Influence of dietary nucleotides on growth performance and stress resistance in Kutum (Rutilus kutum Kamenskii, 1901)

A feeding trial has been conducted to evaluate the effects of dietary nucleotide (NT) on growth performance and stress resistance of fry kutum (Rutilus kutum Kamenskii, 1901). A basal diet supplemented with 0 (control), 0.3, 0.5 and 0.7 g NT kg-1 have been formulated for four experimental diets. After 8 weeks of feeding trial, growth parameters were evaluated and then fish has exposed to osmotic stress. To elucidate the underlying physiological mechanisms, cortisol, apoptosis and HSP70 levels were measured at selected times of 0, 2 h, 8 h and 24 h after the osmotic shock. The results revealed dietary NT feed exerts a positive effect on the growth performance of kutum fries and fish fed with 0.7 g  NT kg-1 had the highest final weight compared with other treatments (p<0.05). Results of HSP70 showed that fish fed with NT had higher levels of HSP70 expression. Also, the levels of HSP70 at 2 h increased significantly, 3-7-fold over baseline levels (0 h) and then decreased significantly at 24 h, however HSP70 levels at 24 h was 1-3-fold over baseline levels. Apoptosis and cortisol values were affected by dietary NT levels and all NT groups showed lower stress-induced apoptosis and cortisol elevation, compared to control group.