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The objective of this study was to assess the value of triticale dried distillers grains with solubles (DDGS) as a replacement for barley silage in addition to a portion of the dry-rolled barley (DRB) in a grain-based feedlot finishing diet. The trial used 160 crossbred yearling steers: 144 noncannulated (478 [+ or -] 84 kg) in a complete randomized design, and 16 ruminally cannulated (494 [+ or -] 50 kg) in a replicated 4 x 4 Latin square design. The noncannulated steers were assigned to 8 standard pens (10 per pen) and 8 pens equipped with the GrowSafe system (GrowSafe Systems Ltd., Airdrie, Alberta, Canada; 8 per pen). The cannulated steers were placed (2 per pen) in the 8 GrowSafe pens and moved between pens at 28-d intervals. Each of 4 experimental diets was fed in 2 standard and 2 GrowSafe pens. The diets contained (DM basis) 1) 85% DRB and 10% barley silage (CON); 2) 65% DRB, 20% triticale DDGS, and 10% barley silage (D-10S), 3) 65% DRB, 25% triticale DDGS, and 5% barley silage, and 4) 65% DRB, 30% triticale DDGS, and no barley silage. Supplement (5% of dietary DM) was included in all diets. Ruminal pH was measured over four 7-d periods using indwelling electrodes. Replacing barley silage with triticale DDGS linearly decreased mean ruminal pH (P = 0.006), linearly increased duration (P = 0.006 and P = 0.01) and area under the curve (P = 0.02 and P = 0.05) below pH 5.5 and 5.2, and linearly increased the frequency of subacute (P = 0.005) and acute (P = 0.05) bouts of ruminal acidosis. Variation in mean ruminal pH decreased (P = 0.008) in steers fed D-10S compared with CON. Similarly, variation in DMI was less for steers fed triticale DDGS compared with CON. Steers fed D-10S tended to have greater DMI (P = 0.08) but similar ADG and G:F compared with CON steers. Replacing barley silage with triticale DDGS tended to linearly decrease DMI (P = 0.10) and increase (P = 0.06) G:F. Compared with CON, steers fed D-10S tended to have greater backfat thickness (P = 0.10) and decreased dressing percentage (P = 0.06), ribeye area (P = 0.10), and meat yield (P = 0.06). Severity and number of abscessed livers was greater (P = 0.006) in steers fed D-10S compared with those fed CON. Although mean ruminal pH decreased as barley silage was replaced with triticale DDGS, the trend for improved growth suggests that reduced ruminal pH did not affect animal performance. Triticale DDGS can be substituted for barley silage in finishing diets in addition to a portion of barley grain without affecting growth performance or carcass quality, but it is recommended that an antimicrobial be included in the diet to reduce liver abscesses. Key words: acidosis, barley silage, dried distillers grains with solubles, eating behavior, feedlot finishing diet, forage substitution doi: 10.2527/jas.2009-2703

Cinnamaldehyde (CIN), a natural chemical compound found in the bark of cinnamon trees, can alter rumen fermentation by inhibiting selected ruminal microbes, and consequently, may improve growth performance and feed efficiency of anireals. The objective of this study was to evaluate the effects of supplementing the diet of feedlot cattle with CIN on intake, growth performance, carcass characteristics, and blood metabolites. Seventy yearling steers (BW = 390 [+ or -] 25.2 kg) were assigned to a randomized complete block design with 5 treatments: control (no additive), monensin (MO; 330 mg x [steer.sup.-1] x [d.sup.-1]), and 400, 800, or 1,600 mg of CIN x [steer.sup.-1] x [d.sup.-1]. At the start of the experiment, steers were blocked according to BW and assigned to 14 blocks of 5 cattle, with cattle within block assigned to treatments. The diets consisted of 9% barley silage, 86% dry-rolled barley grain, and 5% supplement (DM basis). Dry matter intake responded quadratically (P = 0.03) to CIN supplementation with 13% more feed consumed for steers fed CIN (mean of 3 CIN levels) compared with those fed control during the first 28 d of the experiment, and with a tendency of 4% increase over the entire experiment. The ADG (kg/d) tended to respond quadratically (P = 0.08) to CIN supplementation during the first 28 d, but was not affected over the entire experiment (112 d). Feed efficiency (G:F) linearly declined (P = 0.03) during the first 28 d with CIN supplementation and was quadratically affected between d 29 to 56 and d 85 to 112 by CIN dose. Supplementation of MO did not affect (P > 0.15) DMI or growth performance at any time during the experiment. Serum NEFA concentrations were reduced (P = 0.05) by 35, 29, 30, and 22%, respectively, on d 56, 84, 112, and overall with CIN supplementation. Concentrations of serum amyloid A were reduced on d 28 by 56, 60, or 56% for 800 mg of CIN, 1,600 mg of CIN, and MO, respectively, compared with control. Plasma concentrations of lipopolysaccharide binding protein were linearly decreased (P = 0.05) with increasing CIN supplementation on d 28. Results indicate that supplementing a feedlot finishing diet with a small dose of CIN ameliorated feed intake during the initial month but had minimal effects on ADG, feed efficiency, and carcass traits over the entire experiment. Including CIN in the diet of feedlot cattle, particularly early in the feeding period, may help promote intake and reduce the effects of stress. Key words: blood metabolite, carcass, cinnamaldehyde, growth, steer doi:10.2527/jas.2008-1608

