Interactions between forage and wet corn gluten feed as sources of fiber in diets for lactating dairy cows

Twelve early lactation Holstein cows (4 fistulated) were used in replicated 4 x 4 Latin squares with 4-wk periods to determine the effective neutral d etergent fiber (NDF) content of wet corn gluten feed and to measure the eff ect of forage particle size on ruminal mat consistency and passage rate of wet corn gluten feed. Diets were 1) 23.3% NDF (17.4 percentage units of NDF from alfalfa silage), 2) diet 1 plus 11.1 additional percentage units of N DF from alfalfa silage, 3) diet 1 plus 10.7 percentage units of NDF from we t corn gluten feed, and 4) 8.6 percentage units of NDF from alfalfa silage plus 8.9 percentage units of NDF from coarsely chopped alfalfa hay and 10.7 percentage units of NDF from wet corn gluten feed. The calculated effectiv e NDF factor for wet corn gluten feed, using change in milk fat concentrati on per unit change in NDF, was 0.74 compared with an assumed 1.0 for alfalf a silage. Rumination activity was measured to calculate a physically effect ive NDF factor for wet corn gluten feed, which was only 0.11 compared with 1.0 for alfalfa silage. Physically effective NDF also was determined for we t corn gluten feed by wet sieving; 22% of the particles were retained on th e 3.35-mm screen or greater. Ruminal mat consistency increased and passage rate of wet corn gluten feed decreased with added hay. The inclusion of cho pped alfalfa hay to a diet containing wet corn gluten feed increased rumina l mat consistency, rumination activity, and slowed passage rate, resulting in greater ruminal. digestion of NDF from wet corn gluten feed. Depending o n the response variable, the effectiveness of NDF from wet corn gluten feed varied from 0.11 to 0.74.