 15 h of fasting, The weight of fatty liver of birds slaughtered after 12 h was intermediate (711 g; P < 0.05). The foie gras fat loss during cooking (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 slaughtered after 9 h of fasting than in the other 2 groups. In conclusion, the present results suggest that (i) incorporating whole corn in the OD at a constant or increasing rate up to 30% significantly improves the performance of overfed mule ducks, and (ii) the shorter the fasting time is, the greater the weight and the quality of the foie gras will be.