Energy utilization in lactating Jersey cows consuming a mixture of dried distillers grains and solubles and straw replacing alfalfa hay

Some forages require significant amounts of water to grow, causing the dairy industry to be dependent on a limited resource. Feeding crop residues and feed coproducts in dairy rations may represent opportunities when alfalfa is not readily available, and may reduce the 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 dried distillers grains and solubles (DDGS) and straw in replacement of alfalfa hay on milk production and energy utilization. A triplicated 4 × 4 Latin square design was used to evaluate the replacement of alfalfa hay with a coproduct mixture (COP) of wheat straw and DDGS. Animals were blocked by milk yield and randomly assigned to 1 of 4 experimental treatments as follows (proportions on a DM basis): a control diet (CON) containing 18.2% of alfalfa hay, a low-coproduct diet (LCOP) that contained 8.1% COP, a medium-coproduct diet (MCOP) that contained 16.3% COP, and a high-coproduct diet (HCOP) that contained 24.3% COP. No differences were observed for daily DMI or milk yield (mean ± SEM), 19.5 kg ± 0.60 and 29.6 kg ± 0.91, respectively. A quadratic tendency was observed, where increasing inclusion of COP up to 16.3% maintained ECM and milk fat yield but decreased these when animals were fed 24.3% COP. Total methane production decreased linearly from 429.4 to 345.0 ± 22.8 L/d from CON to HCOP diets, respectively. The digestibility of CP increased linearly from 64.0% to 70.4% ± 0.95%, and N balance increased linearly from 43.3 to 90.7 ± 15.0 g/d in animals consuming CON to HCOP diets. Total time spent ruminating was lowest in animals consuming the HCOP diet. A linear increasing tendency in digestible and metabolizable energy of 2.92 to 3.02 ± 0.041 Mcal/kg and 2.58 to 2.70 ± 0.047 Mcal/kg was observed in animals consuming CON to HCOP. The proportion of metabolizable energy from digestible energy tended to linearly increase from 88.3 to 89.4 ± 0.454 when COP was added to the diet. Results of this study indicate that alfalfa hay with a mixture of straw and DDGS can maintain milk production and DMI, but the partial or full replacement of alfalfa with the COP mixture may result in differences in energy utilization, in part driven by effects on CH₄ reduction.