In vitro and in vivo nutrient digestibility in sheep of rations with and without residue from the extraction of tamarind pulp Digestibilidade in vitro e in vivo de nutrientes em ovinos para rações

This study evaluated the digestibility of nutrients by, and parameters associated with, in vitro fermentation using different inocula (sheep ruminal fluid and feces) as well as the in vivo digestibility in sheep that were fed rations with 50% concentrate containing either no (0%) residue from the extraction of tamarind pulp (RETP) or 15% RETP. To determine the in vitro digestibility (IVD) of nutrients, two sheep, weighing 40.38 ± 2.10 kg, were used as inoculum donors. To determine the in vivo digestibility of nutrients, we used four sheep and a 3×2 factorial experimental design, with three methods of digestion of nutrients and two experimental rations (0% and 15% RETP). The variables were subjected to analysis of variance and the variables that showed differences at 5% probability were further analyzed using the Tukey test at 5% significance. The IVD using different inocula did not significantly differ (p>0.05) from the in vivo digestibility in sheep for dry matter (DM), organic matter (OM), and neutral detergent fiber (NDF). The different methods for determining nutrient digestibility did not affect (p>0.05) the digestibility of DM, OM, crude protein (CP), NDF, and acid detergent fiber (ADF) in rations with 0% and 15% RETP. However, the IVD of CP for rations containing 0% and 15% RETP incubated with both inocula was lower (p<0.05) than the CP digestibility in vivo. The in vivo digestibility of ADF for rations containing 0% and 15% RETP was higher (P<0.05) than the IVD using sheep ruminal fluid and feces as inocula. The pH values and concentration of ammonia nitrogen (NH3-N) after in vitro incubation for 24 h and the in vivo assay were not different (p>0.05) for the rations containing 0% and 15% RETP, but the pH and NH3-N of both fermented and rumen contents differed (p<0.05) depending on the inocula used and the in vivo assay. In summary, the digestibility of DM, OM, and NDF can be determined by the in vitro fermentation method using the ruminal fluid or feces of sheep as inocula in rations containing 0% or 15% RETP. However, in vitro fermentation is not a suitable method for the determination of pH and NH3-N concentration.