Mineral Composition of Rumen Fistula Samples Compared to Diet

Abstract

Forage sampling using fistulated grazing animals is a generally accepted technique to measure dietary forage quality and botanical composition, but is it a satisfactory technique to evaluate dietary mineral intake? Using a variety of diets which were fed to rumen-fistulated steers, the fistula samples had relatively larger concentrations of ash, Si, Na, P, Zn, and Co (P<0.05) than did diet samples. Small decreases in the Mg and Ca concentrations of the fistula sample, as well as the small increases in N, K, Mn, Fe, and Mo values, were not generally different from diet concentrations. Regression equations predicting diet-mineral concentrations of all diets, given the concentration in the fistula sample, were accompanied by errors of 8 to 37% of the true value. Smaller errors can be expected when similar diets like alfalfa hay are used throughout a given study.