Global fish culture has grown in leaps and bounds in the past three decades with projections revealing potentials for further growth provided the different bottlenecks bedevilling the industry, such as quality, locally available , environmentally-friendly and cost-effective feed and feed ingredients, are addressed (Hua et al., 2019) . Many solutions have been suggested to tackle these challenges but on a general note, investigators agree that re-use of waste stream or by-product , after its valorization, could be a pragmatic and sustainable approach (Tham et al., 2023; Verreth et al., 2023 ). Meat and bone meal (MBM) is a byproduct from a slaughter processing plant and it has previously been suggested as a promising substitute to fish meal (FM) in aquafeed because of its high protein and digestibility (Moutinho et al., 2017; Lee et al., 2023) . Against this background, we investigated the suitability of MBM as an alternative to FM in diets for Clarias gariepinus juveniles.
Four isonitrogenous (40% crude protein) and iso-energetic (18.42 kJ/g) diets were formulated. The control diet contained 33% FM with no MBM (MBM0) and three other diets in which MBM progressively r eplaced FM at 11 (MBM11), 22 (MBM22) and 33% (MBM 33). The diets were fed to triplicate groups of C. gariepinus juveniles (16.21±0.05 g) and their growth, carcass composition, tissue histology and intestinal morphometry were assessed after a 60-day feeding period. The least weight gain (77.61 g/fish ) and specific growth rate (3.11 %/day) were observed in the group fed diet MBM33 and these values were significantly (P<0.05) lower than the group that received diets MBM0 and MBM11 (Table 1) . Similar trend was observed in the diet utilization parameters expressed as feed conversion and protein efficiency ratio . The cost of production (USD/kg) in the group that received MBM33 and MBM22 were significantly (P<0.05) higher relative to those of MBM0 and MBM11 fed groups. Histology of the intestine showed that the villi across dietary groups were well differentiated; however, they were significantly (P<0.05) reduced in length in the MBM33 fed group . Villi width, crypt depth and survival were unaffected (P>0.05) by dietary treatment. The study revealed that only 33% (110 g/kg) of FM protein can be substituted by MBM without impairing growth, feed and economic efficiency of C. gariepinus juveniles.