Influence of mechanical processing on utilization of corn silage by lactating dairy cows

We conducted three experiments to determine the influence of mechanical pro cessing on corn silage utilization by lactating dairy cows. Total mixed rat ions contained either unprocessed or processed corn silage harvested betwee n 1/4 and 3/4 milk line. In trial 1, 12 multiparous Holstein cows were used in a replicated double switchback design with 21-d periods. Intake of dry matter (DM) was increased 1.2 kg/d by processing, but milk yield was unaffe cted. Processing did not affect apparent total-tract DM digestibility, but processing tended to lower starch and corn excretion in feces and reduced c oncentration of sieved corn kernel particles in feces. In trial 2, 42 Holst ein cows were used in an 18-wk randomized complete-block design. Intake of DM and milk yield were unaffected by processing, but milk fat percent was i ncreased 0.35 percentage units by processing. Processing tended to increase total-tract digestibility of starch, but reduced organic matter, crude pro tein, and neutral detergent fiber digestibilities. In trial 3, 30 Holstein cows were used in a 15-wk randomized complete block design. There was no in fluence of mechanical processing on intake or lactation performance in this trial. Despite indications of increased starch digestion in two trials and increased DM intake in one trial, effects of processing corn silage on lac tation performance were minimal with corn silage at the maturity and moistu re contents used in these trials.