Evaluation of internal markers in digestibility estimation for sheep and goats.

The objective of this study was to compare the indirect methods of obtaining digestibility with the direct method of total fecal collection to estimate the apparent digestibility of nutrients in sheep and goats supplemented with non-protein nitrogen. Five goats and five sheep with no defined racial pattern were used, distributed in two 5 × 5 Latin squares, with split plots, considering the diets as plots and the apparent digestibility determination methodologies as subplots. The diets were composed of buffelgrass hay and the addition, via ruminal infusion, of increasing amounts of nitrogen supplementation in order to gradually raise the CP level of the basal diet in intervals of 2% points, that is, + 2, +4, + 6 and + 8%. Samples of the feeds offered, and the leftovers were collected daily during the five days of collection to determine the nutrient intake, as well as the total collection of feces to determine the apparent digestibility of the nutrients. The amount of fecal dry matter excreted was estimated by the concentration of Indigestible Acid Detergent Fiber (ADFi), Indigestible Neutral Detergent Fiber (NDFi), Indigestible Dry Matter at 244 h (DMi 244 h) and Indigestible Dry Matter at 264 h (DMi 264 h). Among the evaluated markers, DMi 264 h had the lowest accuracy in estimating fecal excretion and nutrient digestibility. For the goat species, the markers ADFi and DMi 244 h proved to be able to adequately predict fecal excretion and digestibility indices, while NDFi stood out for both species. Among the evaluated markers, NDFi is the one that most accurately estimates the nutrient digestibility of the diet for goats and sheep.