Effect of nonfiber carbohydrate level and Aspergillus oryzae fermentation extract on intake, digestion, and milk production in lactating dairy cows.

Eight multiparous, ruminally cannulated Holstein cows averaging 40 d in milk and 575 kg BW at the start of trial were in a replicated 4 x 4 Latin square arrangement (28-d periods) to determine the effects of dietary nonfiber carbohydrate (NFC) level and Aspergillus oryzae fermentation extract (AO) on intake, milk production, and nutrient digestibility. Treatments were 42 or 35% NFC and 0 or 3 g of AO per day arranged as a 2 x 2 factorial. Diets formulated to contain 21% NDF from alfalfa silage (48.4% of ration DM) and 18.5% CP were fed as total mixed rations twice daily. Alteration of dietary NFC level was by partial replacement of shelled corn and soybean meal with wheat middlings and brewers dried grains. Intake of NDF was higher (1.49 vs 1.22% of BW) for 35 than for 42% NFC diets, but DMI was lower (24.1 vs 24.9 kg/d). Milkfat percentage, ruminal pH, ammonia, acetate (moles/100 moles), and total tract digestibility of fiber were higher for 35% NFC diets; however, ruminal disappearance of DM, CP, and NDF from Dacron bags containing alfalfa hay was not affected (P > .10) by NFC level. Supplementation with AO did not affect (P > .10) DMI, milk yield, or nutrient digestion. Partial replacement of corn with high-fiber byproducts to lower dietary NFC level and correspondingly increase NDF level increased NDF intake but effected only a small change in DMI. Reducing dietary NFC level improved ruminal fermentation and milkfat percentage without significantly affecting milk yield.