Supplementary effects of dietary vitamins C and E on resistance against the stress of stocking density in rainbow trout (Oncorhynchus mykiss)

Document Type : Research Paper

Authors

1 Department of Fisheries, Faculty of Marine and Atmospheric Sciences and Technologies, Hormozgan University, Bandar Abbas, Hormozgan, Iran

2 Fisheries Department, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Guilan, Iran

Abstract

Effects of vitamins C and E - supplemented diet on hematological indices of rainbow trout Oncorhynchus mykiss juveniles at two different densities were investigated in a 6-week trial. Rainbow trout juveniles (initial body weight of 9.6 ± 0. 69 g) at two stocking densities of 50 and 100 fish per 50 liters were fed three diets containing the same level of protein and fat, but with different levels of the vitamins. Experimental diets included diet 1 without vitamins, diet 2 supplemented with 1500 mg/kg vitamin C and diet 3 with 600 mg/kg vitamin E. A total number of 1350 rainbow trout  juveniles were devided in six treatments each with three replicates as T50(0) (density = 50, fed diet 1), T100(0) (density = 100, fed diet 1), T50(C) (density =  50, diet 2), T100(C) (density = 100, diet 2), T50(E) (density = 100, diet 3) and T100(E) (density = 100 diet 3). After a 6-week feeding, hemoglobin level, the number of red blood cells and sodium level were significantly higher in T100 treatments (P<0.05). Plasma glucose and cortisol were also significantly higher in T100 treatments (the highest in T100(0)) than in T50 treatments (the highest in T50(0)) (P<0.05). T50 treatments had higher levels of blood albumin and total protein (P<0.05). There were no significant differences in number of white blood cells and potassium level between treatments (P>0.05). According to the results, supplementing the diet of rainbow trout with vitamins C and E enhances fish resistance to the stressful environment caused by stocking density.

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