Showing papers by "Tim A. McAllister published in 2013"

Characterization of the core rumen microbiome in cattle during transition from forage to concentrate as well as during and after an acidotic challenge.

Abstract: This study investigated the effect of diet and host on the rumen bacterial microbiome and the impact of an acidotic challenge on its composition. Using parallel pyrosequencing of the V3 hypervariable region of 16S rRNA gene, solid and liquid associated bacterial communities of 8 heifers were profiled. Heifers were exclusively fed forage, before being transitioned to a concentrate diet, subjected to an acidotic challenge and allowed to recover. Samples of rumen digesta were collected when heifers were fed forage, mixed forage, high grain, during challenge (4 h and 12 h) and recovery. A total of 560,994 high-quality bacterial sequences were obtained from the solid and liquid digesta. Using cluster analysis, prominent bacterial populations differed (P≤0.10) in solid and liquid fractions between forage and grain diets. Differences among hosts and diets were not revealed by DGGE, but real time qPCR showed that several bacteria taxon were impacted by changes in diet, with the exception of Streptococcus bovis. Analysis of the core rumen microbiome identified 32 OTU's representing 10 distinct bacterial taxa including Bacteroidetes (32.8%), Firmicutes (43.2%) and Proteobacteria (14.3%). Diversity of OTUs was highest with forage with 38 unique OTUs identified as compared to only 11 with the high grain diet. Comparison of the microbial profiles of clincial vs. subclinical acidotic heifers found a increases in the relative abundances of Acetitomaculum, Lactobacillus, Prevotella, and Streptococcus. Increases in Streptococcus and Lactobacillus likely reflect the tolerance of these species to low pH and their ability to proliferate on surplus fermentable carbohydrate. The acetogen, Acetitomaculum may thereforeplay a role in the conversion of lactate to acetate in acidotic animals. Further profiling of the bacterial populations associated with subclinical and clinical acidosis could establish a microbial fingerprint for these disorders and provide insight into whether there are causative microbial populations that could potentially be therapeutically manipulated.

Changes in the Rumen Epimural Bacterial Diversity of Beef Cattle as Affected by Diet and Induced Ruminal Acidosis

Abstract: Little is known about the nature of the rumen epithelial adherent (epimural) microbiome in cattle fed different diets. Using denaturing gradient gel electrophoresis (DGGE), quantitative real-time PCR (qPCR), and pyrosequencing of the V3 hypervariable coding region of 16S rRNA, epimural bacterial communities of 8 cattle were profiled during the transition from a forage to a high-concentrate diet, during acidosis, and after recovery. A total of 153,621 high-quality gene sequences were obtained, with populations exhibiting less taxonomic variability among individuals than across diets. The bacterial community composition exhibited clustering (P 1% of the rumen epimural population, differing (P ≤ 0.05) among diets. During acidosis, levels of Atopobium, Desulfocurvus, Fervidicola, Lactobacillus, and Olsenella increased, while during the recovery, Desulfocurvus, Lactobacillus, and Olsenella reverted to levels similar to those with the high-grain diet and Sharpea and Succinivibrio reverted to levels similar to those with the forage diet. The relative abundances of bacterial populations changed during diet transition for all qPCR targets except Streptococcus spp. Less than 5% of total operational taxonomic units (OTUs) identified exhibited significant variability across diets. Based on DGGE, the community structures of epithelial populations differed (P ≤ 0.10); segregation was most prominent for the mixed forage diet versus the grain, acidotic challenge, and recovery diets. Atopobium, cc142, Lactobacillus, Olsenella, RC39, Sharpea, Solobacterium, Succiniclasticum, and Syntrophococcus were particularly prevalent during acidosis. Determining the metabolic roles of these key genera in the rumens of cattle fed high-grain diets could define a clinical microbial profile associated with ruminal acidosis.

Effect of subtherapeutic vs. therapeutic administration of macrolides on antimicrobial resistance in Mannheimia haemolytica and enterococci isolated from beef cattle

