Histomorphology of esophagus and intestine of Nile tilapia (Oreochromis niloticus) during the replacement of blood powder instead of fish meal in the diet

Tilapia is an omnivorous fish that uses different levels of food. This species is more of a filter feeder that provides its own food by refining the food in the environment. The aim of this study was to evaluate the histomorphology of esophagus and intestine under the influence of replacing blood powder with fish powder in the diet of Nile tilapia. After preparation, fish were fed with designed diets containing 0, 25, 50, 75, and 100% blood powder for 8 weeks and each treatment was performed with three replications. After this period, the fish were anesthetized and after opening the abdominal area 0.5 cm tissue samples were taken from the esophagus and intestine, fixed in 10% formalin buffer, and after tissue preparation steps included dehydration with alcohol, clarification with xylol, blocking with paraffin, cutting 4-6 microns thick with microtome were done. Hematoxylin-eosin staining were performed and the study of microscopic slides were performed under a light microscope. The results of measuring and measuring indices such as height and thickness of villi, the thickness of epithelium and muscle layer, and change in the number of mucous cells in the esophagus and intestine in the group receiving blood powder completely and 75% compared to the control group and other groups has been less. Therefore, blood powder in the diet is somewhat tolerable and replaceable for the species.