Feedlot Cattle Diets Research Articles

Greenhouse gas emissions when composting manure from cattle fed wheat dried distillers’ grains with solubles

Dried distillers’ grains with solubles (DDGS) are a co-product of ethanol production that is increasingly available for use as a livestock feed. Including DDGS in diets could affect animal manure properties and impact manure management strategies. The objectives of this study were to investigate changes in the rate of greenhouse gas (GHG) emissions during composting and final properties of manure compost when DDGS is included in feedlot cattle diets. Treatments were: (1) Control; manure from cattle fed a typical finishing diet containing barley (Hordeumvulgare L.) grain and silage and (2) DDGS; manure from cattle fed a finishing diet with 60% DDGS from wheat (Triticumaestivum L.) in the dietary ration. Manure, consisting of feces, urine and wood shavings, was composted in open windrows. Samples were collected for analysis at initiation and completion of composting. Greenhouse gas surface fluxes were collected weekly during the first 4 weeks and every 2–3 weeks for the remainder of the composting period. The DDGS compost had lower total C, but similar total N (TN) content relative to Control, reflecting the initial manure conditions. The DDGS compost also had higher moisture, higher water-extractable NH4+ and NO3−, a greater fraction of TN in available form, and a lower pH than the Control. The O2 consumption and N2O emission from DDGS compost were higher, whereas CO2 and CH4 emissions were similar to Control. The higher N2O emissions from DDGS compost were likely related to the high water-extractable N content in DDGS manure. Increased use of DDGS in feedlot diets may have environmental repercussions that include greater emissions of GHG (N2O) during manure composting. From an end user perspective, enhanced availability of N could increase the nutrient value of the compost for crop production.

Effects of Dried Distillers' Grains with Solubles (Wheat‐Based) in Feedlot Cattle Diets on Feces and Manure Composition

Effects of Dried Distillers' Grains with Solubles (Wheat‐Based) in Feedlot Cattle Diets on Feces and Manure Composition

Cinnamaldehyde in feedlot cattle diets: Intake, growth performance, carcass characteristics, and blood metabolites1

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 animals. 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 +/- 25.2 kg) were assigned to a randomized complete block design with 5 treatments: control (no additive), monensin (MO; 330 mg*steer(-1)*d(-1)), and 400, 800, or 1,600 mg of CIN*steer(-1)*d(-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.

Effects of Dried Distillers' Grains with Solubles (Wheat‐Based) in Feedlot Cattle Diets on Feces and Manure Composition

The use of dried distillers' grains with solubles (DDGS) in feedlot cattle (Bos taurus) diets is increasing as the bio-ethanol industry expands. This study investigated how wheat (Triticum aestivum L.) DDGS-based diets impact feedlot cattle nutrient and volatile fatty acid (VFA) excretion. Feedlot heifers were fed DDGS at 0 (Control) 20, 40, 60% or 60% + Ca (1% limestone) of dietary dry matter. Feces and manure were sampled monthly over a 133-d finishing period. Total nitrogen (TN) (feces only), total phosphorus (TP), pH (manure only), and water soluble NH(4)(+) and P contents in feces and manure were higher with 40 and 60% DDGS diets than with the Control. Significant increases in isobutyric, valeric, and isovaleric VFAs (by far the most odorous in manure) were also observed in the feces with 40 and 60% DDGS diets, although there was no change in the total VFA content with diet. Wheat DDGS manure, with higher N and P contents, should be beneficial to crop production. However, it could potentially increase N and P loading on crop lands after application and contribute to greater NH(3) emission and malodor intensity while manure is in the feedlot pen. Estimated manure N loss while in feedlot pens also increased significantly with dietary DDGS levels. The small (nonsignificant) differences in total and soluble N and P in feces and manure between 20% DDGS and the Control (0% wheat DDGS) suggest that excess nutrient flow to the environment and malodors can be controlled by restricting wheat DDGS to a maximum of 20% in cattle diets.

