The feeding of waterfowl for fatty liver production is largely based on the use of completely pelleted feed. To reduce both the economic and environmental costs caused by transport and processing of feed and to respond to consumer demands for natural feeding systems, the use of whole grains has increased recently. The aim of this trial was to study the influence of 1) sequential feeding based on cereal grain and 2) cereal type (corn or triticale) during the finishing period on performance traits in male mule ducks. Present results suggest that a sequential feeding system modifies feeding behavior, growth, and body traits, and reduces feed intake during the finishing period (−6 and −10% for corn and triticale, respectively), but has no effect on performance during the overfeeding period. This system offers interesting prospects for a more sustainable rearing method, and the use of locally grown grains could reduce both the economic and environmental impacts of duck feeding.