Growth and histomorphological responses of <i>Chindongo socolofi</i> to the long‐term replacement of fish meal with defatted <i>Tenebrio molitor</i> meal

Abstract The long‐term suitability of defatted Tenebrio molitor larvae meal (TM) as a substitute for fish meal (FM) protein was evaluated in Chindongo socolofi over a 170‐day feeding period. Six isonitrogenous (38% crude protein) and isoenergetic (4396 kcal kg −1 ) diets were formulated, in which TM protein replaced FM protein at 0% (control), 20%, 40%, 60%, 80%, and 100%. A total of 180 fish (initial weight 0.44 ± 0.01 g; length 3.14 ± 0.08 cm) were randomly distributed into six treatments in triplicate and fed to apparent satiation twice daily. Growth performance was assessed at an intermediate time point (day 88) and at the end of the trial (day 170) to monitor temporal changes in treatment responses. During the first 88 days, no significant differences in growth performance were detected among fish fed the control, 20%, 40%, and 60% TM diets ( p &gt; 0.05). However, prolonged feeding revealed that inclusion levels exceeding 20% resulted in reduced growth performance. Histological analyses, including semi‐quantitative scoring of hepatic lipid accumulation and morphometric assessment of intestinal villi, demonstrated dose‐dependent alterations in liver and intestinal tissues in groups receiving higher TM inclusion. In contrast, survival rate was not significantly affected by dietary treatments. These findings suggest that defatted TM can replace up to 20% of the FM protein in diets for C. socolofi without impairing growth or tissue integrity under long‐term feeding conditions. Higher substitution levels, although tolerated in the short term, may compromise physiological conditions when applied over extended periods.