The objective of this study was to determine if cinnamaldehyde (CIN) could be used to improve feed intake, digestion, and immune status in growing beef heifers fed high-concentrate diets. The experiment was designed as a 4 x 4 Latin square using 4 ruminally and duodenally cannulated beef heifers with 4 treatments: control (no CIN added), 400 mg/d of CIN (low), 800 mg/d of CIN (medium), and 1,600 mg/d of CIN (high), and four 21-d periods. Feed intake, rumen pH and fermentation characteristics, site and extent of digestion, microbial N synthesis, blood metabolites, and acute phase protein response were measured. The diets consisted of 15% barley silage, 80% dry-rolled barley grain, and 5% supplement (DM basis). Intakes (kg/d) of DM, OM, NDF, starch, and N were quadratically (P = 0.04) changed with increasing CIN supplementation. The amount of OM fermented in the rumen quadratically (P = 0.02) decreased with increasing CIN. Digestibilities (% of intake) of OM, NDF, and N in the rumen were not affected by supplementing with low and medium CIN, but they were reduced by 8% (P = 0.10), 31% (P = 0.05), and 17% (P = 0.05), respectively, with high CIN. Similarly, digestibilities of OM and NDF in the total tract also tended to be reduced by 7% (P = 0.10) and 20% (P = 0.10), respectively, with high CIN because supplementation of CIN had minimal effects on intestinal digestibility. Flows (g/d) of microbial N and other nutrients to the duodenum were not affected by CIN supplementation, even though the amount of ruminal fermented OM varied with level of CIN supplementation. Rumen pH, total VFA concentration, and molar proportions of individual VFA were not affected by CIN. Although concentrations of NEFA (P = 0.06) and triglyceride (P = 0.01) were quadratically changed with increasing CIN supplementation, blood concentrations of glucose and urea N, white blood cell counts, serum amyloid A, and lipopolysaccharide in plasma were not affected by CIN. Plasma haptoglobin numerically (P = 0.11) decreased with the medium dose of CIN fed compared with control. The results indicate that supplementation of a high-concentrate diet with a low dose of CIN resulted in small increases in nutrient availability in the rumen due to increased feed intake and greater ruminal digestion of OM. However, feed intake and ruminal digestion of feeds were adversely affected when a high dose of CIN was used. Key words: beef heifer, blood metabolite, cinnamaldehyde, digestibility, rumen fermentation doi: 10.2527/jas.2008-1652

The objective of this investigation was to study the effects of feeding backgrounding and finishing diets on selected acute phase proteins in the plasma of feedlot steers. Two groups of 12 steers each, at the backgrounding and finishing stages, were offered either a backgrounding (45% barley grain-based concentrate and 55% barley silage on a DM basis) or a finishing (91% barley grain-based concentrate and 9% barley silage) diet for 12 and 15 wk, respectively. Steers at the backgrounding and finishing stages had initial BW of approximately 250 and 380 kg, respectively, at the beginning of the experiment. Blood samples were obtained from a jugular vein at 3-wk intervals during the experimental period beginning at wk 3 or 0 for the backgrounding and finishing periods, respectively. Plasma samples were analyzed for serum amyloid A (SAA), lipopolysaccharide-binding protein (LBP), haptoglobin, and [[alpha].sub.1]-acid glycoprotein. Steers fed the finishing diet showed peak plasma SAA, LBP, and haptoglobin within 3 wk from the initiation of the diet (20, 23, and 1,940 [micro]g/mL for SAA, LBP, and haptoglobin, respectively). Although plasma [[alpha].sub.1]-acid glycoprotein reached a peak concentration (449 [micro]g/mL) at the beginning of the finishing phase, no diet effect was obtained for this variable. Steers fed the backgrounding diet showed less variation in the concentrations of plasma acute phase proteins measured; plasma haptoglobin reached a peak concentration (1,720 [micro]g/mL) 9 wk after the beginning of this diet. In conclusion, feeding feedlot steers the backgrounding or finishing diet was associated with increased peak concentrations of acute phase proteins in the plasma. More research is warranted to elucidate the mechanisms behind the inflammatory responses observed in feedlot steers and their implications for health issues and the production efficiency of feedlot operations. Key words: acute phase protein, barley grain, cattle, feedlot

