Nutritional and antinutritional aspects of an Argentinian soy flour assessed on weanling rats

Inactivation of antinutritional factors on an Argentinian deffated soy flour was evaluated in relation to its corresponding original soybeans. Residual urease and trypsin inhibitors activities, protein solubility, available lysine and phytic acid showed acceptable levels. The nutritional value of a diet based on the same soy flour was compared with that of a casein-based diet by allowing them to each one of two groups of weanling IIMBeta rats during 28 days. Non-significant differences were obtained between groups comparing both body weight gain per gram of protein intake as well as the results of histometric studies performed on the small intestine. Thus, this soy flour contained appropriately inactivated antinutritional factors and its protein content and quality were nutritionally suitable. Large intestine hypertrophy was revealed within the soy-fed group suggesting increased microbial proliferation attributable to non-digestible oligosaccharides and fiber-like compounds. These compounds, employed by gut microflora as fermentation substrates, would be also responsible for an increased nitrogen excretion in the soy-fed group in relation to controls. This increment of nitrogen excretion significantly lowered the value of apparent nitrogen digestibility in the soy-fed group in relation to the casein-fed control one. Nevertheless, nitrogen apparent digestibility in the soy-fed group was equal or higher than other values reported from distinct treated soy meal-based diets.