A SURVEY OF NUTRIENTS AND TOXIC FACTORS IN COMMERCIAL RAPESEED MEAL IN CHINA AND EVALUATION OF DETOXIFICATION BY WATER EXTRACTION

Information is presented concerning the utilization of Chinese rapeseed by-products as animal feed. Results were obtained from more than 200 samples from various oil mills. For screw-pressed cake and prepress-solvent extracted meal, respectively, crude protein averaged 389 and 432 g kg-1 on a dry matter basis; residual lipids 106.and 19 g kg-1; crude fibre 132 and 138 g kg-1; ash 87 and 99 g kg-1; calcium 8 and 9 g kg-1; phosphorus 11 and 12 g kg-1; lysine 3.7 and 3.4 g per 16 g N. The meal was found to contain 1.5 +/- 1.1 mg g-1 oxazolidinethione and 1.4 +/- 1.0 mg g-1 isothiocyanates; whereas the cake contained 2.3 +/- 2.2 and 2.7 +/- 1.8 mg g-1, respectively. Approximately 5-6 g kg-1 tannins and 20 g kg-1 phytates were determined. Detoxification involving water extraction alongside seed processing was examined on a pilot scale, and the meal was evaluated in feeding trials with pigs, broilers and rabbits. Water extraction removed nearly all glucosinolates and significantly increased crude protein content. Remarkable improvement in animal growth performance was achieved when feeding detoxified meal compared with untreated feed. The treatment rendered the meal suitable for use as a main protein supplement as proved by feeding trials.