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

Simon Davies and colleagues in Nigeria led by Dr Ayodeji Adeoye are moving the sustainable agenda forward to utilising Single Cell Protein Microbial biomass from bioconversion of organic vegetable waste! Literally from waste to feed for fish! In this case the African catfish (Clarias gariepinus) very popular in Nigeria and S Africa! It’s a healthy and lean fish!

This collaborative effort also involved Dr Alex Wan and his team at NUIG (National University of Ireland in Galway) and Simon! A truly international network of fish nutrition research!

We are very pleased with the outcome in the recent paper as it will all help to validate alternate proteins for fish to reduce our fish meal and soya dependence in future bespoke feed formulations! It is important for socio-economic improvement and securing a transparent food chain!

Bacterial protein produced from fermentation of agricultural wastes can be utilised as a relatively cheap ingredients of low environmental footprint in the manufacture of aquafeed•

Bacterial protein can partly or wholly replace fish meal in the diet of African catfish without adverse effect on the fish overall growth performance, haemato-biochemical status, intestinal morphology and hepatic function•

Dietary replacement of fish meal by bacterial protein (at 30%) enhances the growth performance of African catfish•

Bacterial protein improves the nutritive value of the African catfish whole-body composition.

Abstract

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−1n = 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). While histological analysis of the catfish mid-intestine showed intact epithelial barriers with extensive mucosal folds extending into the lumen. The intestinal perimeter ratio of fish fed with 30% BP diet was higher (+32%) than those of the dietary control group (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.

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