In situ and in vitro studies with a 3 x 2 x 5 factorial arrangement of treatments with an added untreated control evaluated three enzyme preparations, two levels of enzyme, and five moisture conditions of grass forage. Enzyme preparations predominantly contained cellulase and xylanase and will be designated as enzyme 1 (E1), enzyme 2 (E2), and a 50:50 combination of E1 and E2 (E1E2). The five moisture conditions included fresh, wilted, dried and rehydrated to fresh, dried and rehydrated to wilt, and dried grass. Addition of the high level of E1E2 to dried grass improved (P < .05) in vitro DM (43.5 vs 38.7%) and NDF (31.1 vs 26.0%) disappearance (48 h incubation) compared with the control treatment. Also, IVDMD was greater (P < .05) for the low level of E1 applied to wilted grass compared with the control. No other enzyme application improved in situ or in vitro disappearance of substrate over the control. In vivo responses of enzyme treatments found most likely to be effective from degradability studies were measured using four ruminally cannulated steers in a 4 x 4 Latin square experiment. Treatments examined were E1 applied to fresh forage, then dried; E1 applied to wilted forage, then dried; E1E2 applied to dry forage immediately before feeding (E-dry), and untreated forage (control). All forage treatments were harvested as dry hay. Total diet and hay DM intakes were greater (P < .05) for the E-dry than for the control diet. Rate of in situ NDF disappearance and total tract DM and NDF digestibility were greater (P < .05) for the E-dry than for the other treatments. Ruminal fluid ammonia N concentration, total VFA concentration, and pH were not altered (P > .10) by dietary treatment. Ruminal particulate passage rate was greater (P < .05) and ruminal retention time was shorter (P < .05) for the E-dry than for the control treatment. Data from this study suggest that addition of fibrolytic enzymes to grass hay before feeding has the potential to enhance intake and digestion.

A study was conducted to examine the method of delivery of a solution containing cellulases and xylanases on the digestion of a forage-based diet. Five ruminally cannulated beef steers (536 kg BW) were randomly assigned to a control (CON) or one of four enzyme treatments in a 5 x 5 Latin square experiment. Steers were fed a 70:30 (DM basis) grass hay:barley diet. Enzyme-treated rations contained a solution of fibrolytic enzymes at the rate of 1.65 mL/kg of forage DM. Enzyme application treatments were 1) enzyme to forage 24 h before feeding (F-24), 2) enzyme to forage 0 h before feeding (F-0), 3) enzyme to barley 0 h before feeding (B-0), and 4) enzyme infused ruminally 2 h after feeding (RI). Dry matter and NDF intakes were not different (P > .10) across treatments. Ruminal pH was lower and total VFA concentration at 16 h after-feeding was greater (P < .10) for steers fed enzyme treatments compared with CON. Rate of NDF disappearance was greater (P < .05) for enzyme-treated than for untreated grass substrate. Ruminal infusion of enzymes compared with F-24 and F-0 produced lower disappearance of DM at 8 and 32 h (P < .10), NDF at 32 h (P < .10), and DM and NDF at 96 h (P < .05). Rate of DM disappearance of enzyme-treated grass hay was greater (P < .10) for steers fed B-0 than for those fed F-24 and F-0 and for CON than for F-24 and F-0. Total tract digestibility of DM, NDF, and ADF was greater (P < .10) for F-24 and F-0 than for CON. Forage transit time was shorter (P < .10) for B-0 than for F-24 and F-0; however, all other contrasts for particulate passage did not differ (P > .10). Results from this study indicate that direct application of enzymes to forages is capable of improving forage digestion.