In vitro experiments were conducted to examine the characteristics and mode of action of a protease that increased the ruminal fiber digestibility of alfalfa hay. A commercial source of protease (Protex 6L, Genencor Int., Rochester, NY), already characterized for its main activities, was further analyzed to determine protease activity in response to pH, molecular size by SDS-PAGE, specificity to degrade model or feed substrates, response to autoclaving, and action of specific protease inhibitors in the absence or presence of ruminal fluid. In addition, batch culture in vitro incubations in buffered ruminal fluid were conducted to compare the enzyme product with purified protease sources, and dose-response studies (0 to 10 [micro]L/g of forage DM) were carried out using alfalfa hay as a substrate. The enzyme product was shown to be an alkaline protease (optimum pH >8.5) of approximately 30 kDa. Specificity in the absence of ruminal fluid showed that the enzyme was active against gelatin and casein to the same extent, whereas it had limited (21% of the total) activity on BSA. In the presence of ruminal fluid and with the use of feed substrates, the protease increased (P < 0.05) 22-h IVDMD (%) of alfalfa hay, fresh corn silage, dry-rolled corn, and a total mixed ration composed of the 3 ingredients (39.5 vs. 44.7; 50.3 vs. 54.5; 63.8 vs. 68.4; and 55.4 vs. 56.4 for control vs. protease for each feed, respectively). Inhibitor studies in the absence of ruminal fluid indicated that the enzyme was inhibited most by a serine protease inhibitor but not by cysteineor metalloprotease inhibitors (10 vs. 1.9 and 0.1%, respectively). In the presence of ruminal fluid, the serine protease inhibitor reversed (P < 0.05) the increase in alfalfa IVDMD achieved by the enzyme product, such that IVDMD was similar to that of the control treatment. Comparisons among different proteases revealed that only pure subtilisin achieved increases in IVDMD that were similar to those with protease, suggesting the serine protease was subtilisin-like (EC 3.4.1.62). Dose-response studies using alfalfa hay as substrate showed quadratic responses in IVDMD, NDF digestion, and hemicellulose and protein disappearance. It is postulated that this enzyme acts by removing structural proteins in the cell wall, allowing ruminal microbes to gain faster access to digestible substrates. Key words: exogenous protease, fiber, in vitro disappearance, rumen digestibility

Our objective was to determine if condensed tannin extract from quebracho trees (Schinopsis quebracho-colorado; red quebracho) could be used to reduce enteric methane emissions from cattle. The experiment was designed as a repeated 3 x 3 Latin square (4 squares) with 3 treatments (0, 1, and 2% of dietary DM as quebracho tannin extract) and 3 28-d periods. Six spayed Angus heifers (238 [+ or -] 13.3 kg of initial BW) and 6 Angus steers (207 [+ or -] 8.2 kg of initial BW) were each assigned to 2 squares. The measured condensed tannin content of the extract was 91%, and the basal diet contained 70% forage (DM basis). Feeding quebracho tannin extract had no effect on BW, ADG, or nutrient intakes. Furthermore, it had no effect on DM, energy, or fiber (ADF and NDF) digestibility, but apparent digestibility of CP decreased linearly (P < 0.001) by 5 and 15% with 1 and 2% quebracho tannin extract, respectively. There were no effects of quebracho tannin extract on methane emissions (g/d, g/kg of DM, % of GE intake, or % of DE intake). Feeding up to 2% of the dietary DM as quebracho tannin extract failed to reduce enteric methane emissions from growing cattle, although the protein-binding effect of the quebracho tannin extract was evident. Key words: beef cattle, condensed tannin, greenhouse gas, methane

Two experiments were conducted to investigate the effects of oral supplementation of the lactic-acid-producing bacterium Enterococcus faecium EF212 alone or in combination with Saccharomyces cerevisiae (yeast) on mediators of the acute phase response in feedlot steers. Eight fistulated steers were used to study the effects of E. faecium alone or with yeast in a crossover design with 2 Latin squares, 4 steers within each square, and 2 periods. The length of each period was 3 wk, with a 10-d adaptation and an 11-d measurement period. The experimental diet contained 87% steam-rolled barley, 8% whole-crop barley silage, and 5% supplement (DM basis). In Exp. 1, treatments were control vs. the lactic-acid-producing bacterium E. faecium (6 x [10.sup.10] cfu/d). In Exp. 2, treatments were control vs. E. faecium (6 x [10.sup.10] cfu/d) and S. cerevisiae (6 x [10.sup.10] cfu/d). The bacteria and yeast supplements were blended with calcium carbonate to supply 6 x [10.sup.10] cfu/ d when top-dressed into the diet once daily at the time of feeding (10 g/d). Steers fed the control diet received only carrier (10 g/d). Blood samples were collected from the jugular vein on d 17 and 21 of each period, and serum amyloid A (SAA), lipopolysaccharide binding protein (LBP), haptoglobin, and alphal-acid glycoprotein ([[alpha].sub.l]-AGP) were measured. Supplementation of feed with E. faecium had no effect on concentrations of SAA, LBP, haptoglobin, or [[alpha].sub.1]-AGP in plasma compared with those of controls. However, feeding E, faecium and yeast increased (P = 0.02) plasma concentrations of SAA, LBP, and haptoglobin but had no effect on plasma [[alpha].sub.1]-AGP. In conclusion, oral supplementation of E. faecium alone had no effect on the mediators of the acute phase response that were measured, whereas feeding of E. faecium and yeast induced an inflammatory response in feedlot steers fed high-grain diets. Further research is warranted to determine the mechanism(s) by which E. faecium and yeast stimulated production of acute phase proteins in feedlot steers. Key words: acute phase protein, direct-fed microbial, feedlot steer, probiotic, yeast