Impact of a mixed culture of Lactobacillus casei and L. lactis on in vitro ruminal fermentation and the growth of feedlot steers fed barley-based diets

The effect of a direct-fed microbial (DFM) poduct containing a mixed culture of Lactobacillus casei and L. lactis on in vitro ruminal fermentation of barley-grain/barley-silage-based backgrounding and finishing diets and on growth performance and carcass characteristics of feedlot cattle was evaluated during backgrounding (84 d) and finishing (140 d) of 100 Hereford × Angus steers (initial body weight = 280 ± 15.5 kg). The inclusion rates of DFM in the in vitro study were 4, 8, 12 and 16 million colony forming units (CFU) of lactic acid bacteria (LAB) kg-1 DM of substrate. Total in vitro volatile fatty acids (VFA) production increased at 6 and 12 h of incubation (P < 0.01; linear response) when the backgrounding diet was supplemented with DFM. Dry matter digestibility and VFA production also increased (P < 0.05) during a 12-h fermentation of the finishing diet. Steers were randomly allocated to one of four dietary treatments that comprised feeding DFM tp provide 0 (control), 4 × 107, 8 × 107, or 12 × 107 CFU kg-1 diet DM. Average daily gain (ADG, kg) and feed efficiency (G:F; kg gain kg-1 DM consumed) of steers improved (P = 0.002 and 0.001, respectively) as a result of feeding DFM during the backgrounding period, but not during the finishing period. Saleable meat and rib eye area decreased (P = 0.038, linear; and P = 0.041, quadratic) with DFM supplementation. The results indicated that supplementing barley-grain/barley-silage-based feedlot cattle diets with 12 × 107 CFU of the mixed culture of lactobacilli used in these studies could improve ruminal fermentation, ADG and G:F in backgrounding feedlot steers. However, supplementation during the finishing period may not be warranted in terms of growth performance and carcass characteristics. Differences in the microbial ecology of the intestinal tract as a result of differences in diet composition may account for the varied response between the backgrounding and finishing periods.Key words: Beef cattle, direct-fed microbial, growth performance, Lactobacillus casei, Lactobacillus lactis, ruminal fermentation

Citrus Products Decrease Growth of E. coli O157:H7 and Salmonella Typhimurium in Pure Culture and in Fermentation with Mixed Ruminal Microorganisms In Vitro

Orange peel and orange pulp are by-products that are included in feedlot and dairy cattle diets because of their low cost and high nutritional quality. The antimicrobial activity of citrus oils has been reported previously. The present study was carried out to determine whether these citrus by-products exert antimicrobial effects on Escherichia coli O157:H7 and Salmonella Typhimurium populations that are found in cattle gastrointestinal tracts. The growth of pure cultures (n = 3) of E. coli O157:H7 and Salmonella Typhimurium were reduced (p < 0.05) by addition of 2% (w/v) orange pulp and orange peel. Ruminal fluid was collected from cattle (n = 2) and E. coli O157:H7 or Salmonella Typhimurium were added. The addition of orange pulp and peel to in vitro mixed ruminal microorganism fermentations (n = 3) demonstrated that both orange pulp and peel reduced E. coli O157:H7 and Salmonella Typhimurium populations at least 2 log(10) in mixed ruminal fluid fermentations. Addition of orange pulp reduced (p < 0.05) E. coli O157:H7 populations from 10(5) to 10(2) colony-forming units (CFU)/mL and Salmonella Typhimurium populations (p < 0.05) from 10(4) to 10(2) CFU/mL. These results indicate that orange pulp and/or peel included in ruminant diets could decrease ruminal populations of foodborne pathogenic bacteria. Further research is needed to determine whether the antimicrobial activity of orange products against E. coli O157:H7 or Salmonella Typhimurium is expressed in the lower gastrointestinal tract.

CASE STUDY: Supplementation of Chelated Forms of Zinc, Copper, and Manganese to Feedlot Cattle with Access to Drinking Water with High Sulfate Concentration

