Replacement of Fishmeal by Poultry By-Product Meal, Supplemented with Lysine, Methionine, and Threonine, in Diets for Fry of Nile Tilapia (Oreochromis niloticus)

The effects of replacing commercial fishmeal by poultry by-product meal in practical diets for Nile tilapia fry, Oreochromis niloticus, were investigated. Triplicate groups of 20 fish (0.879±0.09 g) were fed one of five isonitrogenous (34% crude protein), isolipidic (9% crude lipid), and isoenergetic (3570 kcal/kg) diets in which 0% (control), 25%, 50%, 75%, or 100% of the fishmeal protein was replaced by poultry by-product meal protein. The poultry by-product diets were supplemented with lysine, methionine, and threonine to match the amino acid profiles of the control diet. The fish were fed to apparent satiation three times daily for 12 weeks in 65-l glass aquaria. Fish growth increased as the poultry by-product meal content increased up to 50%, then severely decreased at the replacement levels of 75% and 100%. The protein efficiency ratio dropped and feed conversion ratio rose at the same levels. Whole body composition, survival rate, condition factor, hepatosomatic index, and viscerosomatic index were not significantly affected by the dietary treatment (p>0.05). Protein, lipid, and energy digestibility coefficients decreased as the poultry by-product meal content increased, and the best digestibility values were obtained in fish fed the 50% replacement diet. Results indicate that up to 50% of fishmeal protein can be replaced by poultry by-product meal protein supplemented with lysine, methionine, and threonine in diets for Nile tilapia fry without adverse effects on growth, feed utilization, body composition, or digestibility of nutrients.