The objective of this study was to identify feed additives that reduce enteric methane emissions from cattle. We measured methane emissions, total tract digestibility (using chromic oxide), and ruminal fermentation (4 h after feeding) in growing beef cattle fed a diet supplemented with various additives. The experiment was designed as a replicated 4 x 4 Latin square with 21-d periods and was conducted using 16 Angus heifers (initial BW of 260 [+ or -] 32 kg). Treatments were: control (no additive), fumaric acid (175 g/d) with sodium bicarbonate (75 g/d), essential oil and spice extract (1 g/d), or canola oil (4.6% of DMI). The basal diet consisted of 75% whole-crop barley silage, 19% steamrolled barley, and 6% supplement (DM basis). Four large chambers (2 animals fed the same diet per chamber) were equipped to measure methane emissions for 3 d each period. Adding canola oil to the diet decreased (P = 0.009) total daily methane emissions by 32% and tended (P = 0.09) to decrease methane emissions as a percentage of gross energy intake by 21%. However, much of the reduction in methane emissions was due to decreased (P < 0.05) feed intake and lower (P < 0.05) total tract digestibility of DM and fiber. Digestibility of all nutrients was also lowered (P < 0.05) by feeding essential oil, but there were no effects on ruminal fermentation or methane emissions. In contrast, adding fumaric acid to the diet increased total VFA concentration (P = 0.03), increased propionate proportions (P = 0.01), and decreased the acetate:propionate ratio (P = 0.002), but there was no measurable effect on methane emissions. The study demonstrates that canola oil can be used to reduce methane losses from cattle, but animal performance may be compromised due to lower feed intake and decreased fiber digestibility. Essential oils had no effect on methane emissions, whereas fumaric acid caused potentially beneficial changes in ruminal fermentation but no measurable reductions in methane emissions. Key words: beef cattle, canola oil, essential oil, fumaric acid, greenhouse gas, methane

The effects of grain adaptation protocol on subacute acidosis and feed intake by cattle were studied in a completely randomized experiment using 12 crossbred heifers (384 [+ or -] 25 kg BW). The dietary proportion of concentrate was increased from 40 to 90% (DM basis) either by rapid adaptation (65% concentrate diet fed for 3 d) or by gradual adaptation (five intermediate diets containing 48.3, 56.7, 65.0, 73.3, and 81.7% concentrate, fed for 3 d each). Feed intake and ruminal pH (by indwelling ruminal electrodes) were monitored over 20 d. Mean daily pH variables did not differ (P [greater than or equal to] 0.10) between treatments on any of the 3 or 4 d that 65 or 90% concentrate was fed. Variances of a number of pH variables were greater (P < 0.05) for rapidly adapted heifers than for those on the gradual adaptation protocol during adaptation to 65 and 90% concentrate. Mean hourly pH did not differ over the first 24 h of adaptation to 65% concentrate, but variance of hourly pH tended (P < 0.10) to be greater for rapidly adapted than for gradually adapted heifers for eight of the first 24 h. On the first day of feeding 90% concentrate, ruminal pH tended (P = 0.07) to be less at 11 and 12 h after feeding with rapid adaptation than with gradual adaptation. Variance of hourly pH increased steadily in rapidly adapted heifers from 6 h after feeding onward. Ruminal VFA concentration and osmolality did not differ between treatments. Ruminal lactate concentration was Key Words: Acidosis, Concentrate, Grain Adaptation, Ruminal pH, Volatile Fatty Acids

Methane emitted from the livestock sector contributes to greenhouse gas emissions worldwide. Understanding the variability in enteric methane production related to diet is essential to decreasing uncertainty in greenhouse gas emission inventories and to identifying viable greenhouse gas reduction strategies. Our study focused on measuring methane in growing beef cattle fed corn- or barley-based diets typical of those fed to cattle in North American feedlots. The experiment was designed as a randomized complete block (group) design with two treatments, barley and corn. Angus heifer calves (initial BW = 328 kg) were allocated to two groups (eight per group), with four cattle in each group fed a corn or barley diet. The experiment was conducted over a 42-d backgrounding phase, a 35-d transition phase and a 32-d finishing phase. Backgrounding diets consisted of 70% barley silage or corn silage and 30% concentrate containing steam-rolled barley or dry-rolled corn (DM basis). Finishing diets consisted of 9% barley silage and 91% concentrate containing barley or corn (DM basis). All diets contained monensin (33 mg/kg of DM). Cattle were placed into four large environmental chambers (two heifers per chamber) during each phase to measure enteric methane production for 3 d. During the backgrounding phase, DMI was greater by cattle fed corn than for those fed barley (10.2 vs. 7.6 kg/d, P < 0.01), but during the finishing phase, DMI was similar for both diets (8.3 kg/d). The DMI was decreased to 6.3 kg/d with no effect of diet or phase while the cattle were in the chambers; thus, methane emissions (g/d) reported may underestimate those of the feedlot industry. Methane emissions per kilogram of DMI and as a percentage of GE intake were not affected by grain source during the backgrounding phase (24.6 g/kg of DMI; 7.42% of GE), but were less (P < 0.05) for corn than for barley during the finishing phase (9.2 vs. 13.1 g/kg of DMI; 2.81 vs. 4.03% of GE). The results indicate the need to implement dietary strategies to decrease methane emissions of cattle fed high-forage backgrounding diets and barley-based finishing diets. Mitigating methane losses from cattle will have long-term environmental benefits by decreasing agriculture's contribution to greenhouse gas emissions. Key Words: Barley, Beef Cattle, Carbon Dioxide, Corn, Greenhouse Gases, Methane

