Growth and protein utilization by juvenile catfish ( Clarias gariepinus) fed dry diets containing co-dried lactic-acid-fermented fish-silage and protein feedstuffs

Abstract

Fish-silage (FS), prepared from lactic acid fermentation of whole tilapias, 5% sugar beet molasses and 2% Lactobacillus plantarum, was blended and co-dried with soybean meal (SBM), poultry by-product meal (PBM), hydrolysed feather meal (HFM) and meat and bone meal (MBM). The blends were evaluated as protein source (providing 50% of dietary protein) in dry diets (40% protein, 4·3 kcal g −1 gross energy) for juvenile catfish, Clarias gariepinus, fed at 4% body weight day −1 for 70 days. The fish-silage pellets maintained their shape during water immersion and their water stability was high and similar ( P>0·05) to that of a reference diet. Clarias gariepinus fed on the different fish-silage diets showed some significant ( P<0·05) differences in mean weight gain, specific growth rate and protein productive value, but feed conversion and protein efficiency ratios were similar ( P>0·05). Protein digestibility was reduced ( P<0·05) in catfish fed diets containing FS: HFM while digestibility of energy content was lower ( P<0·05) in those fed diets containing FS:SBM and these low values were responsible for the poor performance of catfish in both treatments. There were no effects among treatments on carcass composition, hepatosomatic index, histology of pancreas, liver and intestine tissues, or on haematocrit and haemoglobin contents. Fermented fish-silage codried with protein feedstuffs is a suitable protein supplement, which can provide up to 50% of dietary protein without affecting feed efficiency, fish growth or health.