Macro- and microstructure of the oesophageal tonsil in turkeys during the post-vaccination period

The successful development of poultry farming depends on the state of the immune system of birds, which from the first days of life come into contact with a significant amount of antigens that enter the body mainly through the digestive tract and provoke the development of diseases. Food retention in the transition zone between the oesophagus and stomach leads to the development of the oesophageal tonsil, as one of the most developed immune formations. The purpose of this study was to find out the development of the oesophageal tonsil in turkeys and determine the timing of its full morphofunctional maturity by vaccine prevention. Material for macro- and microscopic studies was selected from 66 individuals of Big-6 turkeys in the early stages of the postnatal period of ontogenesis, which were divided into experimental and control groups. When performing the study, classic morphological research methods were used. It was shown that in both groups of turkeys, the levels of structural organisation of the lymphoid tissue that forms the base of the oesophageal tonsil arise in a certain sequence, but with different intensity. In day-old birds, the first level was revealed – diffuse lymphoid tissue, represented by local clusters of diffusely located lymphocytes, some of which migrate into the surface epithelium and have close contact with epithelial cells. On day 10, the experimental group of turkeys developed pre-nodes with dense arrangement of lymphocytes without a capsule (second level) and primary lymphoid nodules with pre-nodes were recorded at 10 days of age, and primary and secondary lymphoid nodules at 20 days of age. This may indicate that on day 20, the oesophageal tonsil, as an immune formation, acquires morphofunctional maturity, and its cells are able to recognise and destroy specific antigens. The results obtained contribute to elucidating the natural mechanisms of development of immunological processes in poultry in ontogenesis, which should be considered by veterinarians when developing new vaccine prevention strategies