Abstract: Macrolides are the first-line treatment against bovine respiratory disease, and are also used to treat infections in humans. The macrolide, tylosin phosphate, is often included in the diet of cattle as a preventative for liver abscesses in many regions of the world outside of Europe. This study investigated the effects of administering macrolides to beef cattle either systemically through a single subcutaneous injection (therapeutic) or continuously in-feed (subtherapeutic), on the prevalence and antimicrobial resistance of Mannheimia haemolytica and Enterococcus spp. isolated from the nasopharynx and faeces, respectively. Nasopharyngeal and faecal samples were collected weekly over 28 days from untreated beef steers and from steers injected once with tilmicosin or tulathromycin or continuously fed tylosin phosphate at dosages recommended by manufacturers. Tilmicosin and tulathromycin were effective in lowering (P < 0.05) the prevalence of M. haemolytica, whereas subtherpeutic tylosin had no effect. M. haemolytica isolated from control- and macrolide-treated animals were susceptible to macrolides as well as to other antibiotics. Major bacteria co-isolated with M. haemolytica included Pasteurella multocida, Staphylococcus spp., Acinetobacter spp., E. coli and Bacillus spp. With the exception of M. haemolytica and P. multocida, erythromycin resistance was frequently found in other isolated species. Both methods of macrolide administration increased (P < 0.05) the levels erythromycin-resistance enterococci in faeces. Development of resistance to injectable macrolides in bacteria isolated from the nasopharynx was species dependent. Therapeutic administration of tilmicosin and tularthromycin selected for macrolide resistant bacteria within both the respiratory and intestinal tract, whereas suptherapeutic administration of tylosin only selected for macrolide resistance in enteric bacteria.

Effects of increasing concentrations of glycerol in concentrate diets on nutrient digestibility, methane emissions, growth, fatty acid profiles, and carcass traits of lambs.

Abstract: Two experiments were conducted to evaluate the effects of increasing concentrations of glycerol in concentrate diets on total tract digestibility, methane (CH4) emissions, growth, fatty acid profiles, and carcass traits of lambs In both experiments, the control diet contained 57% barley grain, 145% wheat dried distillers grain with solubles (WDDGS), 13% sunflower hulls, 65% beet pulp, 63% alfalfa, and 3% mineral-vitamin mix Increasing concentrations (7, 14, and 21% dietary DM) of glycerol in the dietary DM were replaced for barley grain As glycerol was added, alfalfa meal and WDDGS were increased to maintain similar concentrations of CP and NDF among diets In Exp1, nutrient digestibility and CH4 emissions from 12 ram lambs were measured in a replicated 4 × 4 Latin square experiment In Exp 2, lamb performance was evaluated in 60 weaned lambs that were blocked by BW and randomly assigned to 1 of the 4 dietary treatments and fed to slaughter weight In Exp 1, nutrient digestibility and CH4 emissions were not altered (P = 015) by inclusion of glycerol in the diets In Exp2, increasing glycerol in the diet linearly decreased DMI (P < 001) and tended (P = 006) to reduce ADG, resulting in a linearly decreased final BW Feed efficiency was not affected by glycerol inclusion in the diets Carcass traits and total SFA or total MUFA proportions of subcutaneous fat were not affected (P = 077) by inclusion of glycerol, but PUFA were linearly decreased (P < 001) Proportions of 16:0, 10t-18:1, linoleic acid (18:2 n-6) and the n-6/n-3 ratio were linearly reduced (P < 001) and those of 18:0 (stearic acid), 9c-18:1 (oleic acid), linearly increased (P < 001) by glycerol When included up to 21% of diet DM, glycerol did not affect nutrient digestibility or CH4 emissions of lambs fed barley based finishing diets Glycerol may improve backfat fatty acid profiles by increasing 18:0 and 9c-18:1 and reducing 10t-18:1 and the n-6/n-3 ratio

Anti-Escherichia coli O157:H7 properties of purple prairie clover and sainfoin condensed tannins.

Abstract: Condensed tannins (CT) from purple prairie clover (PPC; Dalea purpurea Vent.) and sainfoin (SF; Onobrychis viciifolia) were assessed for anti-Escherichia coli activity by comparing their ability to react with proteins and liposome, cause cell aggregation, and alter outer membrane (OM) morphology and permeability. The PPC CT had greater (P < 0.01) protein-precipitating capacity than SF CT using either bovine serum albumin or ribulose 1,5-disphosphate carboxylase as model proteins. Minimum inhibitory concentration of PPC CT for two strains of E. coli and five strains of E. coli O157:H7 was four to six times lower than that of SF CT. E. coli exposed to 10 µg/mL of both CT had higher (P < 0.05) OM permeability than controls and was greater (P < 0.05) for PPC than for SF CT. Addition of both CT at 50 and 200 µg/mL caused cell aggregation which was more evident (P < 0.05) for PPC than for SF CT. Transmission electron microscopy showed electron dense material on the cell surface when cells were exposed to 50 µg/mL of PPC CT. The greater anti-E. coli activity of PPC than SF CT was due to its enhanced ability to precipitate protein that increased OM permeability and promoted cell aggregation.

