Search

Abstract: This study was conducted to investigate the effects of dietary red seaweed, Gracilaria pygmaea level on growth, antioxidant‐related parameters, digestive enzyme activity and intestinal morphology of rainbow trout (Oncorhynchus mykiss) fry. Five isocaloric and isonitrogenous diets were formulated to contain four G. pygmaea levels (30 (GL‐30), 60 (GL‐60), 90 (GL‐90) and 120 g/kg (GL‐120)), and a control diet was used, without inclusion of seaweed. Results of the feeding trial indicated that final body (FBW: 2.8–3.5 g) and specific growth rate (SGR: 4.8–5.2) were significantly improved when 60 g/kg G. pygmaea was supplemented in the diets. However, there was a significant reduction (p < .05) of final body weight (FBW) and specific growth rate (SGR) in fish fed 120 g/kg G. pygmaea. Protease activity was significantly lower in fish fed GL‐120 diet when compared to GL‐30 or control (p < .05). Lipase was significantly affected by dietary seaweed regardless its level of supplementation (p < .05). The inclusion of the Gracilaria in the diet led to evident changes in the fish antioxidant status with significant reduction of superoxide dismutase, glutathione peroxidase activity and lipid peroxidation products. The histological study demonstrated that all groups of fish displayed normal morphology of anterior intestine and pyloric caeca. Villi absorptive area in the anterior intestine of treatment groups GL‐90 and GL‐120 significantly decreased (p < .05). Overall, the results obtained in this study indicate that dietary G. pygmaea supplementation up to 90 g/kg improves growth performance in rainbow trout fry without compromising antioxidant responses and digestive function. [ABSTRACT FROM AUTHOR]

The effects of dietary n-3 highly unsaturated fatty acids [eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)] with α-tocopherol on growth, non-specific immune response and oxidative status were investigated in Caspian brown trout, Salmo trutta caspius, fry. Six experimental diets containing three different dietary levels of n-3 HUFAs (low: 1 + 0.5% of total fatty acids, DHA+ EPA, medium: 2 + 1%, DHA + EPA, high: 4 + 2%, DHA + EPA) with two different levels of α-tocopherol (low: 300 and high: 1000 mg kg−1 diet) were prepared and named: LL, LH, ML, MH, HL and HH (HUFA/α-tocopherol) groups, respectively. Diets were fed to triplicate groups of 60 fry with an initial weight of 600 ± 25 mg for 10 weeks. Results showed that increase in dietary DHA and EPA up to high level improved fry growth in terms of the body weight and specific growth rate, particularly when dietary α-tocopherol levels were high, suggesting a higher antioxidant protection value when these fatty acids are high. At all dietary n-3 HUFA levels, increase in α-tocopherol from low to high level enhanced the alternative complement (ACH50) activity. Fry fed diets medium and high n-3 HUFA displaying significantly higher lysozyme activity ( P < 0.05). Moreover, fish fed medium or high levels of n-3 HUFA had significantly lower prostaglandin E2 (PGE2) than those fed low n-3 HUFA ( P < 0.05). Significant differences in antioxidant enzymes (catalase, glutathione peroxidase, glutathione S-transferase, glutathione reductase and superoxide dismutase) activity were also observed between groups, with higher activity in high levels of n-3 HUFA ( P < 0.05). Results of this study suggest that the effect of dietary n-3 HUFA on examined non-specific immunity parameters are not uniform; however, these impacts are closely related to the α-tocopherol supplement and their interaction. In conclusion, increased dietary levels of n-3 HUFA and α-tocopherol would enhance growth performance and welfare of this species. [ABSTRACT FROM AUTHOR]