<em>Tenebrio molitor</em> and <em>Hermetia illucens</em> Larvae Meals in Juvenile Nile Tilapia Diets: Performance, Digestibility and Haematological Responses Under <em>Streptococcus agalactiae</em> Challenge

Insect meals are promising alternatives to conventional protein sources in aquafeeds, but comparative evidence in Nile tilapia (Oreochromis niloticus) remains limited. This study evaluated the effects of partially replacing an insect-free control diet with larvae meals from Tenebrio molitor and Hermetia illucens on growth performance, nutrient digestibility, haematological profile, and resistance to Streptococcus agalactiae in juvenile Nile tilapia. Fish were fed isonitrogenous and isoenergetic diets for 82 days: a control diet without insect meal and diets containing 100 g kg⁻¹ dry matter of T. molitor, H. illucens, or a 1:1 mixture. Growth performance and somatic indices were not affected by dietary treatment. Lipid digestibility remained high and similar among diets, whereas protein digestibility differed among diets and insect ingredients. Erythrocyte and total leukocyte counts were unchanged, but neutrophil and lymphocyte proportions differed among treatments. After intraperitoneal challenge with S. agalactiae, cumulative mortality was numerically lower in fish fed T. molitor or H. illucens than in the control group, although survival curves did not differ significantly. These findings indicate that both insect meals can be included at 10% in juvenile Nile tilapia diets without impairing growth, while influencing protein digestibility and leukocyte distribution.