Problem statement: Guar meal is a by-product consisting of hull and germ and is mostly used as a protein source in poultry and ruminant rations. The aim was to determine the effect of heat or heat-xylose processing on nitrogen fractions, in situ ruminal degradation parameters and in situ/in vitro ruminal and post-ruminal disappearance of guar meal. Approach: Samples were intact Guar Meal (GM), heat processed GM (GM hp , GM was heated at 100°C for 45 minute using industrial heater) and heat-xylose processed GM (GM hx , xylose was included in GM to give a final concentration of 10 g kg −1 DM, then was heat processed at 100°C for 45 minute using industrial heater N). Acid detergents insoluble nitrogen concentration of both GM and GMhp was significantly lower than that of GM hx (10.3, 11.29 and 18.53 g kg −1 nitrogen, respectively). In situ fractional degradation rate constant (c) of DM and CP was significantly decreased as a result of heat-xylose processing.Effective crude protein degradability of GM hp and GM hx was higher than that of GM. Post-ruminal disappearance of ruminal-undegradable CP of GM hx (0.965) was significantly higher compared with GM and GM hp (0.918 and 0.906, respectively). Conclusion: Results of the present study demonstrated that heat and heat-xylose processing might effectively protect the DM and CP of guar meal from ruminal degradation.