Ensiling tropical grasses presents a challenge in achieving an optimal fermentation profile, particularly when the grass possesses high nutritional value. Therefore, this study aimed to evaluate the use of additives during ensiling as a strategy to enhance the fermentation profile and nutritional quality of Zuri grass (Megathyrsus maximus cv. BRS Zuri) silage harvested at two regrowth ages. The tested additives were: control (CT); Lactiplantibacillus pentosus strain AV 14.17 (LP); cellulase (CE); and LPCE (LP + CE). The regrowth ages were 60 and 90 days. Increased regrowth age of zuri grass resulted in a higher fermentability coefficient but a reduced crude protein content in the fresh forage. The CE and LPCE silages exhibited lower fibre content. The crude protein content was higher and the ammonia content was lower in the CE and LPCE silages when the grass was harvested at 60 days. The pH was lower in CE and LPCE silages at both regrowth ages. Butyric acid was detected only in the CT and LP silages when the grass was harvested at 60 days. The CE and LPCE silages showed greater effective digestibility. The indigestible fraction of neutral detergent fibre was higher in silage harvested at 90 days. The addition of cellulase, alone or combined with the L. pentosus strain, effectively solubilized the fibre components, resulting in a lower pH and more effective control of undesirable microorganisms, thus improving the nutritional value. The most significant results were obtained when zuri grass was harvested at 60 days of regrowth.