The objective of this study was to evaluate the impact of maturity at harvest and dietary inclusion rate of triticale silage on the production performance and nutrient utilization of lactating dairy cows. The hypothesis was that the production performance of lactating dairy cows would increase when consuming triticale harvested and ensiled at the boot stage of maturity (BS), as compared to consuming triticale harvested and ensiled at the soft-dough stage of maturity (SDS), and that the difference would be greater in high-forage diets. A single field of triticale was planted, and harvested at the BS or SDS of maturity, and the harvested forage was ensiled in separate bunker silos. Eight primiparous and 16 multiparous Holstein cows were assigned to 1 of 4 diets in a replicated 4 × 4 Latin square design with 21-d periods. Cows were fed once daily (10:00 a.m.) using a Calan gate system (American Calan Inc., Northwood, NH). Diets included BS or SDS triticale silage with dietary forage inclusion of 54% (high-forage; HF) or 36% (low-forage; LF). Cows consuming diets containing BS silage produced more milk per day than cows consuming diets containing SDS silage. This response was observed when feeding both LF and HF diets. The maturity of the forage (BS vs. SDS) did not affect the apparent total tract digestibility of neutral detergent fiber (NDF) or the yield of energy-corrected milk. Cows consuming diets containing BS silage yielded more milk protein and lactose per day than cows consuming diets containing SDS silage, and we also observed this response when feeding both LF and HF diets. When fed the LF diets, cows had a higher apparent total-tract digestibility on CP and NDF, whereas apparent total-tract starch digestibility was higher in cows fed HF diets. Cows consuming LF diets exhibited higher levels of de novo fatty acid synthesis compared to those on HF diets. Feeding LF diets yielded more C14:1, C18:1 trans-9, and unknown fatty acids, while C16:0, C18:1 trans-10, CLA cis-9, trans-11, and CLA trans-10, cis-12 fatty acids yielded more in cows fed with SDS diets. Notably, CLA cis-9, trans-11, and CLA trans-10, cis-12 fatty acids were highest in SDS diets. Additionally, stearic fatty acid (C18:0) concentrations increased in HF diets and SDS silage. In conclusion, the study found that triticale maturity at harvest minimally affects dairy cow performance, with consistent milk production across harvest stages. While nutrient variations were observed, the conclusion emphasizes the importance of considering not only forage quality but also agronomic management and planting schedules for subsequent crops when deciding on harvest timing. / Master of Science / Cool-season or winter annual grasses, also known as small grain grasses, can be cultivated as cover crops to protect or improve the quality of the soil when the warm-season primary crop (e.g., corn) is not growing. These crops are grown during intervals between regular crop production periods. In the context of cover cropping in the United States, small grains are planted during the fall and winter seasons. One of these small grain crops is triticale, a hybrid resulting from the crossbreeding of wheat and rye. Whole plant triticale is ideal for preservation by ensiling due to its high level of water-soluble carbohydrates, low buffering capacity, and easily controllable moisture content. The objectives of this study were to evaluate the impact of harvesting maturity and dietary inclusion rate of whole plant triticale silage on milk production performance and nutrient utilization of lactating dairy cows. The hypothesis was that the production performance of lactating dairy cows would increase when consuming triticale harvested and ensiled at the boot stage of maturity (BS), as compared to consuming triticale harvested and ensiled at the soft-dough stage of maturity (SDS), which is more advanced in maturity. A single field of triticale was planted, harvested at either BS or SDS and ensiled in separate bunker silos. Twenty-four Holstein cows were grouped by days in milk and daily milk production in groups of 4 cows each, and each group was assigned to one of four experimental diets. Regardless of inclusion rate, cows consuming BS diets yielded more milk, milk protein, and lactose than did cows on SDS diets and for milk yield, we observed this response when feeding both LF and HF diets. The maturity at harvest did not affect dry matter, crude protein, neutral detergent fiber, or starch digestibility of the diets. Crude protein and neutral detergent fiber digestibility were higher in cows consuming low-forage diets than in cows consuming high-forage diets, whereas starch apparent total-tract digestibility was higher in cows fed HF diets. In conclusion, the study found that triticale maturity at harvest minimally affects dairy cow performance, with consistent milk production across harvest stages. While nutrient variations were observed, the conclusion emphasizes the importance of considering not only forage quality but also agronomic management and planting schedules for subsequent crops when deciding on harvest timing.