Chemical and nutritional quality of dried fermented fish silages and their nutritive value for tilapia ( Oreochromis niloticus)

Abstract

Fish silage was prepared from whole juvenile tilapia by fermentation with 50 g kg −1 (wet weight, w/w) Lactobacillus plantarum at 30°C using 150 g kg −1 (w/w) molasses, corn flour or tapioca flour as alternative fermentation (carbohydrate) substrates. After incubation for 7 days, a desirable and stable pH of less than 4.5 was attained and the source of fermentation substrate did not affect the soluble nitrogen content or the proximate composition of the liquid silage after 30 days storage. Soyabean meal, used as filler material, was blended with the liquid silage in ratios 1:1, 2:1, 3:1, 3:2 (w/w) and oven-dried. The various proportions of fish silage:soya-bean meal improved the dry matter (DM) and nutrient composition of the silage after drying. The 1:1 dried fish silage was incorporated into dry pelleted diets (650 g kg −1 diet) formulated for tilapia ( Oreochromis niloticus). The pellets had a tough consistency and maintained their shape during water immersion. Water stability of dried fish silage pellets were similar ( P>0.05) to that of a reference diet. Apparent digestibility coefficients for DM, protein and energy of the silage diet were 82.8%, 84.5% and 82.8%, respectively. It was concluded that co-dried fermented fish silage is suitable and has a potential as a protein feedstuff in fish diets.