Munguti et al., 2009. Livest. Res. Rural Dev., 21 (8): 129

The effects of substituting hydrolysed feather meal (HFM) for freshwater shrimp meal (FSM; Caridina nilotica, Roux) on growth, digestibility and survival in Nile tilapia (Oreochromis niloticus L.) were evaluated under laboratory and practical culture conditions. Fingerlings with mean ranges of 26.0-26.5 and 35.4-37.0 g were held indoor in aquaria with recirculating water, and in cages that were installed in 800 m2 fertilized pond, respectively. Five isocaloric (12.3 kJ g-1) diets, containing between 28.5 and 31.0% of crude protein, were prepared by gradually substituting HFM for FSM at rates of 0, 25, 50, 75 and 100% and fed to fish in aquaria; tilapia in cages were fed diets at substitution levels 0, 50 and 100%. All fish were fed at 10% of body weight day-1 in three replicates for 84 days. Results indicated that substitution of HFM for FSM at levels above 50% led to significant (P<0.05) growth reductions in aquaria. However, even 100% substitution rate did not significantly (P>0.05) affect growth of fish in the cages. In both experiments, survival was similar among treatments, but apparent protein digestibility decreased with increasing levels of HFM in the diet. In conclusion, at least 50% substitution of HFM for FSM is possible in semi-intensive culture of Oreochromis niloticus, where natural food is available and where moderate growth performance levels may be accepted.