Nutritional Evaluation of Rhizoclonium riparium var implexum Meal to Replace Soybean in the Diet of Nile Tilapia Fry

A study was conducted to evaluate the potential of crinkle grass Rhizoclonium riparium var implexum meal (RM) as a substitute for soybean in the diet of sex-reversed Nile tilapia Oreochromis niloticus fry. Four experimental diets were prepared containing various inclusion rates of RM at 0% (Diet 1), 4.2% (Diet 2), 8.4% RM (Diet 3) and 12.6% (Diet 4) equivalent to 0%, 15%, 30% and 45% replacement of soybean meal, respectively. Results showed that Diet 4 resulted in significantly higher final average body weight (FABW), weight gain (WG), protein efficiency ratio (PER), and better feed conversion ratio (FCR) than Diet 1. Diets 2 and 3 resulted in statistically similar responses to those of both Diets 1 and 4. Specific growth rate (SGR) was not affected by the dietary treatments. Dietary proximate compositions were correlated with the performance indices. This study showed that Rhizoclonium riparium var. implexum meal could be included in the diet of Nile tilapia up to 12.6%, equivalent to 45% soybean meal replacement. This could be an important cost-effective measure for intensive culture of tilapia.