Effects of partial and complete replacement of freshwater shrimp meal (Caridinea niloticus Roux) with a mixture of plant protein sources on growth performance of Nile tilapia (Oreochromis niloticus L.) in fertilized ponds David M Liti 1 , Herwig Waidbacher 2 , Michael Straif 2 , Raphael K Mbaluka 3 , Jonathan M Munguti 4 & Mark M Kyenze 4 1 Department of Biological Sciences, Moi University, Eldoret, Kenya 2 Department of Water, Atmosphere & Environment, BOKU University of Natural Resources & Applied Life Sciences,Vienna, Austria 3 Department of Fisheries, Sagana Station, Sagana, Kenya 4 Kenya Marine & Fisheries Research Institute, Sangoro Aquaculture Station, PAP-Onditi Kisumu, Kenya Correspondence: D M Liti, Department of Biological Sciences, Moi University, PO Box1125, Eldoret, Kenya. E-mail: d __ liti@yahoo.co.uk Abstract Despite the well-documented herbivorous food ha- bits, commercial feeds for production of Oreochromis niloticus usually contain between 7% and 15% ani- mal protein. However, animal protein feedstu¡s are expensive, hence the need to search for cost-e¡ective alternatives in plant-protein sources. Such alterna- tives are probably more e¡ective in semi-intensive systems where natural pond food forms part of the diet. This study evaluated the performance of O. nilo- ticus after feeding diets in which fresh shrimp meal (SM) was gradually replaced by a mixture of plant- protein sources in fertilized ponds. Three isonitrone- genous (24% crude protein) diets containing12 (con- trol), 6% and 0% SM were fed to three groups of O. niloticus in four replicates per group for 250 days. Fish were fed daily at 2% body weight and sampled monthly to monitor growth and make feed adjust- ments. Growth, yields, survival and feed conversion ratio were not signi¢cantly di¡erent ( P40.05) among treatments. Growth of males was double that of fe- males, while the sex ratio was skewed towards fe- males. Although complete substitution of SM by plant protein did not a¡ect the growth of tilapia, pro- duction cost was reduced by 36%. In conclusion, an- imal protein is not required in diets for production of O. niloticus in fertilized ponds. Keywords: Oreochromis niloticus , cottonseed, wheat bran, semi-intensive, shrimp meal Introduction Nile tilapia ( Oreochromis niloticus L.) is one of the most important species among the commercially farmed tilapias. Under natural conditions, the adults of this species consume large quantities of plant materials, which are largely dominated by live algae, detritus and the associated bacteria (Moriarty 1973; Demp- ster, Beveridge & Baird 1993). However, despite the well-documented herbivory in O. niloticus , commer- cial diets for production in both intensive and semi- intensive system usually contain between 7% and 15% of animal protein, and are usually nutritionally complete, irrespective of the availability of natural pond food (Teichert-Cordington, Popma & Lovshin 1997). Among the most commonly tested animal feedstu¡s in tilapia feeds are ¢sh meal (Wu, Chung, Lin, Chen & Huang 2004) and shrimp meal (El-Sayed 1998; Liti, Cherop, Munguti & Chhorn 2005). These feedstu¡s have good palatability and high nutritional quality. Nevertheless, they are expensive and not al- ways readily available in some countries like Kenya, hence making tilapia feeds and production expensive. Aquaculture Research, 2006, 37, 477^483 doi: 10.1111/j.1365-2109.2006.01450.x r 2006 The Authors. Journal Compilation r 2006 Blackwell Publishing Ltd 477