Three feeding experiments, each with 24 cows, were performed to evaluate the use of effluent from grass silage as feed. The quality of silages produced in open‐drainage silos and closed‐drainage silos was also compared. Silage and effluent were fedad libitumwith concentrate supplements. Animals readily consumed effluent at 30 kg day−1on average, equivalent to 2.2 kg dry matter (DM) day−1. Silage intakes decreased by 1 kg DM day−1when silage plus effluent was fed as compared with silage alone, while total roughage intake (silage plus effluent) increased by 1.2 kg DM day−1. Milk yields and fat, protein, and lactose contents tended to increase for cows receiving effluent. Increases in milk yield were small, however, relative to the increases in DM intake, indicating reduced feed conversion efficiency when effluent was fed. Intakes of silage stored in the presence of effluent tended to be lower than those of silage from which effluent had been drained, but milk yield and milk composition were unaffected.