The effect of glutamine on digestive enzymes and intestinal structure of Siberian sturgeon (Acipenser baeri, Brandt 1869)

The Siberian sturgeon is a suitable species for using in aquaculture industry. The purpose of this study was to investigate the effect of glutamine on intestinal digestive enzymes and histological structure of intestine in Siberian sturgeon and to determine the optimal amount of glutamine in rearing conditions. This study was performed on 126 fish with a mean weight of 45.71 ± 7.56 g in six treatments (control, 5, 10, 15, 20 and 30 g glutamine /kg feed) and three replicates during 8 weeks in Shahid Dr. Beheshti Sturgeon Restoration and Genetic Conservation Center in Sangar, Rasht. Fish intestine was prepared for study the digestive enzymes activity and Arabic gum-olive oil emulsion, azocasein 2.5% and starch were used as substrate to measure lipase, protease and amylase enzymes, respectively. For examination of villus length and intestinal epithelium, 1 cm of intestinal tissue was fixed in Bouin's solution. The samples were then dehydrated, clarified, paraffin-embedded and molded. After sectioning tissue, staining was performed by eosin-hematoxylin method. The results showed that amylase, protease and lipase were significantly different between treatments (p<0.05). The highest amount of amylase and lipase levels was observed in treatment of 30 g glutamine and the highest amount of protease was in treatment of 20 g glutamine. Also, the size of intestinal villi length and intestinal epithelium were significantly different among treatments (p<0.05). The highest intestinal villi length was observed in treatment of 20 g glutamine and the highest intestinal epithelium was seen in treatment of 30 g glutamine. Because of the highest secretion of amylase, protease and lipase enzymes and the highest villus length and intestinal epithelium in treatments of 20 and 30 g glutamine, these levels could have a positive effect on the structure of intestinal physiology and the digestive enzymes in this fish.