Methane emitted from the livestock sector contributes to greenhouse gas (GHG) emissions. Understanding the effects of diet on enteric methane production can help refine GHG emission inventories and identify viable GHG reduction strategies. Our study focused on measuring methane and carbon dioxide emissions, total-tract digestibility, and ruminal fermentation in growing beef cattle fed a diet supplemented with various additives or ingredients. Two experiments, each designed as a 4 x 4 Latin square with 21-d periods, were conducted using 16 Holstein steers (initial BW 311.6 [+ or -] 12.3 kg). In Exp. 1, treatments were control (no additive), monensin (Rumensin, Elanco Animal Health, Indianapolis, IN; 33 mg/kg DM), sunflower oil (400 g/d, approximately 5% of DMI), and proteolytic enzyme (Protex 6-L, Genencor Int., Inc., CA; 1 mL/kg DM). In Exp. 2, treatments were control (no additive), Procreatin-7 yeast (Prince Agri Products, Inc., Quincy, IL; 4 g/d) Levucell SC yeast (Lallemand, Inc., Rexdale, Ontario, Canada; 1 g/d), and fumaric acid (Bartek Ingredients Inc., Stoney Creek, Ontario, Canada; 80 g/d). The basal diet consisted of 75% barley silage, 19% steam-rolled barley grain, and 6% supplement (DM basis). Four large chambers (two animals per chamber) were equipped with lasers and infrared gas analyzers to measure methane and carbon dioxide, respectively, for 3 d each period. Total-tract digestibility was determined using chromic oxide. Approximately 6.5% of the GE consumed was lost in the form of methane emissions from animals red the control diet. In Exp. 1, sunflower oil decreased methane emissions by 22% (P = 0.001) compared with the control, whereas monensin (P = 0.44) and enzyme had no effect (P = 0.82). However, oil decreased (P = 0.03) the total-tract digestibility of NDF by 20%. When C[H.sub.4] emissions were corrected for differences in energy intake, the loss of GE to methane was decreased by 21% (P = 0.002) using oil and by 9% (P = 0.09) using monensin. In Exp. 2, Procreatin-7 yeast (P = 0.72), Levucell SC yeast (P = 0.28), and fumaric acid (P = 0.21) had no effect on methane emissions, although emissions as a percentage of GE intake were 3% (nonsignificant, P = 0.39) less for steers fed Procreatin-7 yeast compared with the control. This study demonstrates that sunflower oil, ionophores, and possibly some yeast products can be used to decrease the GE lost as methane from cattle, but fiber digestibility is impaired with oil supplementation. Key Words: Beef Cattle, Carbon Dioxide, Feed Additives, Greenhouse Gases, Methane

Research was conducted to determine whether fluctuations in the amount of feed delivered and timing of feeding affect ruminal pH and growth of feedlot cattle. In Exp. 1, the effects of constant (C) vs. fluctuating (F) daily feed delivery on ruminal pH were assessed in a crossover experiment (two 28-d periods) involving six mature, ruminally cannulated steers. The diet consisted of 86.8% barley grain, 4.9% supplement, and 8.3% barley silage (DM basis) and was offered ad libitum for 2 wk to estimate DMI by individual steers. Steers in group C were offered a constant amount of feed daily equal to their predetermined DMI, whereas steers in group F were offered 10% more or less than their predetermined DMI on a rotating 3-d schedule. Ruminal pH of each steer was measured continuously via an indwelling electrode placed in the rumen during the last 6 d of each period. Mean pH tended to be lower (0.10 units) for F than C (5.63 vs. 5.73; P = 0.15), and ruminal pH of steers in group F tended to remain below 5.8 (P = 0.03) or 5.5 (P = 0.14) for greater proportions of the day than steers in group C. Inconsistent delivery of feed lowered ruminal pH, suggesting increased risk of subclinical acidosis. In Exp. 2, a 2 x 2 factorial was used to study the effects of pattern (C vs. F) and feeding time (morning [0900] vs. evening [2100]) on the feeding behavior and performance of 234 (310 [+ or -] 23 kg) Charolais x Hereford beef steers during backgrounding and finishing phases over 209 d. One pen per treatment was equipped with a radio frequency identification (GrowSafe Systems Ltd., Airdrie, Canada) system that monitored bunk attendance by each steer throughout the trial. Pattern of feed delivery did not affect (P = 0.16) DMI (7.36 kg/d), ADG (1.23 kg/d), G:F (0.17), or time spent at the bunk (141 ruin/d), nor were pattern of feed delivery x time of feeding interactions observed (P = 0.18). Late feeding increased (P < 0.05) daily DMI (7.48 vs. 7.26 kg), ADG (1.28 vs. 1.00 kg/d), and G:F (0.21 vs. 0.15). These studies indicate that the risk of subclinical acidosis was increased with fluctuating delivery of feed, but the greater risk of acidosis did not impair growth performance by feedlot cattle. Consequently, daily intake fluctuations of 10% DMI or less that do not alter overall intake by feedlot cattle are unlikely to have any negative consequences on growth performance. Key Words: Behavior, Cattle, Intake Fluctuation, performance, Ruminal pH

