Physical and nutritional properties of moist fermented fish silage pellets as a protein supplement for tilapia (Oreochromis niloticus)

Fish silage was prepared by fermentation of stunted tilapia with 50 ml/kg Lactobacillus plantarum starter culture and 150 g/kg sugar beet molasses at 30°C for 7 days, pasteurized, neutralized, and stored at 30°C for 180 days. Addition of 50 ml/kg onion extract proved effective as lipid antioxidant, with peroxide values lower than the control (P<0.05). The wet silage was mixed (2:1, w:w) with poultry by-product meal, soybean-hydrolysed feather meal blend or menhaden fish meal; and each mixture pelleted by cold extrusion method. The moist pellets maintained a firm consistency during water immersion for 10 min and pellet stability was similar (P>0.05) among diets. Protein and lipid losses were low (<15%) on a per gram diet recovered basis. All-male Oreochromis niloticus fingerlings (mean weight, 56.2±3.7 g) were fed each pellet at 4% of body weight/day for 15 days in a recirculated system (temperature, 27°C; flow, 3 l/min). Apparent digestibility coefficient (ADC) for dry matter, crude protein and gross energy of the pellets were high (>80%) and similar (P>0.05) among diets. Moist fish silage pellets were physically stable and highly digestible to O. niloticus, and suitable as farm-made feeds for fish.