Effect of Grain Level and Protein Content of the Grain for Grazing Cows on Milk Composition and Yield, and Certain Blood and Rumen Constituents

Two concentrate mixtures, containing 8.3 and 22.6% crude protein, were fed at 1 kg per 1.75, 3.5, and 7.0 kg of milk produced during standardization to 48 lactating Holstein cows grazing medium-quality Bluegrass pasture. Milk was sampled for composition analyses at ten-day intervals. Jugular blood samples were taken for determination of serum protein and protein fractions, and rumen contents sampled for VFA analyses.