A dual-flow continuous culture system was used to investigate the effects of pH and addition of an enzyme mixture to a total mixed ration (TMR) on fermentation, nutrient digestion, and microbial protein synthesis. A 4 x 4 Latin square design with a factorial arrangement of treatments was used, with four 9-d periods consisting of 6 d for adaptation and 3 d for measurements. Treatments were as follows: 1) high pH with control TMR, 2) high pH with TMR treated with enzyme, 3) low pH with control TMR, and 4) low pH with TMR treated with enzyme. Ranges of pH were 6.0 to 6.6 and 5.4 to 6.0 for high and low, respectively. Fermenters were fed twice daily a TMR consisting of 30% alfalfa hay, 30% corn silage, and 40% rolled corn (DM basis). The silage was milled fresh and the TMR was fed to the fermenters in fresh form (64% DM). The enzyme mixture was a commercial product of almost exclusive protease activity; it was applied daily to the fresh TMR and stored at 4[degrees]C for at least 12 h before feeding. Degradability of OM, NDF, ADF, and cellulose was decreased (P < 0.05) by low pH. Hemicellulose and protein degradation were not affected by pH. Enzyme addition increased (P < 0.01) NDF degradability (by 43% and 25% at high and low pH, respectively), largely as a result of an increase in hemicellulose degradation (by 79% and 51% at high and low pH, respectively). This improvement was supported by an increase (P < 0.05) in the xylanase and cellulase activities in the liquid phase of the fermenter contents. Total VFA were decreased (P < 0.05) by low pH, but were not affected by enzyme addition. Total bacterial numbers were increased (P < 0.03) at low pH and tended (P < 0.13) to increase with enzyme addition. Cellulolytic bacteria in effluent fluid were decreased (P < 0.02) at low pH but were unaffected by enzyme addition. Despite a large increase (P < 0.001) in protease activity, protein degradation was only numerically increased by enzyme addition. Microbial protein synthesis was higher (P < 0.10) at high pH but was not affected by enzyme addition. Methane production, expressed as a proportion of total gases, was decreased (P < 0.001) at low pH but was not affected by enzyme addition. It is concluded that it is possible to adapt the continuous culture system to use fresh feeds instead of dried feeds. Overall, the results indicate that the enzyme product used in this study has a potential to increase fiber degradability without increasing methane production. Key Words: Digestion, Enzymes, pH, Rumen Fermentation

With the objective of developing a rational approach for the selection of feed enzymes for ruminants, 22 commercial enzyme products were examined in terms of protein concentration, enzymic activities on model substrates, and hydrolytic capacity, the latter determined from the release of reducing sugars from alfalfa hay and corn silage. An in vitro ruminal degradation assessment was carried out using the same substrates, untreated or treated with the 22 enzyme products at 1.5 [micro]L/g forage DM. Stepwise regressions were then performed to establish relationships between these factors. Protein concentration and enzymic activities explained at least 84% (P < 0.01) of the variation in the release of reducing sugars from alfalfa and corn silage. Alfalfa DM degradation after incubation with ruminal fluid for 18 h was positively related to xylanase activity ([R.sup.2] = 0.29, P < 0.01), but the same activity was negatively related to DM degradation of corn silage ([R.sup.2] = 0.19, P < 0.05). Protease activity explained a further 10% of the alfalfa DM degradation (P < 0.10). Following sequential steps involving the determination of rate and extent of DM and fiber degradation, the best candidates for alfalfa and corn silage were selected. Enzyme products effective with alfalfa hay seemed to exert part of their effect during the pretreatment period, whereas enzymes effective with corn silage worked exclusively after ruminal fluid was added. This finding suggests that different modes of action of exogenous enzymes are attacking different substrates and may partly explain enzyme-feed specificity. In alfalfa, it seems that effective enzymes work by removing structural barriers that retard the microbial colonization of digestible fractions, increasing the rate of degradation. In corn silage, effective enzymes seem to interact with ruminal enzymes to degrade the forage more rapidly, which is consistent with previous findings of synergism between exogenous and ruminal enzymes. Key Words: Degradation, Enzymes, Fiber, Ruminants, Screening

