Precision of Indirect Methods for Estimating Digestibility of Forage Consumed by Grazing Cattle

Abstract

Comparisons were made of the lignin ratio and the fecal nitrogen index methods of estimating digestibility of diets of grazing animals. Special attention was given to sources of error and variability in these estimates. Evaluation of indirect methods of estimating digestibility of grazed forage were made by sampling forage from the range with esophageally-fistulated steers and later feeding it to sheep in conventional digestion trials. Regression equations for predicting diet digestibility from fecal nitrogen and factors for correcting for lignin digestibility were obtained from the digestion trials with sheep. These equations and correction factors were used with composition data for fecal and forage samples from steers on the range to calculate digestibility under grazing conditions.