Nutrients and toxicants in rapeseed meal: a review

The composition of rapeseed meal and hulls is reviewed with emphasis on components of nutritional interest. Carbohydrates in rapeseed meal are mainly pectins, pentosans and cellulose and comprise nearly one-half the gross energy. The digestibility of energy is lower for rapeseed than for soybean meal. Protein is well digested, but the protein digestion coefficient and the availability of amino acids are lower than for soybean meal. Data on digestible and metabolizable energy are summarized. The kinds of glucosinolates present in high (HG) and low (LG) glucosinolate rapeseed meal and the nature of their hydrolytic products are discussed. The toxic effects of oxazolidinethione , isothiocyanates, thiocyanates and nitriles, and their relationship to their parent glucosinolates , to myrosinase action and to conditions during rapeseed processing are reviewed briefly. The effects of glucosinolates in animal tissues and products and the effects of converting to LG rapeseed meal are presented. Finally, a brief review is given of the responses of swine and cattle to the feeding of HG and LG rapeseed meal. The nutritional advantages of LG rapeseed meal, over the older type HG meal, are clearly evident from the feeding trials.