Effect of dried distillers grains plus solubles on enteric methane emissions and nitrogen excretion from growing beef cattle.

Abstract: The objectives of this study were to examine the impact of corn- or wheat-based dried distillers grains with solubles (CDDGS or WDDGS) on enteric methane (CH4) emissions from growing beef cattle and determine if the oil in CDDGS was responsible for any response observed. Effects of CDDGS or WDDGS on total N excretion and partitioning between urine and fecal N were also examined in this replicated 4 × 4 Latin square using 16 ruminally cannulated crossbreed heifers (388.5 ± 34.9 kg of initial BW). The control diet contained (DM basis) 55% whole crop barley silage, 35% barley grain, 5% canola meal, and 5% vitamin and mineral supplement. Three dried distillers grains with solubles (DDGS) diets were formulated by replacing barley grain and canola meal (40% of dietary DM) with CDDGS, WDDGS, or WDDGS plus corn oil (WDDGS+oil). For WDDGS+oil, corn oil was added to WDDGS (4.11% fat DM basis) to achieve the same fat level as in CDDGS (9.95% fat DM basis). All total mixed diets were fed once daily ad libitum. Total collection of urine and feces was conducted between d 11 and 14. Enteric CH4 was measured between d 18 and 21 using 4 environmental chambers (2 animals fed the same diet per chamber). Methane emissions per kilogram of DM intake (DMI) and as percent of GE intake (GEI) among heifers fed WDDGS (23.9 g/kg DMI and 7.3% of GEI) and the control (25.3 g/kg DMI and 7.8% of GEI) were similar (P = 0.21 and P = 0.19) whereas heifers fed CDDGS (21.5 g/kg DMI and 6.6% of GEI) and WDDGS+oil (21.1 g/kg DMI and 6.3% of GEI) produced less (P < 0.05) CH4. Total N excretion (g/d) differed (P < 0.001) among treatments with WDDGS resulting in the greatest total N excretion (303 g/d) followed by WDDGS+oil (259 g/d), CDDGS (206 g/d), and the control diet (170 g/d), respectively. Compared with the control diet, heifers offered WDDGS, CDDGS, and WDDGS+oil excreted less fecal N (P < 0.001) but more (P < 0.001) urinary N. Results suggest that high-fat CDDGS or WDDGS+oil can mitigate enteric CH4 emissions in growing beef cattle. However, to completely assess the impact of DDGS on greenhouse gas emissions of growing feedlot cattle, the potential contribution of increased N excretion to heightened NH3 and nitrous oxide emissions requires consideration.

Enteric methane emission, diet digestibility, and nitrogen excretion from beef heifers fed sainfoin or alfalfa.

Abstract: Effects of plant-bound condensed tannin (CT)-containing sainfoin vs. CT-free alfalfa (or low-CT alfalfa-sainfoin mixture), plant stage of maturity, and their interaction on enteric methane (CH4) emissions, diet digestibility, and N excretion were studied, using 8 ruminally cannulated beef heifers in 2 sequential short-term experiments (Exp. 1 and 2). In Exp. 1, first growth legumes were harvested daily and offered fresh to heifers. Heifers were assigned to 100% sainfoin or 80% alfalfa:20% sainfoin (as-fed basis). Responses were measured at early (late vegetative to early bud; stage 2 to 3) and late (early flower; stage 5) stage of maturity. In Exp. 2, the same legumes were harvested from second growth (late bud; stage 4) and offered to heifers as hay; 100% sainfoin or 100% alfalfa. In both experiments, heifers were fed once daily at 1× maintenance. When fed as fresh forage (Exp. 1), sainfoin, compared with the alfalfa-sainfoin blend, had greater digestibility of OM (74.7 vs. 70.9%; P = 0.02), yet tended to have lower CP digestibility (73.2 vs. 77.1%; P = 0.059). There was no difference between fresh legumes for CH4 emissions [25.9 g/kg DMI ± 4.02 SE; 8.5% of gross energy intake (GEI) ± 1.26 SE; or 36.8 g/kg digested OM ± 1.75 SE]. The fresh legumes were more digestible at early, rather than at late, maturity and, consequently, enteric CH4 (27.4 vs. 24.4 g/kg DMI; P < 0.004; 8.9 vs. 8.1% GEI; P < 0.008) was greater at early, rather than at later, growth. When fed as hay (Exp. 2), sainfoin, compared with alfalfa, had greater digestibility of OM (60.5 vs. 50.3%; P = 0.007), lower digestibility of CP (64.2 vs. 68.8%; P = 0.004), yet there was no difference between the legume hays for CH4 emissions (22.4 g/kg DMI ± 1.29 SD and 7.1% GEI ± 0.40 SD). However, on the basis of OM digested, CH4 emissions were lower for sainfoin than alfalfa hay (44.3 vs. 59.0 g/kg; P = 0.008). Percentage of total N excretion in urine was less for sainfoin compared with alfalfa, both for fresh legumes in Exp. 1 (74 vs. 78%; P = 0.017) or hay in Exp. 2 (64 vs. 72%; P < 0.001), and increasing maturity lowered urinary N excretion. In conclusion, feeding CT-containing sainfoin partially shifted N excretion from urine to feces, but it had little impact on enteric CH4 emissions from beef cattle fed at maintenance as compared with feeding either 80% alfalfa:20% sainfoin (fresh forages) or 100% alfalfa (hay). Feeding fresh legumes harvested between the late vegetative to early bud stage, compared with harvested at the early flower stage, increased N excreted in urine as well as enteric CH4 emissions from beef cattle fed at maintenance.

