Submitted to: Aquaculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/12/2011
Publication Date: 4/21/2011
Citation: Morken, T., Kraugerud, O.F., Barrows, F., Sorensen, M., Storebaken, T., Overland, M. 2011. Sodium diformate and extrusion temperature affect nutrient digestibility and physical quality of diets with fish meal and barley protein concentrate for rainbow trout (Oncorhynchus mykiss). Aquaculture 317: Issues 1-4, Pages 138-145. Interpretive Summary: The method a feed is processed is essential for efficient production of farm raised fish. New ingredients such as barley protein concentrate are being develop to reduce dependence upon fish meal, and how processing affects these ingredients is an important question. This research demonstrated that temperature is an important factor during feed production and that sodium di-formate is an additive that will increase both the digestibility and quality (hardness) of the feed pellets.
Technical Abstract: The objectives of the experiment were to evaluate the effects of ingredient, extrusion temperature, and the acid salt sodium diformate (NaDF) in diets for rainbow trout on apparent nutrient digestibility and physical quality of the diets. The experiment was arranged in a 23 factorial design with two dietary ingredient sources (fish meal [FM] and barley protein concentrate [BPC]), two extruder temperatures (110 and 141 ºC), and two levels of NaDF supplementation (0 and 10.6 g kg–1). The results from the digestibility trial showed that addition of BPC increased the digestibility of crude protein (p<0.001) and several non-essential amino acids (NEAAs) (p<0.05), but reduced the digestibility of crude lipid (p<0.01), starch (p<0.01), and all essential amino acids (EAAs) (p<0.05). Extrusion at 141 ºC increased the digestibility of starch (p<0.001), crude protein (p<0.001), arginine (p<0.05), and several NEAAs (p<0.05), but decreased the digestibility of phenylalanine (p<0.01) compared to extrusion at 110 ºC. Addition of NaDF generally increased the digestibility of all major nutrients and individual amino acids (p<0.05). Diets with BPC had increased hardness (p<0.001), expansion ratio (p<0.01), and durability (p<0.001), but reduced the water stability (p<0.001) compared to the FM-diets. Extrusion temperature only affected pellet durability (p<0.01), which was highest for the highest temperature. Addition of NaDF to diets increased (p<0.001) the expansion ratio, durability, and water stability compared to diets without NaDF. In conclusion, this experiment showed that partially replacing FM with BPC negatively influenced the digestibility of several nutrients, but improved the physical quality of the diets. Diets extruded at the highest temperature had higher nutrient digestibility and durability. Inclusion of NaDF improved both the nutrient digestibility and physical quality of diets for trout, making it a value-adding additive.