Post-Hatch Age Related Development of Spleen of Broiler Chicken: A Biometric and Histomorphometric View

Background and Objective: The primary organ of systemic immunity in birds is the spleen. In chickens, the spleen is the largest peripheral lymphoid organ, although little is known about how the spleen develops after hatching. Since the spleen plays a significant role in broiler chickens’ defensive mechanisms, the present study aimed to examine the age-related post-hatch development of the spleen, specifically its biometry and histomorphometry at various post-hatch developmental stages. Materials and Methods: The spleens of six different post-hatch developmental stages (post hatch day 1, day 7, day 14, day 21, day 28 and day 35) were taken after an ethical sacrifice (the cervical subluxation method) and subjected to biometric and histomorphometric evaluations. Biometric parameters (weight, length, width and thickness) were measured and for histomorphometrical study, selected formalin-fixed samples were processed and stained for microscopic analysis using a typical Mayer's Hematoxylin and Eosin stain. Results: The parenchyma of the spleen is formed of red pulp and white pulp that are intermingled with a lack of trabeculae and an identifiable marginal zone in all post-hatch age groups. A rising tendency in spleen capsule thickness, white pulp and lymphatic nodule length and breadth was noted. However, from day 14 onward, the white pulp size and the capsular thickness and from day 21 onward, the lymphatic nodules size were significantly (p<0.05) different among age groups. Conclusion: Although histologic structures were almost similar to other birds unlike mammals, values for the biometric and histomorphometric parameters were different from other bird species and even from indigenous and Sonali chicken.