Biochemical analysis of a highly specific, pH stable xylanase gene identified from a bovine rumen-derived metagenomic library.

Abstract: A metagenomic library was generated using microbial DNA extracted from the rumen contents of a grass hay-fed dairy cow using a bacterial artificial chromosome-based vector system. Functional screening of the library identified a gene encoding a potent glycoside hydrolase, xyn10N18, localised within a xylanolytic gene cluster consisting of four open-reading frames (ORFs). The ORF, xyn10N18, encodes an endo-β-1,4-xylanase with a glycosyl hydrolase family 10 (GH10) catalytic domain, adopts a canonical α8/s8-fold and possesses conserved catalytic glutamate residues typical of GH10 xylanases. Xyn10N18 exhibits optimal catalytic activity at 35 °C and pH 6.5 and was highly stable to pH changes retaining at least 85 % relative catalytic activity over a broad pH range (4.0–12.0). It retained 25 % of its relative activity at both low (4 °C) and high (55 °C) temperatures, however the stability of the enzyme rapidly decreased at temperatures of >40 °C. The specific activity of Xyn10N18 is enhanced by the divalent cations Mn2+ and Co2+ and is dramatically reduced by Hg2+ and Cu2+. Interestingly, EDTA had little effect on specific activity indicating that divalent cations do not function mechanistically. The enzyme was highly specific for xylan containing substrates and showed no catalytic activity against cellulose. Analysis of the hydrolysis products indicated that Xyn10N18 was an endoxylanase. Through a combination of structural modelling and in vitro enzyme characterisation this study provides an understanding of the mechanism and the substrate specificity of this enzyme serving as a starting point for directed evolution of Xyn10N18 and subsequent downstream use in industry.

Effects of extracts of Humulus lupulus (hops) and Yucca schidigera applied alone or in combination with monensin on rumen fermentation and microbial populations in vitro

Abstract: Background β-Acids in hops (Humulus lupulus) and saponins in yucca (Yucca schidigera) have been found to possess antimicrobial properties similar to that of monensin and could be an alternative to in-feed antibiotics. The effects of monensin (MON) and ethanol extracts of hops (HE) and Y. schidigera (YE) alone and in combination with MON were assessed on ruminal microbial composition and fermentation in vitro of a barley-based diet. Results All treatments decreased (P < 0.05) CH4 production (per unit of dry matter), microbial protein (mg), and NH3-N accumulation. All treatments reduced (P < 0.01) the acetate:propionate (A:P) ratio and molar proportions of butyrate, but increased (P < 0.01) those of propionate, whereas those of acetate decreased (P < 0.001) with addition of MON (10 µg mL−1) and combined with HE or YE. Methane produced per unit of true digested dry matter decreased (P < 0.001) with all treatments except YE. Monensin reduced (P < 0.001) proportions of 16S rRNA copies of Ruminococcus flavefaciens, but increased (P < 0.01) those of Selenomonas ruminantium. Hops extract alone or combined with MON reduced (P < 0.01) proportions of R. flavefaciens but combined with MON tended (P < 0.1) to increase those of S. ruminantium. Yucca extract combined with MON increased (P < 0.01) the proportions of R. flavefaciens and S. ruminantium. All treatments except MON (2.5 µg mL−1) reduced (P < 0.01) the relative abundance of methanogens. Conclusion Hops extract and YE altered rumen microbes and fermentation in a manner similar to MON with many responses being additive when applied in combination. © 2013 Society of Chemical Industry

