Age Related Observations on Gross and Microscopic Changes of Major Lymphatic Organs of Commercial Broiler Chicken

Abstract

The research was designed to study the age related changes of the gross anatomical and histological structures of lymphoid organs of broiler chicken of Bangladesh. The study was conducted in the Department of Anatomy and Histology, HSTU, Dinajpur. The broiler chickens of cobb-500 were grouped into six age groups D;, D7, D4, D2}, Dzg and D35. Each age group was consisting of five chickens. Chickens from each groups were killed with cervical subluxation and body weight of each chicken were recorded for the calculation of the relative weight of the lymphoid organs. For the gross study, various parameters including color, weight, length, diameter and number of the lymphoid organs were taken. Routine hematoxylin and eosin (H & E) stain was used to study the histology of the lymphoid organs. The thymus of the broiler chicken at the D, period the lobules were demarcated into cortex and medulla, which becomes larger and well demarcated at next period of life. In the study, Hassall's corpuscles were found during D, stage which increased in diameter and number at D3s5 stage of broiler chicken. The capsule and trabeculae becomes thicker with growth and development of the thymus. The single bursa of Fabricius was a dorso-median diverticulum of the proctodeum. Histologically, the bursa of D, stage was filled up by plicae and devoid of mucoid substances. The plicae contained few bursal follicles of different sizes. But with increasing age the bursa became larger with the plicae getting taller and thicker, which contained enormous number of large polyhedral primary and secondary lymphoid follicles. The spleen of broiler chicken was variable in size and shape but usually rounded. The color was reddish-brown to pinkish-brown at different period. From Dj; period, spleen was surrounded by connective tissue capsule which became gradually thicker with subsequent growth and development of the chicken. Splenic parenchyma became more distinct with increasing age. Cecal tonsils had four layers, which could be differentiated from D,. They became more prominent with the growth and development of the chicken. In D; the mucosa had few small folds which contains small amount of diffuse lymphatic tissues. But the folds subsequently became larger and broader with large amount of diffuse and nodular lymphoid tissues. Both primary and secondary lymphoid follicles were present from D; to D35. The lymphatic nodules were more in the mucosal layer of the cecum.