This study investigated the effects of silage supplementation of grazing dairy cows. Forage mixtures used in the four week trial with rumen fistulated cows in five treatments enabled rumen sampling to determine effects of diet on rumen parameters. Five groups of ten cows were grazed on a restricted daily allowance of 18 kg dry matter (DM) pasture/cow, and four groups received sulla silage (S) or maize silage (M) alone or in mixtures to make up 40% of total intake. A sixth group was given an unrestricted (38 kg DM/cow.day) pasture allowance. Samples of rumen liquor data demonstrated significant effects of supplement.