Serum Biochemical Changes and Acute Stress Response s of the Endangered Iridescent Catfish ( Pangasianodon hypophthalmus ) Supplied with Dietary Nucleotide

Abstract

The effects of dietary nucleotide (NT) were evaluat ed on some serum biochemical parameters and acute stress responses of the catfish ( Pangasianodon hypophthalmus ). Five experimental diets including 0, 0.25, 0.5, 0.7 5, and 1% NT were supplied to catfish fry for 10 weeks. At the end of the experiment, fis h fed the control and 1% NT diets were subjected to handling and crowding stress. The resu lts showed that the fish supplied with 0.25-0.75% NT had a lower level of lactate dehydrogenase (LDH ) (P<0.05) while other serum enzymes including alkaline phosphatase (ALP), asparate transaminase (ASP), and alanine transaminase (ALT) were not significantly r educed by NT inclusion in the diet (P>0.05). The fish which received the highest doses (0.75 and 1% ) of NT exhibited higher levels of triglyceride than the other groups (P<0.0 5) while they showed no significant differences in other biochemical parameters includi ng total protein, albumin, globulin, cholesterol, and glucose (P>0.05). To investigate s tress responses, cortisol (primary response), serum glucose, and serum ion concentrati ons including sodium, potassium and calcium (secondary responses) were measured. The re sults showed significant fluctuations in all the tested components during the sampling in tervals for up to 48 h post-stress; the exceptions, however, were glucose in the group on t he 1% NT diet as well as serum cortisol and calcium levels in those supplied with the control diet. Based on the results obtained, it may be concluded that dietary NT can i mprove liver function in iridescent catfish, but it has no obvious positive effects on other serum biochemical parameters and stress responses. Keywords : Crowding stress, Cortisol , Handling stress, Liver function.