Effects of brown midrib 3 mutation in corn silage on dry matter intake andproductivity of high yielding dairy cows

The effects of enhanced in vitro neutral detergent fiber (NDF) digestibilit y of corn silage on dry matter intake (DMI) and milk yield were evaluated u sing 32 Holstein cows in a crossover design with 28-d periods. At the begin ning of the experiment, cows were 89 d in milk and yielded 45.6 kg/d of mil k. Experimental diets contained either brown midrib (bm3) corn silage or is ogenic normal corn silage (control) at 44.6% of DM. The NDF digestibility e stimated by 30-h in vitro fermentation was higher for bm3 corn silage by 9. 7 units. Contents of NDF and lignin were lower for bm3 corn silage by 1.8 a nd 0.8 units, respectively. Diets were formulated to contain 19% crude prot ein and 31% NDF and to have a forage to concentrate ratio of 56:44. Daily D MI, milk yield (3.5% fat-corrected milk), and solids-corrected milk were 2. 1, 2.6, and 2.7 kg higher, respectively, for cows fed bm3 corn silage. The milk protein and lactose contents were greater for bm3 treatment, but milk fat content was not. Individual milk yield responses of the cows to bm3 tre atment were positively related to pretrial milk yield, and DMI response ten ded to be positively related to pretrial milk yield. Enhanced in vitro NDF digestibility was associated with higher energy intake, which resulted in i ncreased milk yield.