Diet Processing and Soybean Products for Mink

The effects of moist extrusion processing of diets containing fish meal and defatted soybean meal or untoasted defatted soybean flakes on amino acid composition, trypsin inhibitor activity and apparent digestibilities of nutrients were studied. Three diets were formulated: one based on fish meal as the protein source and the other two diets forty percent of the total amino acids were substituted with either soybean meal or white flakes. Each diet was fed to mink as an unextruded mixture or as extruded pellets to determine the effect of extrusion. Extrusion processing did not change the amino acid composition of the diets, but reduced the trypsin inhibitor activity by approximately 76 percent. Diet intake, digestibility of crude protein, amino acids, and fat were lower, but starch higher, in the unextruded white flake diets compared to the fish meal and soybean meal diets. No significant differences were found between the extruded diets. Extrusion of the white flake diet increased digestibility of protein and amino acids. It was concluded that the heat involved in extrusion was sufficient to inactivate the trypsin inhibitor activity and to increase the protein digestibility in the unheated white flake treatment to approximately the same level as found in soybean meal and fish meal diets.

Romarheim, O.H. and co-workers. 2005. Effect of extrusion on trypsin inhibitor and nutrient digestibility of diets based on fish meal, soybean meal and white flakes. Archives Animal Nutr. 59(6): 365-375.