In some areas of the world irrigation is needed to grow alfalfa and the use of crop residues and feed coproducts in dairy rations may represent opportunities to reduce the dairy industry’s use of water. A study using indirect calorimetry and 12 multiparous lactating Jersey cows (BW = 447.5 ± 43.7 kg; DIM = 71 ± 11 d, mean ± SD) was conducted to determine the effect of feeding a mixture of straw and distillers dried grains with solubles (DDGS) in replacement of alfalfa hay on milk production and energy utilization. A replicated 4 × 4 Latin square design was used to evaluate the replacement of alfalfa hay with a coproduct mixture (CoP) containing approximately 1/3 wheat straw and 2/3 DDGS. The experimental treatments were as follows (proportions on a DM basis): a control diet (CON) containing 18.2% of alfalfa hay, a low coproduct diet (LCP) that contained 8.1% of CoP, a medium coproduct diet (MCP) that contained 16.3% of CoP, and a high coproduct diet (HCP) that contained 24.3% of CoP. No differences (P ≥ 0.307) were observed for dry matter intake, milk, and protein yield averaging (mean ± SEM) 19.5 kg ± 0.60, 29.6 kg ± 0.91, and 1.05 kg ± 0.04, respectively. Increasing the proportion of CoP tended to result in a quadratic (P = 0.06; SEM = 1.06) effect in energy corrected milk which increased from 37.6 to 39.0 in CON and MCP but then decreased to 36.6 in HCP. Increasing the proportion of CoP linearly (0% to 24% total DM) decreased free water intake (P = 0.02; 17.2% reduction) and methane production (P < 0.01; 19.7% reduction). The concentration of gross energy in the diet increased (P < 0.01) linearly with the inclusion of CoP with the concentration of digestible energy (P = 0.09) and metabolizable energy tending to increase (P = 0.07) linearly with the inclusion of CoP. The concentration of net energy balance was not observed to be affected by treatment. Results of this study indicate that alfalfa hay with a mixture of straw and DDGS can maintain milk production and dry matter intake but the replacement with the CoP mixture may result in some differences in energy utilization mostly driven by effects on methane production.