Physical qualities of commercial extruded feed highly variable
Dr. Mette Sørensen, Norwegian University of Life Sciences, to discuss effect of raw ingredient formulations and extrusion processing parameters on nutritional and technical quality of aquafeeds at upcoming conference
Research carried out at AKVAFORSK and Aquaculture Protein Centre (APC) has shown that processing parameters such as extrusion temperature within a modest range (100-150oC) interferes slightly with nutrient digestion in rainbow trout. Physical quality of the feed, reported as durability index and hardness, was however reduced at the highest temperature.
Investigation of physical qualities of commercial extruded feed particles (i.e. particle hardness, durability, and water stability) has unveiled that quality is highly variable. Physical quality is affected by several variables among which formulation and extruder parameters are recognized as having great influence. Not only differences in chemical composition, but also pre-processing history of the raw ingredients affect physical quality of the feed, either directly or indirectly through interactions with extrusion parameters.
Significant differences were observed in technical quality of fish feed when fish meal was replaced with either toasted or untoasted soybean meal. Inclusion of soybean meal generally improved the technical quality in terms of hardness index and durability.
Resent research published by AKVAFORSK has indicated that there is a strong connection between pellet water stability and degradation pattern of feed particles in the gastrointestinal tract that moreover interferes with gastrointestinal transit rate and digestion in rainbow trout. Feed with low water stability caused separation and accumulation of dietary oil in the stomach of rainbow trout that may have resulted in oil belching and reduced lipid digestibility.
Results from investigations carried out by AKVAFORSK and Aquaculture Protein Centre into the effect of raw ingredient formulations and extrusion processing parameters on nutritional and technical quality of aquafeeds will be presented at Aquafeed Horizons.
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