Corn Silage with Either Haycrop Silage or Hay for Lactating Cows1,2

Abstract

Eight Holstein cows were assigned randomly to two forage treatment groups receiving urea-treated corn silage (.5% urea, 27% dry matter) plus either wilted, mixed grass silage (37% dry matter) or field-cured hay (same source, cut 12 days later). Corn silage and haycrop were fed in a 60:40 dry matter ratio. A 16% (as fed) crude protein concentrate was fed to appetite until peak of lactation and according to 1966 National Research Council energy standards thereafter. Energy and nitrogen balance and ration digestibility were determined during wk 6 and 21 postpartum. Haycrop silage was higher in crude protein and minerals and lower in fiber than was hay on a dry matter basis. Nutrient digestibility and partition of dietary gross energy and nitrogen were not affected significantly by forage treatment. Metabolizable energy per unit dietary gross energy or per unit of dry matter was the same for both forage treatments. Mean daily milk was 30 and 22kg in wk 6 and 21. No forage treatment×stage of lactation interactions were significant.