Effects of dietary supplementation of Pleurotus pulmonarius stalk meal on growth, gut microflora and intestinal morphology of Clarias gariepinus were assessed in this study. The stalk meal was incorporated at 0.0 g/100 g (Control), 2.5 g/100 g (PSM 2), 5.0 g/100 g (PSM 3), 7.5 g/100 g (PSM 4) and 10.0 g/100 g (PSM 5). Clarias gariepinus (n=375), with an initial weight of 10.84±0.04 g, were allotted at 25 fish/60 litres of water in a completely randomised design for each diet treatment in triplicate. Feeding trial was conducted for eight weeks. Weight gain, specific growth rate, survival rate, feed intake and feed conversion ratio were not significantly different across all diet treatments. However, the production performance index of the fish and protein efficiency ratio were higher in fish fed PSM 3 diet than other treatments. Total viable bacteria count in the gut ranged from 7.56 (PSM 2) to 8.34 log10 cfu/g (PSM 4), while lactic acid bacteria count was between 5.00 (control) and 7.03 log10 cfu/g (PSM 3). Escherichia coli were identified in the gut of the control group but were not detected in those fed supplemented diets. More colonies of Salmonella and Vibrio species were observed in the control but fewer colonies in the diets supplemented groups. The proximal, middle and distal villus length, proximal, middle and distal cryptal depth, proximal and distal absorption area of fish fed supplemented diet were higher than those of the control. Conversely, proximal, middle and distal villus width and middle absorption area were not significantly different. In spite of observable favourable gut microflora and gut histomorphology of fish fed supplemental P. pulmonarius stalk meal diet, these attributes did not manifest in growth performance indices.
