Quantitative evaluation of fiber from nonforage sources used to replace alfalfa silage

The effectiveness of NDF from nonforage fiber sources was evaluated in two trials using midlactation Holsteins. Dietary NDF was added to the basal diet using either alfalfa silage or a nonforage high fiber feed. Diets were fed for 21 d. In trial 1, four amounts of alfalfa were fed. Basal milk fat percentage was 2.61% at 144 g of alfalfa NDF/kg of diet and increased linearly by .066 for each additional 1% alfalfa NDF added, up to 22.8 g of alfalfa NDF/kg of diet. Based on one amount of added nonforage fiber, the ratio of fat test increase to NDF added was .014 for brewers grains, .040 for oat hulls, and .047 for corn gluten feed. In trial 2, one amount of added alfalfa and each nonforage fiber source was used. The ratio of fat test increase to added NDF was .094 for alfalfa, .043 for brewers grains, .067 for oat hulls, .038 for corn gluten feed, .041 for beet pulp, and .044 for malt sprouts. When added to low fiber diets, NDF from the nonforage fiber sources elevated milk fat concentration approximately one-half as effectively as did NDF from alfalfa. Chewing activity was less affected by nonforage NDF than was milk fat concentration.