Methodological comparisons for antimicrobial resistance surveillance in feedlot cattle

Abstract: Background The purpose of this study was to objectively compare methodological approaches that might be utilized in designing an antimicrobial resistance (AMR) surveillance program in beef feedlot cattle. Specifically, four separate comparisons were made to investigate their potential impact on estimates for prevalence of AMR. These included investigating potential differences between 2 different susceptibility testing methods (broth microdilution and disc diffusion), between 2 different target bacteria (non-type-specific E. coli [NTSEC] and Mannheimia haemolytica), between 2 strategies for sampling feces (individual samples collected per rectum and pooled samples collected from the pen floor), and between 2 strategies for determining which cattle to sample (cattle that were culture-positive for Mannheimia haemolytica and those that were culture-negative).

New Sainfoin Populations for Bloat-free Alfalfa Pasture Mixtures in Western Canada

Abstract: Sainfoin (Onobrychis viciifolia Scop.), a condensed-tannin-containing legume, when present in alfalfa (Medicago sativa L.) pasture prevents bloat in grazing cattle. However, old sainfoin cultivars do not persist in alfalfa stands for long and in new mixed stands do not regrow at the same rate as alfalfa after cutting or grazing. This multiyear and multilocation study was initiated to determine if new sainfoin germplasm developed for their ability to survive with alfalfa can perform better than old cultivars in western Canada. In this study new sainfoin populations in pure stands persisted same as ‘Nova’ for 4 yr. In hay trials at Lethbridge under rain-fed and irrigated conditions, four (3432, 3519, 3900, and 3902) and three (3519, 3901, and 3902) new sainfoin populations produced significantly higher dry matter (DM) than Nova, respectively. In another set of tests where multiple harvests were taken at Lethbridge (irrigation) and Saskatoon (rain-fed), the new sainfoin populations produced higher DM yields than Nova in pure stands, persisted for three production years in mixed stands while contributing >20% DM for bloat prevention at each harvest. Nova proportions in mixed alfalfa stands decreased after the first production year. At Swift Current, however, new sainfoin populations produced significantly lower DM yield than Nova in pure stands and similar DM yield and proportions in mixed stands. Therefore, the new sainfoin populations tested may help improve hay or pasture production in most, but not in all, parts of western Canada. S. Acharya, E. Sottie, McAllister, and Y. Wang, Agriculture and AgriFood Canada Research Centre, 5403 – 1st Ave. South, Lethbridge, AB T1J 4B1, Canada; B. Coulman, Univ. of Saskatchewan, 51 Campus Dr., Saskatoon, SK S7N 5A8, Canada; A. Iwaasa, Agriculture and AgriFood Canada, 1 Airport Rd., Swift Current, SK S9H 3X2, Canada; J. Liu, Inner Mongolia Agriculture Univ., Hohhot, PR China 010018. Received 15 Oct. 2012. *Corresponding author (acharya@agr.gc.ca). Abbreviations: DM, dry matter; LRC, Lethbridge Research Centre. Published in Crop Sci. 53:2283–2293 (2013). doi: 10.2135/cropsci2012.10.0591 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Published July 26, 2013

Effects of crude glycerin supplementation on wool production, feeding behavior, and body condition of merino ewes.

Abstract: The increasing availability of crude glycerin from the biodiesel industry has led to an interest in its use as an energy source in ruminant diets. However, its effects on ruminal fermentation patterns and methane (CH ) production are unclear, and there are no reports on the effect of its inclusion in the diet on wool production or growth of Merino sheep. Thus, the objectives of this study were to determine the effects of increasing levels of crude glycerin on in vitro ruminal fermentation and CH production and DMI, BW, feeding behavior, and wool growth and quality in Merino ewes. Crude glycerin (99.2% pure, colorless, odorless, viscous liquid) replaced whole wheat grain in completely pelleted diets at levels of 0%, 6%, and 12% DM in both in vitro and in vivo studies. For in vitro studies, diets were dried and ground through a 1-mm screen and incubated on 2 different days for 24 h. Modified McDougal's buffer and rumen liquor were mixed 3:1, and gas production and CH concentration was measured after 6, 12, and 24 h of incubation with pH and IVDMD measured at 24 h. Cumulative gas (mL/g DM) and methane (mL) production was similar (P ≥ 0.35) among dietary treatments. In vitro dry matter disappearance (%) increased (P < 0.01) with increasing concentrations of crude glycerin. For the in vivo study, 39 Merino ewes were randomly assigned to 3 treatments (n = 13 ewes/treatment). Pelleted diets were available continuously for a 10-wk period through the use of automatic feeders. Ewes were weighed every 7 d. Wool yield was determined on mid-side patches of 100 cm shorn at d 0 and d 70. Dye bands were used to determine wool growth and fiber length. Intake and ADG were similar among treatments (P = 0.59). Neither wool yield, length, spinning fineness, nor fiber diameter (μm) were affected after supplementation with crude glycerin (P ≥ 0.13). This study indicates the potential for crude glycerin to be included in the diets of Merino sheep at up to 12% DM without negatively affecting wool yield and quality.

