Effect of replacing soybean meal with cottonseed meal on growth, feed utilization, and hematological indexes for juvenile hybrid tilapia, Oreochromis niloticus × O. aureus

An 8-week feeding experiment was conducted to evaluate the effects of replacing soybean meal (SBM) with cottonseed meal (CSM) on growth, feed utilization, and hematological index of juvenile hybrid tilapia. Six isonitrogenous diets (containing ~ 32% crude protein) containing graded levels of cottonseed meal to replace soybean meal protein were fed to triplicate groups of fish. The diets were supplemented with lysine so that they were similar to the control diet. The results revealed that up to 60% of SBM could be replaced by CSM without causing a significant reduction in growth. Fish fed the diet highest in CSM had a significantly lower protein efficiency ratio and a significantly higher feed conversion ratio than fish fed the other diets. High survival was observed in all dietary treatments, and no significant difference among treatments was observed. The apparent digestibility coefficients (ADC) of dry matter and phosphorus significantly decreased with the increase of dietary CSM level, whereas the ADC of lipid was not affected by dietary treatment. The hepatosomatic index and condition factor were significantly affected by the replacement of SBM by CSM. No significant differences were detected in moisture, lipid, and ash content in whole body and muscle samples, but protein in whole body samples was significantly affected by CSM levels. Significant differences in hemoglobin, hematocrit, red blood cell, and white blood cell content were found in fish fed diets with different CSM levels. These results show that up to 33.76% CSM can be used to replace ~ 60% of SBM in diets for juvenile hybrid tilapia.