<h2>ABSTRACT</h2> The objective of this experiment was to evaluate the effects of supplementing a blend of chelated Zn-(2-hydroxy-4-methylthio butanoic acid; HMTBA)₂, Cu-(HMTBA)₂, and Mn-(HMTBA)₂ to feedlot cattle with access to drinking well water that contains high levels of sulfate (1,646 mg/kg). A total of 640 weaned calves with an average BW of 192 ± 12kg were allocated to 4 pens per treatment in a randomized complete block design and fed a control diet or a diet supplemented with 37, 17.5, and 15.2 mg/kg of Zn from Zn-(HMTBA)₂, Cu from Cu-(HMTBA)₂, and Mn from Mn-(HMTBA)₂, respectively, for the entire feedlot period (267 d). Average daily gain, feed intake and gain to feed ratio were not affected by treatment. However, cattle fed Zn-(HMTBA)₂, Cu-(HMTBA)₂, and Mn-(HMTBA)₂ exhibited less mortality (4.7 vs. 2.44%; P=0.05) and morbidity (47.1 vs. 37.8%; P=0.06). Carcass quality was improved by reducing the dark-cutting carcasses from 3.59 to 0.77% (P = 0.02) and fat deposition from kidney, pelvic, and heart area (P = 0.05). From this study, we concluded that supplementation of Zn-(HMTBA)₂, Cu-(HMTBA)₂, and Mn-(HMTBA)₂ to feedlot cattle with access to water with high sulfate concentration improved health and carcass quality. The net economic improvement of adding Zn-(HMTBA)₂, C-(HMTBA)₂, and Mn-(HMTBA)₂ to feedlot cattle diets represented $17.96 per head savings in cattle health and carcass performance when compared with controls.

Barley- versus protein-supplemented corn-based diets for feedlot cattle evaluated using the NRC and CNCPS beef models

A study was conducted to evaluate the effects of supplementing a corn-based finishing diet [10.0% crude protein (CP), 6.2% degradable intake protein (DIP), dry matter basis, no protein supplementation] with DIP in the form of urea (13.0% CP, 9.1% DIP) or canola meal and urea (12.8% CP, 8.6% DIP) on dry matter intake (DMI) and average daily gain (ADG). Animal performances were compared with those obtained by feeding a barley-based diet (13.9% CP, 9.6% DIP). Crossbred beef steers (398 ± 28 kg) were allocated to 24 pens and six pens were assigned to each diet. There were no differences (P &gt; 0.05) in DMI and ADG between cattle fed the barley diet and those fed the corn diets supplemented to provide a concentration of DIP similar to that supplied by the barley diet. However, ADG was 10% lower and DMI was 8% lower for cattle fed the corn diet with no protein supplementation (P &lt; 0.05). The NRC and CNCPS models predicted the substantially lower gain of cattle fed the corn diet with no protein supplementation, but underestimated the improvement in performance when the corn diet was supplemented with urea or canola meal and urea to supply the requirement for DIP. Key words: Feedlot cattle, protein, corn, barley, growth, models

Feedlot cattle diets based on barley or corn supplemented with dry corn gluten feed evaluated using the NRC and CNCPS beef models

A study was conducted to evaluate the effects of supplementing feedlot finishing corn diets with dry corn gluten feed (CGF). Animal performance and carcass traits were compared with those obtained by feeding a barley-based diet typical of diets fed commercially in western Canadian feedlots. The second objective of the experiment was to evaluate the diets using the 1996 National Research Council (NRC) Beef (level 1 and 2) and Cornell Net Carbohydrate and Protein System (CNCPS, version 5.0) models to determine how well the models predict animal response. Crossbred beef steers (248) weighing 423 ± 20.5 kg were allocated to 24 pens and then six pens were assigned to each of four diets: (1) barley grain (13.8% crude protein, CP), (2) corn grain (9.2% CP), (3) corn grain supplemented with a low level (7%, DM basis) of CGF (CGF-low, 9.7% CP), and (4) corn grain supplemented with a high level (23%) of CGF (CGF-high, 11.7% CP). The barley grain was steam-rolled and the corn grain was dry-rolled. All diets contained 8% barley silage (DM basis). The cattle were adapted from a backgrounding diet to the experimental diets over a period of 28 d and then fed for a period of 136 d. During the adaptation phase cattle fed unsupplemented corn grew slower (P &lt; 0.05) than the cattle fed the other diets (1.23 vs. 1.52 kg d-1). However, after day 42 of the study, cattle fed unsupplemented corn grew very rapidly such that gain for the entire feeding period was similar for cattle fed unsupplemented corn and barley diets (1.62 vs. 1.58, P &gt; 0.05). Furthermore, growth rate was higher (P &lt; 0.05) for cattle fed barley or unsupplemented corn than for cattle fed low or high levels of CGF (1.48 and 1.45 kg d-1, respectively). The dry matter intake (DMI) averaged 11.4 kg d-1 during the feeding period and was not affected (P &gt; 0.05) by diet. Feed:gain ratio (kg DM:kg gain) was similar (P &gt; 0.05) for cattle fed barley (7.09) and unsupplemented corn (7.38), but was higher (P &lt; 0.05) for cattle fed CGF-high (7.92), and intermediate (P &gt; 0.05) for those fed CGF-low (7.52). There were no differences in carcass composition between barley and corn-fed cattle, but those fed low and high levels of CGF had carcasses that were fatter with lower lean meat yield. The three models underestimated DMI of all four diets. When DMI was set to observed intake in the models, CNCPS accurately predicted ADG and F:G ratio for cattle fed corn diets, but all models underestimated ADG of cattle fed barley. All models correctly predicted that gain during the feeding period was not limited by protein supply. The results from this study indicate that rolled-corn diets containing about 9.5% CP, with 50% of the CP as DIP are adequate for feedlot cattle weighing more that 500 kg. Substituting dry CGF for corn grain reduces feed efficiency and gain due to the lower digestible energy content of CGF. Key words: Grain, barley, corn, corn gluten feed, feedlot cattle, protein, models

