Insights on Feed Characteristics of Tuna Moist Extruded Aquafeeds Using Glycerol

Extruded aquafeeds have been used to replace natural food supplies. As tuna aquaculture still relies on fish stocks, the development of formulated extruded diets is essential to guarantee its responsible intensification. Accordingly, three extrusion trials were done aiming to optimize the extrusion process in extruded tuna diets, namely, a pre-trial with varying levels of dietary lipid (6, 8, or 10%), trial 1 with varying die temperature (40, 80 and 100°C), and trial 2 with varying dietary glycerol content (0, 4, and 8%). Rich-lipid diets were successfully manufactured through a single-screw extruder, and additional lipid content could be added through coating. Die temperature between 40°C to 100°C significantly (P<0.05) influenced the feed characteristics (e.g. moisture content decreased with increasing die temperature), except penetration. Finally, the addition of glycerol significantly (P<0.05) increased moisture content and penetration of moist extruded feeds. It is concluded that a supply around 0.5–1.0% of glycerol might be valuable towards the development of moist diets. However, further research on the effects of glycerol addition in the diet on digestibility and performance of fish need to be continued for developing moist extruded diets.