Protein concentrate of Ulva intestinalis (Chlorophyta, Ulvaceae) could replace soybean meal in the diet of Oreochromis niloticus fry

Abstract

An experiment was conducted to evaluate the effects of replacing soybean meal with the protein concentrate of Ulva intestinalis (UPC) in the diet of juvenile Nile tilapia, Oreochromis niloticus. Four experimental diets were formulated to replace 0, 15, 30 or 45% of soybean meal by weight and were fed to group of fish for 90 days. Results showed that survival rates were high and independent of dietary treatment. Feed intake decreased as level of inclusion of UPC increased. Food conversion ratios of Nile tilapia fry fed the experimental diets were all statistically similar. Weight gain and specific growth rate of Nile tilapia fry fed with the diet containing 15% replacement was statistically similar with those of fish fed with the control diet. Thus, U. intestinalis protein concentrate could replace 15% by weight of the imported soybean meal without negatively affecting food conversion ratio, weight gain and specific growth rate; this substitution could mean slightly cheaper formulated diets for the Nile tilapia fry and fingerlings.