Effect of pelletizing on the feeding value of rice straw in steam-flaked corn growing-finishing diets for feedlot cattle

Trial 1. Three cannulated crossbred steers were used to compare the effects of ground versus pelletized rice straw on characteristics of digestion. Treatments consisted of a steam-flaked corn-based diet containing 120 g/kg sudangrass (SG, positive control), ground rice straw (GRS) or pelletized rice straw (PRS). Ruminal digestion of organic matter was similar across treatments ( P<0.10). Ruminal digestion of neutral detergent fiber was low, averaging 140 g/kg, and not affected ( P>0.10) by forage source. Ruminal starch digestion was lower (5%; P<0.05) for sudangrass than for rice straw diets, and greater (8%, P<0.01) for pelletized versus ground straw. Ruminal microbial efficiency was greater (9.7%; P<0.05) for ground than for pelletized rice straw. Total tract digestion of dry matter was greater (3%, P<0.10) for sudangrass than for rice straw treatments and NDF digestion was lower (26%; P<0.05) for rice straw than for sudangrass diets. Total tract starch digestion was greater (2%, P<0.01) for pelletized than for ground rice straw diets, due largely to greater ruminal starch digestion. Treatment effects were numerically similar for ground sudangrass and ground rice straw diets. Pelletized rice straw increased ( P<0.05) ruminal total volatile fatty acid (VFA) and propionate concentrations by 24 and 47% respectively, and decreased ruminal pH (9%, P<0.05), ruminal acetate:propionate molar ratio (27%, P<0.05), and estimated methane production (28%, P<0.05). Trial 2. Ninety crossbred yearling steers were used in a 112 day finishing trial to evaluate the influence of pelletizing on the feeding value of rice straw. Treatments were the same as Trial 1. Substituting ground rice straw for sudangrass had no detrimental effects ( P>0.10) on energy intake or average daily gain (ADG). However, DMI and ADG were greater (11%, P<0.05, and 12%, P<0.10, respectively) for ground than for pelletized rice straw supplemented diets. There were no treatment effects ( P>0.10) on dressing percentage, which had a carcass to live weight ratio averaging 0.642. Steers fed the sudangrass diet had a lower yield grade (16%; P<0.01), marbling score (13%; P<0.05), and fat thickness (15%; P<0.10) than those fed the rice straw diets. Feeding pelletized straw reduced marbling score (10%, P<0.10), and fat thickness (20%; P<0.10) when compared with ground rice straw. As expected, NE m and NE g were greater (5%; P<0.01) for sudangrass than for rice straw diets. Pelletizing rice straw did not decrease ( P=0.56) the dietary net energy (NE) value of the rice straw supplemented diets. Thus, the difference in ADG due to feeding ground versus pelletized rice straw is attributable solely to treatment effects on DMI. We conclude that at lower levels of rice straw inclusion (<150 g/kg) fed to steers in growing-finishing diets, pelletizing the straw may reduce intake and gain through a satiety response mechanism, possibly associated with increased propionate production.

