Full lactation response of cows fed diets with different sources and amounts of fiber and ruminal degradable protein.

Twenty Holstein cows were fed diets based on a mix of haycrop silage (immature orchardgrass or immature alfalfa) and corn silage with a conventional concentrate (primarily ground ear corn and soybean meal) or a concentrate based on by-products (primarily soyhulls, fish meal, and corn gluten meal). Diets for periods 1 (7 to 134 DIM), 2 (135 to 234 DIM), and 3 (235 to 305 DIM) were 40:10:50, 40:20:40, and 40:30:30 haycrop silage:corn silage:concentrate (DM basis), respectively. Dietary NDF ranged from 33 to 45%. The species of haycrop forage fed in combination with corn silage did not greatly affect milk production (mean = 28 kg/d), milk composition, nutrient digestibility, or DMI (expressed on a BW basis). Cows fed alfalfa gained more BW than those fed orchardgrass (.18 vs. .03 kg/d). Cows fed by-products produced similar amounts of milk, more milk fat (1.1 vs. .9 kg/d), and had higher DMI (21.4 vs. 19.6 kg/d) but lower BW gains (.03 vs. .18 kd/d) than those fed conventional concentrate. These data showed that a mix of high quality orchardgrass and corn silage is acceptable for dairy cows and that supplementation strategies are similar for diets based on orchardgrass and those based on alfalfa.