NOVEL DIETARY STRATEGY FOR OVERCOMING THE ANTINUTRITIONAL EFFECTS OF SOYBEAN WHEY OF HIGH AGGLUTININ CONTENT

A diet-switching experiment, which aimed to improve the utilization of soyabean whey was carried out for 61 d with young rats, Feeding was a rranged in such a way that after a few days on the soyabean diet, the rats were switched to a high-quality lactalbumin diet for a short peri od, after which the cycle was repeated several times. The weights of t he rats at the end of the soyabean phases were significantly less than those of animals pair-fed on a high-quality diet throughout, However, the test group regained the weight loss after switching to the lactal bumin diet. After three cycles there were no significant differences b etween the weights of the test rats fed on a poor soyabean diet for ov er a third of the experiment and those fed on the lactalbumin diet thr oughout. Feed conversion was always significantly higher with test rat s in the lactalbumin period than with continually pair-fed controls. S imilarly, faecal N losses were significantly higher for test rats in t he soyabean phase, but these differences disappeared after switching t o the lactalbumin diet. At the end of the experiment there were no sig nificant differences in body protein or lipids between the groups alth ough the pancreas was significantly heavier while the liver was lighte r in soyabean-fed rats. The high destruction of trypsin inhibitors in the gut suggests that they probably had little effect on protein diges tion in the gut. In contrast, as selective depletion of the agglutinin from soyabean whey removed the nutritional benefit in the lactalbumin part of the cycle, the improved feed conversion in this period must h ave been the result mainly of the survival and functionality of soyabe an agglutinin and the benefits due to the hyperplastic growth and fast er renewal of the gut surface it induced. As processing is unnecessary , this novel method is cheap and can be easily adapted for the use of soyabean whey, regarded as a waste product.