Effects of stage of maturity and protein supplementation on growth and nitrogen utilisation by cattle fed oat silage

Cereal silages are used extensively in the diets of feedlot cattle all over western Canada. Plants are generally harvested at dough stage as this stage is believed to represent the best compromise between feeding value and dry matter yield. However, under the growing conditions of eastern Canada, where cereals are grown as cover crops, it has been argued that harvesting at the boot stage would be beneficial to the establishment of the under sown crop and could improve yields of digestible dry matter. Previous experiments have suggested that cereal silages harvested at boot stage vs soft dough stage (Acosta et al., 1991), although the former were more digestible, resulted in no benefit in terms of animal performance. Our work with grass silages (Berthiaume et al, 1996) showed that this could be due to the highly degradable nature of protein in immature silages, and that protein supplements would be beneficial. This study evaluated the effect of harvesting oats for silage at boot vs milk stage with or without the addition of a protein supplement on nitrogen utilisation and growth of calves.

Value of sunflower seed in finishing diets of feedlot cattle.

The value of sunflower seed (SS) in finishing diets was assessed in two feeding trials. In Exp. 1, 60 yearling steers (479 +/- 45 kg) were fed five diets (n = 12). A basal diet (DM basis) of 84.5% steam-rolled barley, 9% barley silage, and 6.5% supplement was fed as is (control), with all the silage replaced (DM basis) with rolled SS, or with grain:silage mix replaced with 9% whole SS, 14% whole SS, or 14% rolled SS. Liver, diaphragm, and brisket samples were obtained from each carcass. In Exp. 2, 120 yearling steers (354 +/- 25 kg) were fed corn- or barley-based diets containing no SS, high-linoleic acid SS, or high-oleic acid SS (a 2 x 3 factorial arrangement, n = 20). Whole SS was included at 10.8% in the corn-based and 14% in the barley-based diets (DM basis). In Exp. 1, feeding whole SS linearly increased DMI (P = 0.02), ADG (P = 0.01), and G:F (P = 0.01). Regression of ME against level of whole SS indicated that SS contained 4.4 to 5.9 Mcal ME/kg. Substituting whole for rolled SS did not significantly alter DMI, ADG, or G:F (8.55 vs. 8.30 kg/d; 1.36 vs. 1.31 kg; and 0.157 vs. 0.158, respectively). Replacing the silage with rolled SS had no effect on DMI (P = 0.91) but marginally enhanced ADG (P = 0.10) and improved G:F (P = 0.01). Dressing percent increased linearly (P = 0.08) with level of SS in the diet. Feeding SS decreased (P < 0.05) levels of 16:0 and 18:3 in both diaphragm and subcutaneous fats, and increased (P = 0.05) the prevalence of 18:1, 18:2, cis-9,trans-11-CLA and trans-10,cis-12-CLA in subcutaneous fat. In Exp. 2, barley diets supplemented with high-linoleic SS decreased DMI (P = 0.02) and ADG (P = 0.007) by steers throughout the trial, whereas no decrease was noted with corn (interaction P = 0.06 for DMI and P = 0.01 for ADG). With barley, high-linoleic SS decreased final live weight (554 vs. 592 kg; P = 0.01), carcass weight (329 vs. 346 kg; P = 0.06), and dressing percent (58.5 vs. 59.4%; P = 0.04). Steers fed high-linoleic SS plus barley had less (P < 0.05) backfat than those fed other SS diets. No adverse effects of SS on liver abscess incidence or meat quality were detected. Although they provide protein and fiber useful in formulating finishing diets for cattle, and did improve performance in Exp. 1, no benefit from substituting SS for grain and roughage was detected in Exp. 2. Because of unexplained inconsistencies between the two experiments, additional research is warranted to confirm the feeding value of SS in diets for feedlot cattle.

