The high moisture sorghum grain silage is an important source of feed for livestock in Uruguay and some regions of the world. That is why this study aimed to evaluate the effect of ensilage time, moisture content, and variety on the in vitro fermentation ruminal parameters of moist sorghum grain stored in experimental silos. This study was conducted to analyze gas production in vitro of two sorghum grains varieties, with high and low-tannin content, ensiled with15–25%, 26–32%, and 33–42% moisture content 30, 90, and 180 d of ensilage in experimental silos. Total gas production was higher in low-tannin grains than in those with high-tannin, regardless of the ensilage time or the moisture content. Differences in the gas production rate were also observed in the interactions between tannin and moisture content, ensilage time, and moisture content as between tannin content and moisture contents for the lag time. Moreover, medium moisture content promoted the fermentability in hightannin grains and high moisture in low-tannin grains. The fermentability of both high and low-tannin grains was enhanced with increasing ensilage time.