This research was conducted to investigate the effects of two dietary emulsifiers on nutrient digestibility and lipase activity in rainbow trout (Onchorhyncus mykiss). A basal rainbow trout diet containing fat powder supplemented with 10 and 5 g kg −1 of cholic acid, and 20 and 40 g kg −1 of Tween-80. Control diet contained no emulsifiers with fat powder was replaced by fish oil. Each diet was randomly assigned to 1,500-L tanks in triplicate. Juvenile rainbow trout with an initial weight of 27.32 ± 2.03 g were randomly distributed in the experimental tanks. The results showed that growth parameters did not change by the addition of the two emulsifiers (p > .05). Total triglyceride content was significantly higher in control fish fed diet containing fish oil (p < .05), while serum cholesterol content showed no significant differences among treatments (p > .05). Control diet resulted in a higher fat digestibility than those of other experimental diets. However, protein and ash digestibilities in diet containing emulsifier were higher than those of the control diet. Control group showed the lowest lipase activity, whereas 20 g kg −1 Tween-80 diet caused the highest lipase activity among treatments (p < .05). In conclusion, it seems that a higher lipase activity induced by the emulsifiers could not compensate for the negative impacts of fat powder on the experimental diets. K E Y W O R D Semulsifier, enzyme activity, fat digestibility, fat powder, lipase, rainbow trout

Global fish oil production is expected to be unsustainable because of distinction of ocean stocks and high demand (Natale et al., 2013).These limitations have forced aquaculture industry to replace lipid sources (Oliva-Teles et al., 2015). Among the fat sources, fish oil has been an ideal option to be added in fish diet in case of having unsaturated fatty acids and higher digestibility. On the contrary, using terrestrially based lipids like vegetable oil and fat powder, as alternative fat sources, could decrease the requirement for fish oil but they may reduce lipid digestibility (Amirkolaie et al., 2014). Vegetable oils are more resistant to lipolysis process than fish oil since lipase prefers to use polyunsaturated fatty acids as substrate (Austreng et al., 1979). On the other hand, low cholesterol level of vegetable oils

Our study was concentrated on the effect of garlic peel on haematological parameters, biochemistry and digestive enzymes on beluga juvenile (Huso huso) with mean body weight of 18. 41 ± 0. 89 g after the feeding trial for 90 days. Garlic peel powder added with 0%, %0.5, %1, %1.5 and %2 of feed to basic sturgeon diet (49% protein and 14% lipid). ultimately, haematological parameters, biochemistry, digestive enzyme activity were evaluated. Results showed that the hemoglobin (Hb) was remarkably greater in the treatment fed garlic peel diet in comparison with the control (p<0.05), while others blood indices did not significant differences (p>0.05) between juveniles fed control and garlic peel supplementation diets. The group fed 1.5% garlic peel showed highly significant different in total protein (p<0.05).