Metabolic fecal nitrogen and digestibility estimates in the grasscutter (Thryonomys swinderianus)

The metabolic fecal nitrogen and digestibility estimates in the grasscutter were determined using 12 captive-bred adult animals fed with four experimental diets differing primarily in crude protein content using nitrogen balance trial approach. Grasscutters required 343.5 mg N kg^-0.75 d^-1 of nitrogen to meet maintenance requirements, which were met on diets containing 7.4% crude protein. The true digestibility of nitrogen was moderate (52%) but within the range for eutherians. Dry matter intake increased with decreasing dietary nitrogen content, suggesting that animals on nitrogen-deficient diets displayed appreciable compensatory intake. Metabolic fecal nitrogen was 3.5 g N kg^-1 dry matter intake, and endogenous urinary nitrogen was 257.5 mg N kg^-0.75 d^-1. The low value of metabolic fecal nitrogen found for grasscutters affected the dry matter intake required for nitrogen balance, and it may allow grasscutters to exploit nitrogen poor diets.