Two assays were performed to evaluate the apparent digestibility of nutrients in horses diets, using the total collection of feces method and the markers chromic oxide, indigestible acid detergent fiber (iADF), indigestible neutral detergent fiber (iNDF), indigestible cellulose (iCEL), lignin (LIG), and insoluble acid detergent ashes (ADTA), as markers. In the first assay, five crossbred colts were used, fed five diets with different levels of crude protein, maintaining the relationship 50:50 concentrate to forage. The chromic oxide was used as external marker. In the second assay, four crossbred colts were fed diets composed by coastcross hay as forage and concentrate in the proportions of 40:60, 60:40, 80:20 and 100:00. In both assays, the cotents of indigestible acid detergent fiber, indigestible neutral detergent fiber, indigestible cellulose, lignin and acid detergent insoluble ash were obtained after in vitro incubation. In the first assay, the FDAi showed to be appropriate as internal marker to estimate the digestibility, and in both assays the CELi showed to be appropriate as internal marker for the estimate of apparent digestibility of nutrients of horses diets. The chromic oxide showed low fecal recovery in the first assay and the LIG showed low fecal recovery in both assays, underestimating the apparent digestibility coefficients of nutrients, and was inadequate to estimate the digestibility. ADIA, compared to the total collection of feces method, also showed to be inadequate to estimate the nutrient digestibility in equine.
digestibility; equines; markers; nutrients
