The effect of the feeding regime of mule ducks on loading of fishponds with organic matter in integrated fish-cum-duck technology was studied at theInstitute of Fisheries and Aquaculture – Plovdiv. The stocking density of the ducklings was 340 pcs.ha-1. The coefficient of loading (Ì) was used for establishing the pond loading: where N is the mean number of ducks in the rotation; t – rotation length in days; W – average live weight of theducks for the growing period, kg; 96 g – the amount of the manure released for a day by one duck per kg of live weight ; P – pond surface area,ha; r – relative stay of the ducks in water out of the active time of days.Two regimes of feeding the mule ducks were studied. It was establishedthat when fed on a balanced mixture, the mule ducks spent the bigger part of the day on land, as a result of which during the period of the study(40 days) the manure inserted in the pond amounted to 74.7 kg.ha-1. Substituting 50 % of the mixture with wheat, maize or sunflower groats(preserving the energy and protein levels), led to prolonging the average length of stay of the mule ducks in the pond almost 8 times. Due to themore significant differences in the time spent in the pond during the last ten-day periods, the manure released into water increased by morethan 10 times, although the live weight in all the periods was lower compared to the first variant.