In this study, nutrient composition and use of silage after harvest of waste green parts (herbage) of tomato (Licopersicon esculentum L.) were researched as a wet forage source for ruminants. Three different silages of tomato herbage: without additive (TS), with 5% sugar beet molasses (TSm), or 5% crushed barley grain (TSb) were prepared. The forage quality and the in vitro ruminal digestibility, gas production, organic acids, and some estimated digestion parameters for different silages of tomato herbage were determined. Besides, the in vitro digestion values of using at 25%, 50%, 75%, and 100% rates instead of corn silage in the dairy cattle total mix ration (TMR) were researched. The lactic acid content of TSb silage was higher than those of the TS and TSm silages (P < 0.001). The ensiling of tomato herbage with barley decreased the levels of acetic, butyric, and propionic acids in the silage (P < 0.01). The use limits of tomato herbage silages instead of corn silage in dairy cattle TMR were determined as 25% for TS, 75% for TSb, and 100% for TSm in terms of in vitro gas production and other digestion parameters during 24-h incubation. The volume of methane produced for mL/g DM at 24 h was decreased by increasing TS in dairy cattle TMR (P < 0.001) but was not changed by increasing TSm and TSb in dairy cattle TMR (P > 0.05). Consequently, results have shown that tomato herbage should be ensiled with 5% molasses. However, it has been concluded that using tomato herbage silage with barley up to 75% or sugar beet molasses up to 100% instead of corn silage in dairy cattle ration did not have a negative effect in vitro.