Defatted and full-fat soybean meal as partial replacement for fishmeal in tilapia (Oreochromis niloticus × O. aureus) diets at low protein level.
The feasibility was assessed of partly replacing fish meal protein with protein from defatted soyabean meal or full-fat soyabean meal. The control diet contained blue whiting fish meal imported from Norway as the sole source of protein. Each test diet contained 24% protein and 11% lipid on an air-dry basis. The diets were of equal energy value, containing 395 kcal/100 g. Each diet was given to 3 groups of fish. The experiment was made in a closed rearing system with recirculated filtered water for 9 weeks. The weight gain (%), feed conversion ratio (FCR), protein efficiency ratio (PER) and protein digestibility for fish fed on diets in which 30% of fish meal protein was replaced by defatted soyabean meal or by full-fat soyabean meal were not significantly different from those of fish fed on the control diet. The results suggest that either defatted soyabean meal or full-fat soyabean meal can be used to replace 30% fish meal protein in a diet for Oreochromis niloticus × O. aureus fingerling hybrids when the dietary protein level is low (24%), at least for the first 9 weeks of feeding. Further study of the replacement value of soyabean meal protein for fish meal protein is thought necessary for the subsequent grow-out stage of tilapia.