Two studies were conducted to determine whether a bacterial direct-fed microbial (DFM) alone or with yeast could minimize the risk of acidosis and improve feed utilization in feedlot cattle receiving high-concentrate diets. Eight ruminally cannulated steers, previously adapted to a high-concentrate diet, were used in crossover designs to study the effects of DFM on feed intake, ruminal pH, ruminal fermentation, blood characteristics, site and extent of digestion, and microbial protein synthesis. Steers were provided ad libitum access to a diet containing steam-rolled barley, barley silage, and a protein-mineral supplement (87, 8, and 5% on a DM basis, respectively). In Exp. 1, treatments were control vs. the lactic-acid producing bacterium Enterococcus faecium EF212 (EF; 6 x [10.sup.9] cfu/d). In Exp. 2, treatments were control vs EF (6 x [10.sup.9] cfu/d) and yeast (Saccharomyces cerevisiae; 6 x [10.sup.9] cfu/d). Supplementing feedlot cattle diets with EF in Exp. 1 increased (P < 0.05) propionate and (P < 0.05) decreased butyrate concentrations, decreased the nadir of ruminal pH (P < 0.05), enhanced the flow of feed N (P < 0.10) to the duodenum but reduced that of microbial N (P < 0.10), reduced (P < 0.10) intestinal digestion of NDF, and increased (P < 0.10) fecal coliform numbers. Other than the increase in propionate concentrations that signify an increase in energy precursors for growth, the other metabolic changes were generally considered to be undesirable. In Exp. 2, providing EF together with yeast abolished most of these undesirable effects. Combining EF with yeast increased the DM digestion of corn grain incubated in sacco, but there were no effects on altering the site or extent of nutrient digestion. The diets used in this study were highly fermentable, and the incidence of subclinical ruminal acidosis, defined as steers with ruminal pH below 5.5 for prolonged periods of time, was high. Supplementing the diet with EF, with or without yeast, had limited effects on reducing ruminal acidosis. It seems that cattle adapted to high-grain diets are able to maintain relatively high feed intake and high fiber digestion despite low ruminal pH. The Enterococcus faecium bacterium and yeast used in this study were of limited value for feedlot cattle already adapted to high-grain diets. Key Words: Acidosis, Enterococcus, Microbial Flora, Probiotics, Yeasts

A series of in vitro studies was conducted to determine the effects of adding a commercial enzyme product on the hydrolysis and fermentation of cellulose, xylan, and a mixture (1:1 wt/wt) of both. The enzyme product (Liquicell 2500, Specialty Enzymes and Biochemicals, Fresno, CA) was derived from Trichoderma reesei and contained mainly xylanase and cellulase activities. Addition of enzyme (0.5, 2.55 and 5.1 [micro]L/g of DM) in the absence of ruminal fluid increased (P < 0.001) the release of reducing sugars from xylan and the mixture after 20 h of incubation at 20[degrees]C. Incubations with ruminal fluid showed that enzyme (0.5 and 2.55 [micro]L/g of DM) increased (P < 0.05) the initial (up to 6 h) xylanase, endoglucanase, and [beta]-D-glucosidase activities in the liquid fraction by an average of 85%. Xylanase and endoglucanase activities in the solid fraction also were increased (P < 0.05) by enzyme addition, indicating an increase in fibrolytic activity due to ruminal microbes. Gas production over 96 h of incubation was determined using a gas pressure measurement technique. Incremental levels of enzyme increased (P < 0.05) the rate of gas production of all substrates, suggesting that fermentation of cellulose and xylan was enzyme-limited. However, adding the enzyme at levels higher than 2.55 [micro]L/g of DM failed to further increase the rate of gas production, indicating that the maximal level of stimulation was already achieved at lower enzyme concentrations. It was concluded that enzymes enhanced the fermentation of cellulose and xylan by a combination of pre- and postincubation effects (i.e., an increase in the release of reducing sugars during the pretreatment phase and an increase in the hydrolytic activity of the liquid and solid fractions of the ruminal fluid), which was reflected in a higher rate of fermentation. Key Words: Cellulose, Enzymes, Fermentation, Rumen, Xylan

Effects of the extent of grain processing and the percentage of silage in barley-based feedlot diets on microbial protein synthesis and nutrient digestibility were evaluated using four steers (initial BW of 442 [+ or -] 15 kg) with ruminal and duodenal cannulas. The experiment was a 4 x 4 Latin square with four periods of 21 d each. Dietary treatments were arranged as a 2 x 2 factorial with two levels of barley silage (20 and 5% DM basis) and two degrees of barley grain processing (coarsely and flatly steamrolled to a processing index [PI] of 86 and 61%, respectively). The PI was quantified as the volume weight of the barley grain after processing, expressed as a percentage of the volume weight prior to processing. Digesta flow (Yb) and microbial ([sup.15]N) markers were continuously infused into the rumen for a period of 13 d. Ruminal, duodenal, and fecal samples were collected at various times over the last 6 d of marker infusion. Diurnal ruminal pH was measured for 48 h. Intake of DM averaged 1.8% of BW, and was not different among the dietary treatments (P > 0.10). Ruminal starch digestibility was higher (P < 0.05) for the more extensively processed grain and tended (P < 0.10) to be highest when the more extensively processed grain was combined with 5% barley silage. In contrast, ruminal fiber digestibility for the 5% silage diets was reduced (P < 0.05) when the grain was more extensively processed. There was, however, no effect of grain processing on ruminal OM digestibility (P > 0.10), and hence, no inhibitory effect on microbial N flow to the intestine (P > 0.10). There was also no effect of the level of silage on microbial N flow (P > 0.10), but there was a tendency for improved efficiency of microbial protein synthesis for the 20% silage diets (P = 0.072). Ruminal escape of nonmicrobial N (P = 0.003) was greater, and thus, protein flow to the intestine was greater for the 5% silage diets. Diurnal ruminal pH was lower (P < 0.05) for 11 of the 24 hourly time points in steers fed the 5% silage diets than those fed the 20% silage diets. In conclusion, barley grain rolled to a PI of 86 to 61% and combined with 20 and 5% barley silage had little effect on microbial protein supply. Microbial protein supply was not inhibited when the barley grain was extensively processed (PI of 61%) and the silage was limited to only 5% of the diet DM, but feed intake of steers in this study was lower than would be expected in the feedlot. Key Words: Barley, Beef Cattle, Digestibility, Grain, Microbial Protein, Silage

