Detoxification of rapeseed meal by extrusion with an added basic salt

A commercial, high-glucosinolate, rapeseed meal with no added salt or mixed with 2, 5, or 10% NH4HCO3 was extruded under different processing conditions using the Wenger TX-52 twin-screw extruder. Male Wistar rats were fed 13 diets containing 15% rapeseed meals (including nonextruded) or a casein-based control diet. After six weeks, blood samples were taken, and serum was analyzed for thyroid hormones. Extrusion processing under all salt and steam conditions tested reduced glucosino-late levels in the meal, but no significant correlation was found between intensity of the treatment conditions and glucosinolate reduction. Higher weight gains, feed efficiencies, and thyroid hormone profiles were observed with use of the extruded meals; but no treatment completely detoxified the meal. Histopathological evaluation showed that thyroid and other tissue abnormalities occurred in all animals except those fed the casein diet. Antinutrients, including glucosinolates and probably volatile nitriles, in the meal were reduced by extrusion processing under the basic conditions of this experiment.