Sixty crossbred beef steers (initial BW = 412 kg) were used in a 83-d finishing study to determine the effect of feeding dry rolled high-oil corn on performance and total-tract digestibility of finishing diets. Steers were allotted by weight to the following dietary treatments: 1) control corn (C; 82% normal corn, 12% triticale silage), 2) high-oil corn (HO; 82% high-oil corn, 12% silage), and 3) high-oil corn formulated to be isocaloric to C (ISO; 74% high-oil corn, 20% silage). Total lipid content was 4.9% (DM basis) for normal corn and 7.0% for high-oil corn. Steers were individually fed using electronic gates. Quantity of feed offered and refused was recorded daily. Fecal samples were collected on d 63 to 66 of the trial to determine digestibility. Chromic oxide was fed as an indigestible marker for 7 d before fecal collection began. Planned contrasts of HO vs C and ISO vs C were used to assess treatment differences. Dry matter intake was greater for steers fed C vs HO (P < 0.01) or C vs ISO (P < 0.01), but daily gain and feed efficiency were not affected (P > 0.05) by treatments. Digestibility of DM, OM, starch, and GE was greater (P < 0.05) for the HO diet than the C diet, but lipid digestibility did not differ among treatments (P > 0.05). The combined effect of greater GE content and digestibility resulted in greater (P < 0.01) DE content for the HO than for the C diet. Calculated DE of the corn was 8.3% greater (3.74 Mcal/kg; P < 0.01) for the HO diet and 6.5% greater (3.67 Mcal/kg; P < 0.01) for the ISO diet than the corn in the C diet (3.25 Mcal/kg). Dry matter and GE digestibility did not differ (P > 0.05) between the C and ISO diets. Steers consuming ISO had greater (P < 0.05) starch digestibility than steers fed the C diet. Although HO had higher DE, DE intake was similar (P > 0.05) for HO and C due to lower DMI for HO. These results indicate that available energy is greater from high-oil corn than from typical corn, but depressed voluntary feed intake prevented performance improvements and resulted in equal energy intakes between high-oil corn and typical corn diets.

Four Holstein cows averaging 147 DIM and fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square trial to determine diet effects on DMI, milk production, and ruminal metabolism. Diets contained either rapidly or slowly degraded NDF, referred to as low fill and high fill, respectively, combined with two percentages of nonstructural carbohydrate. Treatments were 39% nonstructural carbohydrate (low or high fill) and 29% nonstructural carbohydrate (low or high fill). Intake of DM was not affected by either fill or nonstructural carbohydrate. Ruminal NDF digestibilities averaged 43.1 and 35.6% for the low fill and high fill diets, respectively. Ruminally digested nonstructural and total carbohydrate increased, but milk production decreased, as nonstructural carbohydrate increased from 29 to 39% in diets. Liquid and solid ruminal passage rates, as measured by Co-EDTA and Yb, respectively, were reduced by either 39% nonstructural carbohydrate or low fill diets. Lower microbial N flow to the duodenum and lower efficiency of microbial growth also were observed for diets with 39% nonstructural carbohydrate. The combination of 39% nonstructural carbohydrate and rapidly degraded fiber gave the highest DM and nonstructural carbohydrate digestion in the rumen but resulted in low microbial N synthesis per day and the least microbial N per kilogram of OM digested.

Five ruminally and duodenally cannulated steers were used in a 5 x 5 Latin square design with a 2 x 2 + 1 arrangement of treatments to study the effects of barley variety and dietary barley content on digestive function in steers fed grass hay-based diets. Barley varities evaluated were Russell and Steptoe, which had bulk densities of 67.7 and 64.5 kg/hL, respectively. Supplemental treatments were as follows: corn, low Russell (Ru-lo), low Steptoe (St-lo), high Russell (Ru-hi), and high Steptoe (St-hi). Corn, Ru-lo, and St-lo were provided at 30% (DM basis) of grass hay-based diets, whereas Ru-hi and St-hi were provided at 35.5% of diet DM (equal starch content as the corn treatment). No treatment differences (P > .10) were observed for DMI, ruminal particulate passage rate, and NDF total tract digestibility. Ruminal DM and starch digestibility were greater (P < .01) for barley-containing diets than for the corn diet. Similarly, total tract DM (P < .10) and starch (P < .01) digestibility was greater for barley than for corn diets. Microbial protein and non-NH3 N flow to the small intestine were greater (P < .01) for the barley diets than for the corn diet. Starch intake (P < .01) and DM digestibility (P < .10) were greater for high- than for low-barley diets; however, differences due to barley variety were not observed (P > .10). In situ disappearance of grass hay NDF at 8 and 96 h of incubation was greater (P < .05) for barley than for corn diets. Rate of in situ disappearance of grain DM was greater (P < .01) for barley than for corn and for Russell than for Steptoe barley. Responses suggest that ruminal and total tract digestibility and protein flow to the small intestine can be increased with barley compared with corn as an energy supplement to grass hay-based diets.