Skipjack Tuna (Katsuwonus pelamis) Liver-Derived Feed Additive Potently Enhances Bursa of Fabricius Follicular Development in Broiler Chickens

Abstract

This study was driven by the potential of skipjack tuna liver—a nutrient-rich byproduct containing 51.67% protein and essential amino acids—as a functional feed supplement. Rather than focusing solely on growth performance, I directed my attention to the bursa of Fabricius, the primary lymphoid organ in birds responsible for B lymphocyte maturation. Histological changes in this organ serve as a sensitive indicator of humoral immune system activity. A total of 300 day-old Cobb 500 broiler chicks were divided into four treatment groups over a 17-day period: a control group receiving basal feed, and three experimental groups supplemented with 1%, 3%, and 5% skipjack tuna liver powder per kg of feed. On day 18, the bursae were collected, processed using standard hematoxylin-eosin staining, and subjected to morphometric analysis. Follicle, medulla, and cortex areas were measured using ImageJ software. The quantitative results were striking. In the control group, the mean follicular area was 29,617.67 µm². The 5% supplementation group exhibited an approximately threefold expansion, reaching 87,206.28 µm². The medullary area—the site of B cell proliferation—increased significantly from 11,827.26 µm² in controls to 25,488.56 µm² in the 5% group. Similarly, the cortical area expanded from 17,792.41 µm² to 61,717.72 µm². These significant expansions across all follicular compartments provide quantitative evidence that skipjack tuna liver powder supplementation actively stimulates the development of this primary lymphoid organ. These findings demonstrate that this byproduct functions not merely as a nutritional source, but as a bioactive immunomodulator capable of strengthening the foundation of the adaptive immune system in broiler chickens during their critical early growth phase.