Nguyen Thi Kim Kang et al., 2004. Livest. Res. Rural Dev., 16 (8): 56

Two trials were carried out to determine the effect of replacing roasted soya beans with broken rice and duckweed (DW) in diets for growing (Tau Vang) chickens. The first trial was done in confinement at the experimental farm of Cantho University; the second was on farms in Long Hoa village in a scavenging system. The on-station trial was a completely randomized design with 5 dietary treatments and 3 replicates. The control diet was mixed broken rice and roasted soya beans only (SB100); the other four diets had duckweed available ad libitum, with soya beans at levels of 0, 25, 50 and 75 of the SB100 diet (SB0DW, SB25DW, SB50DW, SB75DW, respectively), fed to growing chickens from 5 to 15 weeks of age. The proportion of dietary protein contributed by duckweed increased linearly (R 2=0.96) as the content of soya beans in the concentrate was reduced. Total DM intake and live weight gain showed a positive curvilinear relationship with the proportion of dietary protein derived from duckweed. DM feed conversion was equally related with the proportion of dietary protein derived from duckweed. Optimum values were obtained with 75% replacement of roasted soya beans protein by duckweed. The meat from chickens fed duckweed had a more intense yellow color than that from birds on the soya bean meal control diet. Feeding fresh duckweed to local growing chickens resulted in decreased feed costs compared to the diet with 100% soya beans, especially when 100% and 75% of the soya beans was replaced by broken rice and fresh duckweed. The on-farm trial was a completely randomized design with 3 treatments and 4 replications (farms). The SB25 diet from the on-station trial was selected as the basal diet and given to all experimental groups. There were in total 60 chickens from 5 weeks of age on each farm divided into 3 groups of 20. Two groups were allowed to scavenge in the gardens, with or without a duckweed supplement (SCDW and SC), and one group was confined (CFDW) and given duckweed ad-libitum. There were no differences in growth performance among the treatments. The highest economic benefits were on the SCDW diet.