The effect of hydrolyzed protein, vitamin E and oxidized oil on growth performance, hematology and fillet quality of rainbow trout (Oncorhynchus mykiss)

Rainbow trout fish fed one of the diets containing fresh kilka oil with 50 mg kg-1 of vitamin E 1)without (control A, FO50) or 2)with hydrolyzed protein (4% replacement for fishmeal) (treatment B, FO50HP), 50 mg kg-1 vitamin E with oxidized oil 3)without (treatment C, OO50) or 4)with hydrolyzed protein (treatment D, OO50Hp), 250 mg kg-1 vitamin E with oxidized oil 5)without (treatment E, OO250) or 6)with hydrolyzed protein (treatment F, OO250HP) in a completely randomized design (six treatments and three replications) for eight weeks. The lowest FCR was in treatment B and the highest was in treatment E (P< 0.05). The amount of other growth indices were higher (P< 0.05) in treatments A and B than other treatments. The highest and lowest concentrations of alanin amino transferase (ALT) occurred respectively in treatment C and treatments A and B (P< 0.05), the highest and lowest concentrations of aspartate amino transferase (AST) occurred in treatments C and D and treatment B (P< 0.05), respectively. The highest neutrophil (Nut) and the lowest lymphosit (Lym) percentages were in treatment E while the vise versa were observed in treatment C (P< 0.05). The phagocytosis amount was highest in treatments C and D while it was the lowest in treatment A (P< 0.05). The fillet 14: 1n-9 concentration was the highest in treatment F while it was the lowest in treatment B (P< 0.05). The fillet 18: 0 content was the highest in treatment A and the lowest in treatment D (P< 0.05). Treatment D showed the highest fillet 20: 4n- 6 content while treatment F had the lowest content (P< 0.05). Accordingly, vitamin E (50 mg kg-1 diet) with hydrolyzed protein (as a substitute for fish meal by 4%) would be able to prohibit the damages resulting from oxidative stress in growing rainbow trout.