Abstract:Condensed molasses fermentation soluble (CMS) is a byproduct of production of lysine or monosodium glutamate. A feeding trial was conducted in outdoor fiberglass reinforced polyethylene tanks with fingerling Nile tilapia (Oreochromis niloticus) to investigate the feasibility of using CMS as a protein source replacement for defatted soybean meal (SBM) in a practical diet. The basal diet contained 9.9% fishmeal, 5.0% SBM and 33.3% defatted SBM as major protein sources providing for 32% dietary crude protein level in which the defatted SBM protein fraction was replaced by CMS protein from 0-100% at a 20% interval. There were total of six experimental diets, each diet was fed to triplicate groups of fish for 6 weeks. The results indicated that as CMS level increased, growth performance and feed efficiency decrease, and body ash content of the resulting fish increased, which could be attributed to higher ash and sodium content, lower energy, and more unbalanced amino acid profile in CMS than in defatted SBM. However, 20% protein replacement of defatted SBM by CMS did not make differences in growth performance, feed efficiency, and body composition of the resulting fish. Therefore, CMS can still be considered as a promising alternative protein source for partial substitute of soybean meal in the practical diet of tilapia.