This study aimed to determine the nutrient content and rumen fermentation product in-vitro of rice straw from rice of the IR variety fertilized using organic and inorganic fertilization. This research used experimental methods. This study examined two paddy fields located in Datar Village, Sumbang District, Banyumas. Land A used inorganic fertilizer (urea and phonska) and Land B used organic fertilizer from cattle dung. Both of those lands were planted with IR variety rice. Samples were 20 points on each land obtained by random sampling so that all parts of the field were represented. All samples were dried in the oven at 600C. Variables measured were nutrient contents such as crude protein (CP), crude fiber (CF) and rumen fermentation product in-vitro of volatile fatty acids (VFA) and ammonia nitrogen (N-NH3 ). Statistical analysis used t-test. Result showed that CP and CF contents and rumen fermentation products of VFA of rice straw from organic fertilizer were higher (P0.05) in the rumen fermentation product of N-NH3 between organic and inorganic fertilizer. It can be concluded that rice straw quality from IR variety rice can be improved through organic fertilization. Keywords: organic, fertilizer, rumen, nutrient, rice straw