The accuracy, precision, and robustness of the cutin, acid detergent lignin (ADL), chromic oxide, and total feces collection to estimate the apparent digestibility of the organic matter of diets for equines were evaluated. For such, four male horses were used. They averaged 10 month-old and 197kg (170 to 216kg). The experiment was carried out in four periods with duration of eleven days each, being the first eight for adaptation to the diets and the three subsequent to obtain the results. The experimental design was a 4x4 latin square. The balance of the coefficients of digestibility of the organic matter for the markers was made by means of the bias. The accuracy and the precision were determined by the comparison of the predicted data with the observed ones, and the robustness by the comparison of the bias with other studied factors. The cutin did not show efficient as an internal marker, therefore it overestimated the apparent digestibility of the organic matter and showed to be less accurate and precise. The chromic oxide presented low fecal recovery and underestimated the apparent digestibility of the organic matter, even though it was more precise. The acid detergent lignin was the marker that got the best fecal recovery and was the most accurate, therefore, the most efficient marker.
horse; digestibility; markers; accuracy; precision
