Dietary replacement of fish meal with Antarctic krill meal improves growth, immune response, and disease resistance in Litopenaeus vannamei

Feed formulation plays a critical role in determining the quality, cost-effectiveness, and sustainability of aquaculture production. Fish meal (FM), the traditional primary protein source in shrimp feed, has become increasingly expensive due to global supply limitations. Antarctic krill meal (KM), derived from Euphausia superba , represents a nutritionally balanced and potentially sustainable alternative. This study evaluated the effects of replacing FM with KM in the diet of Pacific white shrimp ( Litopenaeus vannamei ). Five isonitrogenous and isolipidic diets were formulated with graded levels of FM replacement: 0 % (F1), 25 % (F2), 50 % (F3), 75 % (F4), and 100 % (F5), corresponding to KM inclusion rates of 0 %, 6.6 %, 13.1 %, 19.7 %, and 26.3 %, respectively. Shrimp were fed for 30 days, and growth performance, immune responses, and disease resistance were evaluated. Shrimp fed F4 and F5 diets showed significantly higher final body weights (13.14 ± 0.6 g, p = 0.03; and 14.00 ± 0.1 g, p < 0.001, respectively) than the control (F1 = 10.82 ± 0.3 g), along with improved feed conversion ratios ( p < 0.01). Immune assays revealed elevated total and granular hemocyte counts, phenoloxidase, and phagocytic activity, particularly in F3–F5 groups. Post-challenge tests indicated that diets with 25–75 % KM replacement delayed mortality following White Spot Syndrome Virus (WSSV) infection and reduced Enterocytozoon hepatopenaei (EHP) loads. Among treatments, the F4 diet (75 % FM replacement) demonstrated near-optimal growth, immune enhancement, and pathogen resistance, suggesting it as the most effective and commercially viable formulation. These results confirm that krill meal offers both nutritional and immunological benefits as a fish meal substitute in shrimp aquaculture. While krill meal offers clear nutritional benefits, its long-term sustainability depends on strategic use at functional levels and integration with novel, eco-efficient feed ingredients to reduce environmental impact and support scalable, responsible aquafeed production. • Growth and immunomodulatory effects of krill meal supplement in shrimp feed were studied in Litopenaeus vannamei. • Immune parameters of L. vannamei were positively upregulated by the optimal dietary krill meal levels. • L. vannamei cultured with feeds containing varying ratios of krill meal replacements show potential to enhance tolerant against both microsporidian (EHP) and viral (WSSV) infections.