The study was conducted to determine the effect of acid (HCl) treatment on ruminal degradation characteristics of dry matter (DM), crude protein (CP), and effective degradability of groundnut cake (GNC). GNC was either soaked in or sprayed with 0.5N HCl .The treated cake was either air or oven dried at (100ºc). Nylon bags technique was employed using three castrated calves. HCl treatment significantly (P < 0.05) decreased in situ dry matter degradation rate. GNC air dried represented the lowest P<0.05 CP degradation at all incubation periods except at time interval 36hrs. GNC sprayed had the highest CP degradability at all the incubation periods. Combining heat with HCl was the most effective treatment in protecting GNC from rumen degradation, while spraying resulted in the least protection.