Abstract:

The present study investigated the effects of the prebiotic inulin on the growth parameters, digestive enzyme activities and antioxidant status of rainbow trout (Oncorhynchus mykiss). After acclimation, fish (34±0.22 g; n = 135) were assigned into 9 tanks (15 fish per tank) and triplicate groups were fed a control diet (G-0) or diets containing 1% (G-1) or 2% (G-2) inulin. At the end of the trial (8 weeks), growth factors (final weight, weight gain, specific growth rate (SGR), food conversion ratio (FCR), protein efficiency ratio (PER), Economic conversion ratio (ECR), digestive enzyme activities (pepsin, trypsin, amylase and lipase) and antioxidant status superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) level of liver tissue were assessed. At the end of the study highest survival rate was observed in the fish fed with 1% G-1 inulin group. Similarly, digestive enzyme activities were significantly higher dietary G-1 group. Subsequently, elevated growth performance (final weight, SGR and FCR) was observed in trout fed with 1% compared to the control group. The effect of the dietary inulin on digestion was partly observed by assaying the activity of pepsin, intestinal amylase, trypsin and lipase. Apart from pepsin activity, results indicated that dietary supplementation of inulin is beneficial and may also have differential effects upon digestive enzyme activities. Antioxidant enzyme activity of SOD and CAT in liver tissue was generally higher in the supplemented inulin diets than in the control and significantly higher in the 1% inulin group. A significant decrease in MDA level of tissue was observed in all inulin supplemented groups when compared to the control group. These results indicate that inulin be considered as a beneficial dietary supplement for growth performance, digestive enzyme activities and antioxidant status of rainbow trout.

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