Abstract
Three experimental diets, including fish meal replaced with different ratios (20%, 40% and 60%) of Ulva lactuca and a seaweed-free control diet were used to evaluate the effect of dietary seaweed incorporation on the growth performance, feed utilization and body composition of the Nile tilapia, Oreochromis niloticus. The experiment lasted for 12 weeks and the results of the growth indicators; final weight (FW), weight gain (WG), percentage of weight gain (WG%), daily growth rate (DGR) and specific growth rate (SGR) indicated no significant differences (P>0.05) between the fish on the control diet (C) and those on a diet with 20% U. lactuca (U20), despite the fact that an outstanding performance of fish growth was accomplished on the control diet. Furthermore, no significant differences among C and U20 for the feed conversion ratio (FCR) and protein efficiency ratio (PER) whereas the feed utilization efficiency, FCR and PER decreased significantly when the proportion of U. lactuca meal was increased to 40% and 60% (U40 and U60). Carcass and muscle composition showed a similarity between the various groups. Moisture, protein and ash content showed an increase in line with the increase in U. lactuca meal in the diets, but the reverse was observed for the lipid level. The present study observed that U. lactuca meal attained considerable performance for feeding the Nile tilapia at dietary inclusion levels up to 20% without undesirable effects on growth performance and feed utilization efficiency.