The purpose of this research was to evaluate the partial replacement of soybean meal (SBM) for wet brewer's grains (WBG) or urea on the performance of lactating dairy cows. The second investigated whether WBG ensiled with corn kept animal performance in low- and high-producing dairy cows compared with WBG. In experiment I, 40 Holstein cows were used in 4 × 4 Latin square design. The treatments comprised WBG or urea as partial replacement for SBM, as follows: control (diet based on SBM and 1 % of urea), 10 % of WBG, 20 % of WBG, and 2 % of urea. Dry matter intake (DMI) was not affected by treatments. WBG increased milk yield linearly, but it decreased with urea. Milk fat content responded quadratically to WBG levels. Milk protein content decreased, while plasma urea nitrogen increased with high urea addition. In experiment II, 42 Holstein cows were divided into two groups according to production levels. Eighteen cows composed the group of low producing, while the high-producing group comprised 24 cows. The experimental design was a crossover with two periods of 14 days. The experimental treatments consisted of feeding WBG or WBG ensiled with ground corn. Regardless of the production level, no difference in milk yield and milk composition between treatments was observed.