Ascophyllum nodosumSupplementation: A Preharvest Intervention for Reducing Escherichia coli O157:H7 and Salmonella spp. in Feedlot Steers

Ascophyllum nodosum (Tasco-14) decreased the prevalence of enterohemorrhagic Escherichia coli (EHEC) O157:H7 in animals fed prior to harvest. Tasco-14 was supplemented on a 2% dry matter basis 14 days prior to harvest to determine its effects on EHEC and Salmonella spp. prevalence. Two hundred mixed crossbred steers and heifers (Bos indicus × Bos taurus), in a large commercial finishing facility, served as experimental units. Treatment (TRT, n = 100) animals received a steam-rolled corn-based diet containing 2% Tasco-14 on a dry matter basis, and control (CON, n = 100) animals received only the steam-rolled corn-based diet. Hide swabs and fecal samples were obtained for EHEC and Salmonella spp. evaluations. Animals were sampled 1 day prior to (d − 1) the feeding of Tasco-14 and immediately following exsanguinations. The prevalence of EHEC O157 on hide swabs and in fecal samples (P = 0.0001 and P < 0.0001, respectively) and the prevalence of EHEC O157:H7 on hide swabs and in fecal samples (P < 0.0001 and P < 0.0001, respectively) was reduced by 33 and 36% from d − 1 levels on TRT hide swabs and by 9 and 11% in TRT fecal samples. The prevalence of EHEC O157 and EHEC O157: H7 was reduced by 33 and 36% from d − 1 levels on TRT hide swabs and by 9 and 11% in TRT fecal samples. The prevalence of Salmonella spp. on hide swabs did not change for TRT animals (P = 0.64). CON animals showed an increase in Salmonella spp. prevalence (P < 0.0001) from d − 1 feeding levels on hide swabs. The prevalence of Salmonella spp. increased in both TRT and CON fecal samples when compared to d − 1 levels (P = 0.002). However, TRT samples exhibited a lower (P < 0.05) postfeeding prevalence of Salmonella spp. in fecal samples than did CON samples. Results from this study indicate that 2% Tasco-14 supplementation in feedlot cattle diets reduces EHEC O157 and EHEC O157:H7 prevalence on hide swabs and in fecal samples and may suppress increases in Salmonella spp.

In vitro effects of Monensin and Tween 80 on ruminal fermentation of barley grain:barley silage-based diets for beef cattle

Two in vitro incubations utilizing batch rumen culture procedures were conducted to study the effects of Monensin and Tween 80, alone and in combination, on ruminal fermentation. Dried, ground backgrounding and finishing diets for feedlot cattle were used as substrates in experiments 1 and 2, respectively. The diets, formulated as total mixed rations, contained (DM basis) barley grain and barley silage in ratios of 58:42 (backgrounding diet, BKGD) or 93:7 (finishing diet, FNSH). Inoculum comprised ruminal fluid collected from cattle fed BKGD or FNSH diluted with two volumes of mineral buffer, and amended with Monensin (0, 2.5 or 15 μg/ml) and Tween 80 (0, 0.1 or 0.5 μl/ml) in a 3 × 3 factorial arrangement of treatments. Incubations were conducted anaerobically for 4, 12 or 24 h at 39 °C ( n = 3). 15N-labelled ammonium sulphate was included to enable measurement of microbial N production (MN). Interactive effects ( P < 0.001) of Monensin and Tween 80 on acetate:propionate (A:P) ratios at 4 and 12 h of incubation, on MN at 4 and 24 h, and on accumulation of reducing sugars (RS) at 4, 12 and 24 h were observed with BKGD, but not with FNSH. Tween 80 applied at 0.5 μl/ml increased ( P < 0.05) in vitro true dry matter disappearance (TDMD) and RS accumulation at 4 h and MN at 24 h, but reduced ( P < 0.05) A:P ratio at 12 h of incubation with BKGD. Similar effects of Tween 80 on RS and A:P ratio were observed with FNSH. In contrast, throughout 24 h of incubation with either substrate, Monensin reduced gas production (GP), TDMD, MN and the A:P ratio, and increased RS accumulation (BKGD, P < 0.01; FNSH, P < 0.001). These effects on A:P and RS were enhanced ( P < 0.001) if Monensin and Tween 80 were supplemented together. Amylase, carboxymethylcellulase and β-glucanase activities in the incubation liquid were increased ( P < 0.01) by Monensin and Tween 80 supplemented in combination with both diets; xylanase activity was increased ( P < 0.001) with BKGD only. Effects on enzyme activity when Monensin and Tween 80 were supplemented individually were diet-associated, but interactive effects of Monensin × Tween 80 on each of the four activities were observed both with BKGD ( P < 0.05–0.001) and with FNSH ( P < 0.01). Supplementing Tween 80 with Monensin synergistically enhanced the Monensin-mediated increase in RS concentration and reduction of A:P ratio in the incubation mixtures. This effect may have potential to improve energy efficiency in feedlot cattle.

