Effects of replacing corn with sorghum on the performance of overfed mule ducks

The aim of this trial was to study the effects of replacing yellow corn (C) with condensed tannin-free sorghum (S) during the finishing period (F period; age 53 to 79 d) and/or overfeeding period (O period; age 80 to 91 d) on the performance of overfed mule ducks. 192 ducks were divided into 4 groups (48 in each) differing in the cereal (yellow corn or sorghum) included in the diet given during the F and/or the O periods, using a 2 × 2 factorial arrangement of treatments : SS, SC, CS, CC. At the end of the O period, the birds were slaughtered after 10 h of fasting to measure foie gras and magret qualities. Mortality (1%; P > 0.05) and weight gain (2,030 g; P > 0.05) during the O period were similar in the 4 groups. At the end of the O period, birds overfed with sorghum had foie gras that was heavier (723 vs. 694 g in CS+SS vs. CC+SC, respectively; P < 0.05) and less yellow (24.40 vs. 38.59 for b* in CS+SS vs. CC+SC, respectively; P < 0.001) than birds overfed with corn. Fat loss during foie gras cooking was similar in the 4 groups (18%; P > 0.05), but the foie gras was less yellow in birds overfed with sorghum (14.84 vs. 26.01 for b* in CS+SS vs. CC+SC, respectively; P < 0.001). Weight of magret was similar in the 4 groups (491 g, P > 0.05) but the color of the breast muscle and skin of magret was less yellow in birds overfed with sorghum compared with corn (12.26 vs. 12.92 and 13.84 vs. 18.30 in CS+SS vs. CC+SC, respectively; P < 0.001). In conclusion, the replacement of yellow corn with sorghum during finishing and/or overfeeding is possible and useful in a mule duck foie gras production system because it increases foie gras weight without decreasing the weight of magret However, it changes the quality of the products, mainly their color.