Impact of Early-Harvested Orchardgrass (Dactylis glomerata L.) Silage With Reducing the Concentrate Input on Dairy Cow Performance, Milk Production, and N Balance.

We evaluated the effects of feeding early-harvested first-cut orchardgrass (Dactylis glomerata L.) silage (EGS) instead of silage harvested at a more mature stage (LGS) while increasing forage-to-concentrate ratio on feed intake, behavior, milk production, milk fatty acids profile, and N balance in dairy cows. Six multiparous cows were used in a crossover design with two isoenergetic and isonitrogenous dietary treatments: (1) ET, containing EGS (51.5% dry matter, DM), ear corn silage (ECS; 20% DM), and concentrate (28.5% DM), and (2) LT, containing LGS (36.5% DM), ECS (20% DM), and concentrate (43.5% DM). Compared to LT, ET maintained DM intake (DMI), milk yield (fat-corrected milk [FCM] and energy-corrected milk [ECM]), and feed efficiency (FCM/DMI and ECM/DMI) and increased eating and ruminating times and milk fat content with a lower concentration of C18:1 trans-10; however, it did not affect the concentration of de novo fatty acid and milk fat yield. ET did not affect fecal, urinary, retained, or productive N compared to LT but decreased milk N. The results indicate that feeding EGS instead of LGS could be a good approach to reduce concentrate supplementation without adversely affecting milk production and N efficiency; however, it could decrease milk N utilization.