Age features of the microscopic structure of the intestines of the budgerigar (Melopsittacus undulatus)

Information about the morphology of the budgerigar intestines is a necessary condition for the preparation of diets for feeding, prevention and treatment of diseases of the digestive system, the state of which determines the intensity of growth and development of the bird’s body. The features of the histological structure of the intestines of the budgerigar (Melopsittacus undulatus) of 9 ages: 1, 3, 7, 14, 21, 30, 60, 180 and 365 days of age were studied. Histological preparations were made according to the classical method with hematoxylin and eosin staining of sections, according to Mallory and Grimelius. Morphometric parameters of microstructures were determined on preparations from a transverse section of the middle section of the duodenum, jejunum, ileum and rectum. In the intestinal wall of the budgerigar, three membranes were identified: mucous, muscular and serous. Three layers were found in the mucosa: epithelial, lamina propria, and muscular lamina. The predominant type of epitheliocytes were rim enterocytes, goblet cells were found in a smaller number, the number of which increased towards the rectum, as well as enteroendocrine cells, which were located mainly in the crypts. The muscularis mucosa consists of several layers of cells of smooth muscle tissue, which delimits the lamina propria from the muscle membrane, encircles the crypts, and accompanies the blood capillaries of the villi. The submucosa was not found. The muscular coat consists of two layers formed by smooth muscle tissue: the inner circular and the outer longitudinal. The enteric nervous system is represented by two nerve plexuses: the submucosal, located between the muscularis mucosa, and the myenteric, located in the outer layer of the muscular membrane. There was a general pattern of increase in changes in most parameters with age : the diameter of the intestine, wall thickness, mucous membrane and muscle membrane, height, width and surface area of the villi, the depth of the crypts. Changes in the size of the microstructures of the intestines were asynchronous. The most intensive changes in the size of microstructures occurred in the first month after hatching, especially in the first week. They corresponded to the values of an adult bird mainly at 21–30 days of age. A decrease in the thickness of the wall, mucosa, height of the villi, and their surface area in the direction from the duodenum to the rectum was established.