A rationale for the development of feed enzyme products for ruminants

The use of exogenous cell wall degrading enzymes is an emerging technology that shows potential in terms of improving feed utilization by ruminants. This review discusses current information related to enzyme product formulation for ruminants, and addresses the conditions necessary to ensure effective and consistent in vivo results of providing feed enzymes to ruminants. Research has demonstrated that, in some cases, adding fibrolytic enzymes to dairy cow and feedlot cattle diets improves cell wall digestion and, consequently, weight gain or milk production are enhanced. However, considerable research is required to develop more effective enzyme products and to ensure consistency of responses in vivo. There is a need to identify the key enzyme activities involved in the positive responses observed in vivo and these enzyme activities should be assessed using a temperature and pH representative of the conditions in the rumen. However, to date, it has not been possible to accurately evaluate exogenous enzymes based only on their biochemical characterization because the model substrates used do not represent the complexity of plant cell wall material. In vitro techniques using feed substrates, buffer and ruminal fluid can be used more reliably as a bioassay to predict in vivo response to exogenous enzymes, however, other factors, including under or over-supplementation of enzyme activity, method of providing the enzyme product to the animal, composition of the diet, and the target animals must also be considered. Key words: Cattle, digestion, fibre digestion, enzymes, cellulases, hemicellulases

Effects of bacterial direct-fed microbials and yeast on site and extent of digestion, blood chemistry, and subclinical ruminal acidosis in feedlot cattle.

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(9) cfu/d). In Exp. 2, treatments were control vs EF (6 x 10(9) cfu/d) and yeast (Saccharomyces cerevisiae; 6 x 10(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.

Effects of supplemental protein removal on total and acid-resistant E. coli, total coliforms, and performance in finishing steers (2003)

Fifty-four crossbred finishing steers were used to measure the effects of reducing supplemental protein (nitrogen) on feedlot performance and fecal shedding of acidresistant Escherichia coli and total coliform bacteria. A control diet (15.0% crude protein; high protein) was compared to a low protein diet (8.9% crude protein; low protein) from which supplemental nitrogen sources (urea and soybean meal) were removed for the last 8 days of the feeding period. Fecal E. coli and coliform populations were measured prior to harvest. Removal of supplemental nitrogen from feedlot cattle diets did not substantially reduce populations of acid-resistant fecal E. coli and coliforms. Fecal pH tended to be lower (P=0.11) and the molar percentage of fecal isobutyrate and valerate were lower (P<0.05) for steers receiving low protein diets, but total fecal volatile fatty acid concentrations were not affected by dietary treatment. Dry matter intake tended to be lower (P<0.10) for steers fed low protein diets, whereas daily gains, feed:gain, final weights, dressing percentages, and carcass characteristics were similar for cattle fed low and high protein diets.

Performance of growing and finishing cattle supplemented with a slow-rlease urea product and urea

Two growth trials were conducted to study the performance of Angus Crossbred steers supplemented with a slow-release urea product (Optigen® 1200, O) and urea (U). The base diets were composed of corn silage alone during the growth period and corn silage plus cracked corn during the finishing period. Trial 1 consisted of 40 animals [272 ± 4 kg body weight (BW)] individually fed the base diets and six treatments, which were based on corn silage alone and cracked corn supplemented with U or O to supply 50 (U50, O50) or 100% (U100, O100) of the ruminal N deficiency (U50, O50, U100, and O100) as predicted by the Cornell Net Carbohydrate and Protein System (CNCPS), or with U and O each supplying half of the CNCPS predicted N deficiency (U25O25). In trial 2, 120 pen-fed animals (241 ± 7 kg BW) received the base diets and four combinations of U and O ( U100O0, U66O34, U34O66, and U0O100), which were designed to supply 100% of the ruminal N deficiency predicted by the CNCPS. In trial 1, no differences (P &gt; 0.05) in performance were observed between the U100 and O100 treatments, but animals in the U50 treatment had a greater average daily gain (ADG) (P &lt; 0.05) and feed conversion (P &lt; 0.05) than animals on O50 treatment. In trial 2, combinations of U and O did not affect animal performance (P &gt; 0.05). No differences were observed in carcass characteristics and predicted carcass and empty body fat for both trials (P &gt; 0.05). We concluded there was no improvement in animal performance when urea was substituted by a slow-release urea/NH3 product at levels normally found in feedlot cattle diets. Key words: Cornell net carbohydrate and protein system, modeling, nutrition, growth, non-protein nitrogen

