From waste to feed: Dietary utilisation of bacterial protein from fermentation of agricultural wastes in African catfish (Clarias gariepinus) production and health

A feeding trial was conducted to evaluate the effects of replacing fish meal (FM) with bacterial protein (BP) in African catfish (Clarias gariepinus) diets. Four iso-nitrogenous (369 g kg(-1)) and isolipidic (142 g kg(-1)) diets were formulated to replace graded levels (0%, 30%, 60% and 100%) of FM protein resulting in a dietary inclusion level of 0, 27.90, 55.70 and 93.00 g kg(-1) BP. Test diets were fed to the catfish (initial weight 18.17 +/- 0.25 g fish(-1), n = 20) in three replicate tanks. After 56 days of feeding, catfish fed with 30% BP diet had outperformed (P < 0.05) fish that were fed with the control diet (100% FM) in mean weight gain (MWG), percentage weight gain (PWG), specific growth rate (SGR) and metabolic growth rate (MGR). However, the growth response (MWG, PWG, SGR, and MGR) from diets containing 60% and 100% BP did not differ significantly to the dietary control. The whole-body protein (+8%) and lipid (+12%) contents of the catfish fed 30% BP diet were higher (P < 0.05) than no BP inclusion dietary group. The replacement of FM with BP in the catfish diets did not statistically affect the haematological status (P > 0.05), but not differ from 100% BP-fed diet (P 0.05). Indication of the liver health status was measured through serum aspartate transaminase, alanine transaminase, and alkaline phosphatase activities, and hepatocyte density, which remains statistically unchanged between the dietary groups (P > 0.05). Overall, the results show that BP can replace FM wholly or partly in African catfish (C. gariepinus) diet, without compromising growth performance, haemato-biochemistry, intestinal integrity, or liver functionality.

Automated summary

Replacing fish meal with bacterial protein in African catfish diets can improve growth performance and body composition without affecting hematological status or liver functionality.