Effect of fiber in sorghum on nitrogen digestibility

Digestibility measurements were carried out on a population of 12 Cameroonians whose habitual diet, deficient in animal products, is based on consumption of sorghum meal which supplies between 2.4 and 4.2 g of crude fiber per 100 g of dry matter. Over an 11-day period, the 12 subjects received successive diets of 3.3, 4.8, and 5.4 g of crude fiber per 100 g of dry matter. The increase in fiber intake resulted in a significant rise in quantity of fecal matter excreted, including nitrogen and formic insoluble substances. On the other hand, the highest urinary nitrogen losses were obtained from the diet least rich in fiber. The apparent digestibility of nitrogen dropped from 65.4 to 60.5% and then further to 56.9%. The apparent digestibility of nitrogen of the diet least rich in fiber differed significantly from those of the other two diets. The subjects under study did not benefit from an adaptive physiology which would enable them to reduce digestive nitrogen losses. Intestinal disappearance of crude fiber augmented significantly and then stabilized when switching from the diet least rich in fiber to the two others, i.e., from 15.1 to 19.9 g/day and then 19.8 g/day. This population was distinguished by its ability to breakdown large quantities of fiber and to reduce urinary nitrogen loss when fecal nitrogen output rises. Apparent nitrogen balances remained positive.