Evaluation of a Forage-Fat Blend as an Isocaloric Substitute for Steam-Flaked Wheat in Finishing Diets for Feedlot Cattle: Growth Performance and Digestive Function

Two trials were conducted to evaluate the addition of a forage-fat blend (FFB) as a substitute for grain in finishing diets for feedlot cattle. Treatments consisted of a steam-flaked wheat-based finishing diet containing 15, 29, or 45% FFB. The FFB contained 80% chopped alfalfa hay and 20% yellow grease and was formulated to have NEm and NEg values similar to that of wheat. In Trial 1, 126 crossbred steers (225 ± 5.4 kg) were used to evaluate treatment effects on growth performance and dietary NE. In Trial 2, three Holstein steers (448 ± 21 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on characteristics of digestion. Increasing the FFB did not affect (P>0.10) ADG, but decreased gain efficiency (linear effect, P<0.05) and dietary NE concentration (linear effect, P<0.01). Increasing the FFB did not affect (P>0.10) ruminal digestion of starch, N, or microbial N (MN) efficiency, but decreased (linear effect, P<0.10) ruminal digestion of OM and increased (linear effect, P<0.10) ruminal digestion of ADF. Increasing the FFB did not affect (P>0.10) postruminal digestion of OM, starch, and N, but decreased postruminal digestion of fatty acids (linear effect, P<0.05). Increasing the FFB did not affect (P>0.10) percentage of total tract starch, N, and ADF digestion, but decreased the percentage of total tract digestion of OM (linear effect, P<0.01) and DE (linear effect, P<0.05). We conclude that an isocaloric FFB can replace grain at levels of up to 45% of dietary DM without affecting ADG in feedlot cattle. However, when dietary inclusion rates are > 15%, dietary NE and, hence, BW gain efficiency may decrease. The magnitude of the effect of FFB inclusion rate on energy recovery is a predictable function of the relationship between fatty acid intake and intestinal fatty acid digestion.

Phosphorus requirement of finishing feedlot calves.

Dietary P supplied to feedlot cattle is important because an inadequate supply will compromise performance, whereas excess P may harm the environment. However, P requirements of feedlot cattle are not well documented. Therefore, 45 steer calves (265.2+/-16.6 kg) were individually fed to determine the P required for gain and bone integrity over a 204-d finishing period. The basal diet consisted of 33.5% high-moisture corn, 30% brewers grits, 20% corn bran, 7.5% cottonseed hulls, 3% tallow, and 6% supplement. Treatments consisted of 0.16 (no supplemental inorganic P), 0.22, 0.28, 0.34, and 0.40% P (DM basis). Supplemental P was provided by monosodium phosphate top-dressed to the daily feed allotment. Blood was sampled every 56 d to assess P status. At slaughter, phalanx and metacarpal bones were collected from the front leg to determine bone ash and assess P resorption from bone. Dry matter intake and ADG did not change linearly (P > 0.86) or quadratically (P > 0.28) due to P treatment. Feed efficiency was not influenced (P > 0.30) by P treatment and averaged 0.169. Plasma inorganic P averaged across d 56 to 204 responded quadratically, with calves fed 0.16% P having the lowest concentration of plasma inorganic P. However, plasma inorganic P concentration (5.7 mg/dL) for steers fed 0.16% P is generally considered adequate. Total bone ash weight was not influenced by dietary P for phalanx (P = 0.19) or metacarpal bones (P = 0.37). Total P intake ranged from 14.2 to 35.5 g/d. The NRC (1996) recommendation for these calves was 18.7 g/d, assuming 68% absorption. Based on performance results, P requirements for finishing calves is < 0.16% of diet DM or 14.2 g/d. Based on these observations, we suggest that typical grain-based feedlot cattle diets do not require supplementation of inorganic mineral P to meet P requirements.