치어기 넙치(Paralichthys olivaceus)의 소화 생리에 저어분 사료가 미치는 영향

Abstract

The quality feed source significantly affects the digestive activity of fish and thus directly impacts its growth and development. The main protein source in fish feed is fishmeal, which causes great environmental pollution, so the use of fishmeal should be reduced, Therefore, in this study, the development of digestive tissue and intestinal hormone and digestive enzyme activity was confirmed to analyze the digestive activity of the juvenile olive flounder (Paralichthys olivaceus) fed a low-fishmeal diet. Fish averaging 7.86 ± 1.26 g in weight were fed four experimental diets; the experiment contained 70% fishmeal content was used as a control (FM70, CON), 45% of fishmeal replacement from CON (FM45), 35% of fishmeal replacement from CON (FM35A), 35% of fishmeal replacement from CON adding 7% insect meal, and 1% insect oil replacement (FM35B). The water temperature was recorded ranging from 16.8 to 18.1℃. During the feeding experiment, 20 fish were randomly collected from each tank at two-month intervals, and the growth performance was measured. Besides, liver, stomach, pyloric caeca, and intestine were sampled to evaluate the digestive physiology. The hematoxylin and eosin stains were used for the digestive organs by the method of organizational analysis. The alcian blue and periodic acid-Schiff’s solution were used for intestine and pyloric caeca organs by the method of histochemical properties analysis. The immunohistochemistry was applied for the pyloric caeca and liver to analyze the expression of the digestive hormone cholecystokinin (CCK), and pancreatic polypeptide (PP). The ELISA was applied to the intestine to analyze the expression of digestive enzyme trypsin, chymotrypsin, and lipase. The experimental result showed no difference in growth performance among the experimental groups (p>0.05). As a result of confirming the juvenile digestive organ tissue, the development of pepsin cells of the stomach, the mucosal folds of the anterior intestine and, hepatocytes was increased in all the experimental groups. In the intestine and pyloric caeca, the distribution of goblet cells was no difference between the control (FM70) and the experimental groups. The CCK and PP expression did not significantly differ among any of the experimental groups. Trypsin, chymotrypsin, and lipase activities in the intestine also have no significant difference. These results suggest that a diet comprising 35% fishmeal with added insects will not affect the digestive physiology of P. olivaceus in commercial fish farming in Korea.