Nutritional study of two Brazilian soybean (Glycine max) cultivars differing in the contents of antinutritional and toxic proteins

The research was conducted with two different recently released Brazilian s oybean cultivars (Rio Balsas and Bays) to evaluate whether there is any cor relation between the different levels of antinutritional and/or toxic prote ins in the cultivars and their nutritive value as sources of protein for mo nogastric animals (rats). Furthermore, it is discussed, for the first time, the role of the dietary soyatoxin on the performance of rats fed on diets containing soyatoxin-rich (cv. Bays) and soyatoxin-free (cv. Rio Balsas) so ybean cultivars. Feeding rats with diets containing raw soybean cultivars s howed a lower growth rate, net protein utilization and digestibility, a muc h higher dry matter and nitrogen excretion and macroscopic alterations in i nternal organs when compared to rats fed on egg-white protein. The nutritio nal parameters measured fur the diet based on raw Bays cultivar were poorer than those of the diet prepared with Rio Balsas. In the raw soybeans, tryp sin inhibitor and lectin, and urease to a lesser extent, significantly affe cted at different fashion the soybean protein utilization. Heating treatmen t of the Bays seeds increased the growth rate, NPU, in vivo protein digesti bility and practically eliminated or attenuated all the organ alterations o bserved. This study might be helpful in the choice of safe and nutritious s oybean cultivars. (C) 2001 Elsevier Science Inc. All rights reserved.