Growth and protein utilization by juvenile catfish ( Clarias gariepinus) fed moist diets containing autolysed protein from stored lactic-acid-fermented fish-silage

Abstract

Fermented fish-silage was prepared from whole tilapias, 15% molasses and 5% Lactobacillus plantarum starter culture and used as protein supplement in moist diets for juvenile catfish, Clarias gariepinus. Carboxymethyl cellulose, guar gum or wheat gluten was incorporated as alternative binder into diets at 2% and their effects on water stability and nutrient leaching were determined. The pellets maintained a high water stability regardless of the binder used, and losses of total nitrogen were low (<8%) on a per gram diet recovered basis. Apparent digestibility coefficients for dry matter, nitrogen or lipid in the diets were high and similar when carboxymethyl cellulose or wheat gluten was used as the binder; but were reduced (P<0.05) with guar gum. C. gariepinus (mean weight, 18.5±1.3 g) were fed silage diets at 5% of body weight/day, twice daily, for 70 days in a recirculated water system with water temperature maintained at 27°C. Growth was better or similar when some of the protein was supplied by silage stored for 15 or 30 days, respectively. Differences in growth and protein utilization were demonstrated, but there were no effects on body (fillet) composition. The results showed that incorporation of autolysed protein in fish diets did not reduce dietary quality of feed for C. gariepinus. No morphological deformities were observed It is concluded that fermented silage stored for 15 days is beneficial as protein supplement in aquafeeds.