The effects of dietary nucleotide type (Hilyses and Augic15 ) on growth performance and salinity resistance of kutum, Rutilus kutum (Kamensky, 1901) fingerlings

Abstract

The aim of this research was to evaluate the effects of dietary nucleotides on performance, immune system and salinity resistance of kutum fingerlingsduring migration to the sea. Five experimental diets were prepared by addition of Hilyses (0.75 and 1.5%) and/or Augic¹⁵ (0.3 and 0.6%) to a control diet. After eight weeks adding nucleotide diets, fish were exposed to saline water for 48h. Supplementation of both nucleotide sources improved fish growth parameters (<em>p</em><0.05). Fish mortality was also decreased by the additives in both fresh and sea water. Glucose and cortisol levels significantly decreased with the administration of both nucleotide sources (62 to 69 versus 75 mg dL^-1 for glucose and 6 to 8.5 versus 9.8 mg dL^-1 for cortisol (<em>p</em><0.05). Supplementation of Hilyses and /or Augic¹⁵ increased lysozyme activity in the blood (<em>p</em><0.05) and maximum activity has observed in fish fed at high doses of Hilyses and Augic¹⁵diets. In conclusion, an improved performance of <em>R. kutum</em> fingerlings fed on or with both nucleotide sources may suggest that kutum fingerlings require a larger dietary nucleotide at early life stage to control stress related parameters such as cortisol and glucose.