Partial and full substitution of fish meal and soybean meal by canola meal in diets for genetically improved farmed tilapia (O. niloticus): Growth performance, carcass composition, serum biochemistry, immune response, and intestine histology

The study was designed to assess the effects of partial or full replacement of fish meal (FM) and soy bean meal (SBM) with canola meal (CM) on growth performance, health status, and cost benefit ratio of genetically improved farmed tilapia, Oreochromis niloticus. Fish (mean body weight 4.67 ± 0.07 g) were fed with five isonitrogenous (crude protein 396 g kg−1) diets: D I was set as the control; D II, D III, D IV, and D V were supplemented with CM at 25%, 50%, 75%, and 100% respectively. After 16 weeks of feeding, the optimum CM (%) for growth performance, feed utilization, carcass composition, and body indexes of O. niloticus were predicted at D III (P < 0.05). Also, the following linear regression equation was acquired for weight gain versus CM (%) in diets: Y = −2.542x + 23.232; R2 = 0.9474. The survival rate remained unaffected among all groups. Serum total protein, albumin content, and lysozyme activity increased in D I, D II, and D III; activity of liver functioning enzymes (SGPT and SGOT), triglycerides, total cholesterol, low-density lipoprotein-cholesterol, blood urea nitrogen, and creatinine level were elevated in groups D IV and D V (P < 0.05). Also, a significantly increased degree of variation and Uran’s pooled score were measured in intestine histology with increasing levels of CM supplementation (P < 0.05). Additionally, the optimum unitary feeding cost (UFC) was obtained in group D III (P < 0.05) along with polynomial equation: Y = 9.8 × 2– 47.39x + 176.44; R2 = 0.9674 between UFC and CM (%) in diets. Thus, FM and SBM could be replaced by CM up to 50% without compromising production, health status, and cost benefit for O. niloticus culture.