Cottonseed meal as a substitute for soybean meal in Nile tilapia diet

Abstract

This feeding trial was conducted to evaluate the effects of partial replacement of soybean meal by cottonseed meal and the effects of two feed processing methods, pelleting and extrusion, in Nile tilapia feeds. The cottonseed meal was solvent-processed and contained no amount of free gossypol and 0.0987% of total gossypol. The diets were formulated to contain 30% digestible protein and 3200kcal/kg digestible energy and the supplemental amino acids were added based on the ideal protein concept. In the experimental diets, soybean meal protein was gradually replaced by cottonseed meal protein (0, 12.5, 25 and 50%), which corresponded to 0, 8, 16 and 32% of inclusion of cottonseed meal in the diets, respectively. 192 Nile tilapia fingerlings with an average weight of 4.600.23g, were distributed in 32 200-L cylindrical net-tanks, on a recirculating water system and were fed to apparent satiation four times a day, during 95 days. The experiment was conducted in a 4x2 factorial, in a completely randomized design, with four replicates. After 95 days, no significant differences for growth performance and physiological responses of fish fed diets containing cottonseed meal in comparison to fish fed the diets based on soybean meal were observed. Cottonseed meal (0% free gossypol) can replace 50% of soybean meal protein in the diet (32% of inclusion level in the diet) of Nile tilapia if supplemented with synthetic lysine, without impared growth performance, hematology and intestinal morphology.