Pattern of fecal endogenous nitrogen excretion in rats fed leguminous diets.

The main objective of this investigation was to establish the pattern in relation to time of the rat fecal endogenous nitrogen excretion by continuous feeding of balanced diets containing common peas, cowpeas or common beans as the protein sources (10% protein), labeled with 1.000 atoms % of 15N-excess. Nitrogen of endogenous origin was measured by the isotope dilution method in a 6-day experiment. Fecal excretion of endogenous nitrogen of rats fed the leguminous diets was roughly twice that of rats fed the non-protein diet (88 mg, 42 mg), and the excretion of total fecal nitrogen did not differ among leguminous diets. From the third to the sixth day of the experiment, the endogenous nitrogen excretion, either as a percentage of quantity (mg), attained a statistically non different value (p > 0.05). A common pattern of excretion of fecal endogenous nitrogen as a function of time was expressed by a strong negative (r < -0.95) power regression (y = A.x-B) for the common pea, the cowpea or the common bean diets. Conversely, the excretion of dietary nitrogen did not show a common pattern as a function of time for all experimental diets.

The use of nitrogen-15 labeling for the assessment of leguminous protein digestibility.

This study evaluated the digestibility of leguminous protein labeled with 15N, by using nitrogen balance and quantitation of fecal endogenous nitrogen (FEN), determined by isotopic dilution, in order to correct apparent values. Seeds of common beans, cowpea and common pea labeled with 1.000 atoms% of 15N-excess were used as protein sources in diets for 60 male Wistar rats, during a 6-day assay. The real digestibility values obtained with FEN were 77.6, 84.4, and 86.3% for common beans, cowpea and common pea, respectively. They were higher and statistically different (p < 0.05) than true digestibility values, corrected by non-protein diet. FEN showed a direct, moderate and positive relation with weight of dry matter eaten, initial body weight, weight gain and weight of dry matter of feces, the latter showing the highest correlation, with a coefficient r = 0.8930 at 1% level.