This study aimed to evaluate the nutrient composition and in vitro true digestibility of three rice straw (RS) varieties with varying stem lengths (Vasco (V): short-stemmed, Cammeo (C): medium-stemmed, and Efe (E): long-stemmed) treated with urea and/or crude glycerin. Each RS variety was ensiled in laboratory-scale mini-silos for 30 days using the following treatments: i) Control, ii) 5 % urea (U) treated RS, iii) 5 % crude glycerin (G) treated RS, and iv) 5% urea + 5% crude glycerin (UG) treatment RS. The Vasco variety of RS exhibited superior nutritional value compared to the Cameo and Efe varieties, with a greater (P<0.05) in vitro true digestibility of dry matter (IVTD_DM  (V:46.11%, C:41.17% and E:43.94%) as well as lower (P≤0.001) NDF (V:66.38%, C:71.68%, and E:68.59%) and ADF (V:43.61%, C:50.64%, and E:49.1%) levels. Silage of all cultivars demonstrated comparable responses to the applied treatments. The crude protein (P<0.001) and IVTD_DM (P<0.001) were greater in all treatment groups where urea was used alone or in combination with crude glycerin. All cultivars showed a reduction in NDF (P<0.001) and ADF (P<0.001) levels with the application of crude glycerin treatment alone, but no significant effect was observed on IVTD_DM values. In the interaction effect, Efe×UG showed higher (P<0.001) in vitro true digestibility while for in vitro NDF digestibility, Efe×U interaction exhibited higher (P<0.001) digestibility compared to other interaction effects. The findings of the study suggest that adding urea or a combination of urea and glycerin to rice straw improved its nutritional content and digestibility. Treating rice straw with a combination of urea (5%) and glycerin (5%) could be a promising strategy to improve its nutritional value for livestock feed.