Five total mixed rations (TMR) were formulated to evaluate the influence of partial total replacement of maize silage (MS) with Panicum maximum silage (PS) on digestibility, rumen fermentation and milk yield of cows. The experimental rations were TMR contained 100% Maize silage (MS, T1); TMR with 75% MS + 25% PS (T2); TMR with 50% MS + 50% PS (T 3); TMR with 25% MS + 75% PS (T 4) and TMR with 100% PS (R5).  Milk yield was performed on fifty Friesian cows (10 cows per treatment) for three months. Rumen fermentation and gas production were determined with Barki rams. The results cleared that CP content of both silages were close together, but ash and NDF were higher for PS but lactic and acetic acids were high for  MS. Gas production (GP) was lower for PS on both  24 and 48 h than MS. Meanwhile, both GP for soluble (a), insoluble (b) and the cumulative GP (y) were less with PS than MS, as well as DMD, OMD and SCFA. Rumen fermentation data showed higher NH₃-N, less TVFA^'s and acetic with the increase of PS in the rations, while the control, R2 and R3 had more acetic compared to other rations. Rations contained 25 and 50 % of PS had more milk and 4% FCM yields, while the lowest milk yield was obtained by incorporating 100% PS in ration (R5). It could be advisable to PS replacing MS in ration up to 50% without any adverse effect on milk production.