In situ dry matter, protein, and fiber degradation of perennial forages.

Eight forages (alfalfa, birdsfoot trefoil, red clover, bromegrass, orchardgrass, perennial ryegrass, quackgrass, and timothy) at three maturities were evaluated for ruminal DM, CP, and NDF degradation kinetics. Duplicate dacron bags were incubated for 0, 3, 6, 10, 13, 25, 48, and 72 h in two late lactation Holstein cows fitted with ruminal cannulas over eight experimental periods. Species and maturity effects were observed for soluble, slow, and undegraded fractions; degradation rate; and ruminally degradable DM, CP, and NDF. Significant species by maturity interactions also were evident for fractions and ruminal degradabilities of DM, CP, and NDF. Legumes exhibited more extensive ruminal DM degradation than did grasses. No clear trends were evident in rate of ruminal CP degradation between legumes and grasses. Mature grasses were lowest in ruminally degradable CP. Legumes exhibited a higher undegraded fraction and faster degradation rate of slowly degraded NDF fractions, resulting in similar ruminally degraded NDF for legumes and grasses. Extensive differences in ruminal degradation kinetics existed between perennial legume and grass species and maturities. Species by maturity interactions were diverse, making categorization of degradation characteristics of legumes and grasses difficult.

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.

Carbohydrate and Aspergillus oryzae effects on intake, digestion, and milk production by dairy cows.

Six multiparous, ruminally cannulated Holstein cows (46 DIM, 584 kg of BW) and 6 primiparous Holstein cows (35 DIM, 506 kg of BW) were used in two 6 x 6 Latin squares with 21-d periods to examine the effects of level of non-fiber carbohydrate, source of fibrous carbohydrate, and Aspergillus oryzae fermentation extract on intake, digestion, and milk production. Treatments were 42 and 36% non-fiber carbohydrate; shelled corn and soybean meal were replaced partially by beet pulp and dried brewers grains or soy hulls and dried brewers grains in 36% non-fiber carbohydrate diets. These three diets then were supplemented with 0 or 3 g/d of A. oryzae. Milk production and composition and DMI were not significantly affected by level or source of carbohydrate, although intake of NDF was significantly higher for 36% non-fiber carbohydrate diets. Total tract apparent digestibilities of ADF and NDF were higher for 36% non-fiber carbohydrate diets. Supplementation with A. oryzae did not significantly affect DMI, milk production, or total tract apparent digestibilities; however, milk fat content was decreased. Partial replacement of corn with fibrous carbohydrate sources, beet pulp and soy hulls, did not adversely affect intake or milk production in early lactation cows fed alfalfa silage-based diets.