serum biochemical changes and acute stress responses of the endangered iridescent catfish (pangasianodon hypophthalmus) supplied with dietary nucleotide

the effects of dietary nucleotide (nt) were evaluated on some serum biochemical parameters and acute stress responses of the catfish (pangasianodon hypophthalmus). five experimental diets including 0, 0.25, 0.5, 0.75, and 1% nt were supplied to catfish fry for 10 weeks. at the end of the experiment, fish fed the control and 1% nt diets were subjected to handling and crowding stress. the results showed that the fish supplied with 0.25-0.75% nt had a lower level of lactate dehydrogenase (ldh) (p0.05). the fish which received the highest doses (0.75 and 1%) of nt exhibited higher levels of triglyceride than the other groups (p0.05). to investigate stress responses, cortisol (primary response), serum glucose, and serum ion concentrations including sodium, potassium and calcium (secondary responses) were measured. the results showed significant fluctuations in all the tested components during the sampling intervals for up to 48 h post-stress; the exceptions, however, were glucose in the group on the 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 improve liver function in iridescent catfish, but it has no obvious positive effects on other serum biochemical parameters and stress responses.