A study using 4 multiparous Holstein dairy cows, which were 93.5 ± 22.2 DIM, was conducted to determine the effect of conventional and corn milling co-products, specifically dried distillers grains and solubles (DDGS), on milk production, composition, and methane production. A 4 × 4 Latin square was utilized and included 4 treatments, namely a zero control (C) and diets that contained 30% of the diet DM as either conventional DDGS (ConDG), or 15% reduced fat DDGS (RFDG) or a mixture (Mix) of 15% conventional DDGS and 15% reduced fat DDGS. In all 3 treatment diets, DDGS were included in replace of corn and soybean meal. Cows were housed and fed in individual stalls and fed once per day and milked twice per day for 4–28 d periods. During the last 2 d methane production was measuring using indirect calorimeters. Cows consuming DDGS consumed more (P = 0.05) feed (22.7, 24.8, 26.4 and 27.3 ± 1.57 for the C, RFDG, Mix and ConDG respectively). Likely in response feed intake, milk yield was also increased (P < 0.01) by feeding DDGS (29.4, 39.4, 38.2, and 38.0 ± 3.22 for the C, RFDG, Mix and ConDG respectively). The concentration of fat in the milk was not affected (P = 0.47) by treatment and averaged 3.41 ± 0.29%. In comparison, protein in milk was higher (P = 0.05) in consuming DDGS (2.74, 2.85, 2.95 and 2.91 ± 0.12 for the C, RFDG, Mix and ConDG respectively). Although total methane was not different (P = 0.69) across treatments averaging 443.8 ± 20.6 L/d, cows consuming DDGS produced less (P = 0.01) methane per unit of milk produced (14.6, 11.3, 12.1 and 12.1 ± 0.84 kg milk/kg feed for the C, RFDG, Mix and ConDG respectively). Results of this study further support the notion that corn milling co-products may be used to replace both corn and soybean meal in dairy rations and also suggest that doing may also result in less methane per unit of milk produced.