A study was conducted to determine whether bacterial direct-fed microbials (DFM) could be used to minimize the risk of acidosis in feedlot cattle receiving high concentrate diets. Six ruminally cannulated steers, previously adapted to a high concentrate diet, were used in a double 3 x 3 Latin square to study the effects of DFM on feed intake, ruminal pH, and ruminal and blood characteristics. Steers were provided ad libitum access to a diet containing steam-rolled barley, barley silage, and a protein-mineral supplement at 87, 9, and 4% (DM basis), respectively. Treatments were as follows: control, Propionibacterium P15 (P15), and Propionibacterium P15 and Enterococcus faecium EF212 (PE). The bacterial treatments ([10.sup.9] cfu/g) plus whey powder carrier, or whey powder alone for control, were top-dressed once daily at the time of feeding (10 g/[steer/d]). Periods consisted of 2 wk of adaptation and 1 wk of measurements. Ruminal pH was continuously measured for 6 d using indwelling electrodes. Dry matter intake and ruminal pH (mean, minimum, hours, and area pH < 5.8 or < 5.5) were not affected by treatment (P > 0.05). However, supplementation with P15 increased protozoal numbers (P < 0.05) with a concomitant increase in ruminal N[H.sub.3] concentration (P < 0.01) and a decrease in the number of amylolytic bacteria (P < 0.05) compared with the control. Streptococcus bovis, enumerated using a selective medium, was numerically reduced with supplementation of PE. Although blood pH and blood glucose were not affected by DFM supplementation, steers fed PE had numerically lower concentrations of blood [CO.sub.2] than control steers, which is consistent with a reduced risk of metabolic acidosis. Although the bacterial DFM used in this study did not induce changes in DMI or ruminal and blood pH, some rumen and blood variables indicated that the bacterial DFM used in this study may decrease the risk of acidosis in feedlot cattle. Key Words: Acidosis, Beef Cattle, Enterococcus, Microbial Flora, Probiotics, Propionibacterium

We conducted a study to determine the effects of treating barley grain with a fibrolytic enzyme mixture on chewing activities, ruminal fermentation, and total tract digestibility in cattle. We also investigated the potential benefits of using barley straw rather than barley silage as a roughage source in high-grain diets for feedlot cattle. Steers were given ad libitum access to one of four diets that consisted of 95% barley-based concentrate and 5% forage (DM basis). The concentrate was either control or enzymetreated, and the forage was either barley silage or barley straw. Applying the enzyme mixture onto the barley lowered the concentrations of dietary ADF and NDF. However, it is not certain when this fiber hydrolysis occurred relative to feed consumption because the fiber analyses were conducted after the study was completed. Enzyme treatment of barley increased total tract dietary ADF digestibility by 28% (P < .05). Acetate-to-propionate ratio tended to decrease, which suggests that enzymes may have increased ruminal starch digestion as a result of enhanced digestion of barley hulls. Replacing silage with straw increased ADF intake (P < .05) and resulted in 1-h/d increase in rumination time (P < .05). Even though there was no effect of diet on ruminal pH, replacing silage with straw increased ruminal acetate, as a percentage of total VFA, and total tract ADF digestion (P < .01). This study demonstrates that using a fibrolytic enzyme mixture in high-grain diets that contain mainly barley grain can improve fiber digestion and grain utilization, but the mode of action is unclear. Straw can be used rather than silage to increase the effective fiber content of a high-grain feedlot diet. Key Words: Beef Cattle, Barley, Enzymes, Fiber, Digestion

A study was conducted to evaluate the effects of mastication on the physical breakdown and ruminal digestion of whole cereal grains by cattle. Three Hereford cows (initial BW 557 kg; SD, 17) surgically fitted with ruminal and esophageal fistulas were fed 5.5 kg/d (as-fed basis) of whole barley, corn, or wheat in an experiment designed as a 3 x 3 Latin square. Eating time and chews per kilogram of DM were greater (P |is less than~ .10) for corn than for barley or wheat. Whole corn was substantially damaged after ingestive mastication, and the majority of kernels were broken into small pieces. Many barley and wheat kernels showed signs of dentition, but most kernels remained intact. Less saliva (P |is less than~ .10) was added to whole wheat than to barley or corn during ingestive mastication. Cattle fed whole barley spent twice (P |is less than~ .10) as long ruminating per kilogram of DM as those fed corn, with intermediate times for wheat. Less than 30% of the DM disappeared from unmasticated whole grains during 96 h of ruminal incubation. Ingestive mastication increased DM digestion to 53, 69, and 66% for barley, corn, and wheat, respectively. Mastication alters the kinetics of ruminal digestion of unprocessed cereal grains. Combined with the inherent protein and starch digestibilities of the grain, mastication affects the type and extent of processing required to optimize the utilization of cereal grains by cattle. Unlike barley and wheat, corn kernels are extensively damaged during ingestive mastication, reducing the need for physical processing.