RAPESEED DOCKAGE. EFFECTS OF FEEDING RAW AND PROCESSED WILD MUSTARD AND STINKWEED SEED ON GROWTH AND FEED UTILIZATION OF MICE

Abstract

Wild mustard seed (Brassica kaber), stinkweed (Thlaspi arvense) and rapeseed (B. napus 'Tower') were fed in diets for growing mice as ground raw seed and as cooked, petroleum ether-extracted meals. In exp. 1, wild mustard seed at 0, 2 or 4% and stinkweed seed at 0, 1 or 2% were substituted for part of the rapeseed in a 3 × 3 factorial design. The control diet contained 20% rapeseed and casein was used to equalize protein levels at 16%. Growth and feed utilization were not affected (P > 0.05). The failure of diets (exp. 1) with 14 – 20% rapeseed and up to 6% weed seeds and containing active myrosinase to depress growth more markedly, is attributed to the relatively low total glucosinolate levels in the diets. In exp. 2, the meals from wild mustard, stinkweed and rapeseed were compared with soybean meal in diets in which each meal provided 3, 6 or 9% protein, with casein used to bring dietary protein to 16%, in a 3 × 4 factorial design. Weed seed meals resulted in lower feed intakes (P < 0.05), with wild mustard meal being the lowest. Increasing levels of wild mustard seed meal and stinkweed seed meal reduced growth rates (P < 0.05), but it is concluded that such meals as contaminants of normally processed commercial rapeseed meal can be fed at relatively high levels in myrosinase-free diets without risk associated with glucosinolates. Key words: Rapeseed dockage, mustard, stinkweed, growth, mice