Intake and Digestibility of Brown-Midrib Corn Silage by Lactating Dairy Cows

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Abstract
Two short trials in 2 yr evaluated brown midrib-3 (bm3) mutant (low lignin) corn silage for Holstein cows in early lactation. In trial 1, 5 Holstein cows per group (bm3 or normal genetic counterpart) were fed individually a ration of corn silage and grain (60:40, dry matter) from wk 2 through wk 8 postcalving. Cows fed the bm3 ration consumed 19% more digestible dry matter and energy as a percent of body weight than cows fed the normal ration. Digestibilities of most components were 2-4 percentage units higher for the bm3 ration. Milk yield was not different between rations, but cows fed bm3 lost less body weight. In trial 2, 5 Holstein cows per group were fed individually a ration of either bm3 or normal silage supplemented with a concentrate mix at 85:15 silage to concentrate. The concentrate mix was formulated to meet needs for protein, minerals and vitamins. Cows were on trial from wk 6 through wk 13 postcalving. All measures of daily intake of dry matter were greater for the bm3 ration while digestibilities of some components were reduced slightly. Digestible energy intake was 27% greater for the bm3 ration. Milk and milk component yields did not differ, but cows fed the bm3 ration gained more body weight. Total and individual ruminal volatile fatty acids were higher and pH lower with time after feeding for the bm3 ration.