Susceptibility to tulathromycin in Mannheimia haemolytica isolated from feedlot cattle over a 3-year period

Abstract: Mannheimia haemolytica isolated from feedlot cattle were tested for tulathromycin resistance. Cattle were sampled over a three-year period, starting 12 months after approval of tulathromycin for prevention and treatment of bovine respiratory disease. Nasopharyngeal samples from approximately 5,814 cattle were collected when cattle entered feedlots (N = 4) and again from the same cattle after ≥ 60 d on feed. The antimicrobial use history for each animal was recorded. Mannheimia haemolytica was isolated from 796 (13.7%) entry samples and 1,038 (20.6%) ≥ 60 d samples. Of the cattle positive for M. haemolytica, 18.5%, 2.9%, and 2.4% were administered therapeutic concentrations of tulathromycin, tilmicosin, or tylosin tartrate, respectively. In addition, 13.2% were administered subtherapeutic concentrations of tylosin phosphate in feed. In years one and two, no tulathromycin-resistant M. haemolytica were detected, whereas 5 isolates (0.4%) were resistant in year three. These resistant isolates were collected from three cattle originating from a single pen, were all serotype 1, and were genetically related (≥ 89% similarity) according to pulsed-field gel electrophoreses patterns. The five tulathromycin-resistant isolates were multi-drug resistant also exhibiting resistance to oxytetracycline, tilmicosin, ampicillin, or penicillin. The macrolide resistance genes erm(42), erm(A), erm(B), erm(F), erm(X) and msr(E)-mph(E), were not detected in the tulathromycin-resistant M. haemolytica. This study showed that tulathromycin resistance in M. haemolytica from a general population of feedlot cattle in western Canada was low and did not change over a three-year period after tulathromycin was approved for use in cattle.

Effects of hop varieties on ruminal fermentation and bacterial community in an artificial rumen (rusitec)

Abstract: BACKGROUND: There is a growing interest in the use of hops (Humulus lupulus) as an alternative to antibiotics to manipulate ruminal fermentation. However, the effects of different hop varieties on ruminal fermentation and bacterial populations have not been studied. Here the effects of three hop varieties, Cascade (CAS), Millennium (MIL) and Teamaker (TM), at a level of 800 µg mL−1 inoculum on ruminal fermentation and microbial populations in an artificial rumen system (rusitec) fed a barley silage-based total mixed ration were investigated. Bacterial populations were assessed using real-time polymerase chain reaction and expressed as a percentage of total bacterial 16S rRNA gene copies. RESULTS: All hops reduced (P < 0.001) total gas, methane and the acetate:propionate ratio. Liquid-associated Fibrobacter succinogenes, Ruminococcus albus and Streptococcus bovis were reduced (P < 0.05) by MIL and TM. Feed particle-associated S. bovis was reduced (P < 0.01) by MIL and TM, but TM and CAS increased (P < 0.01) Ruminobacter amylophilus and Prevotella bryantii respectively. Methanogens were decreased (P < 0.05) by MIL in both liquid and solid fractions and by CAS in the solid fraction. The total amount of α- and β-acids in hops affected the ruminal fermentation. CONCLUSION: Hop-induced changes in fermentation and microbial populations may improve energy efficiency use in the rumen. Further research is needed to determine the effects of hops on in vivo ruminal fermentation, microbial populations and animal performance. Copyright © 2012 Society of Chemical Industry

Biodegradation of specified risk material and fate of scrapie prions in compost

Abstract: Composting may be a viable alternative to rendering and land filling for the disposal of specified risk material (SRM) provided that infectious prion proteins (PrPTSE) are inactivated. This study investigated the degradation of SRM and the fate of scrapie prions (PrPSc) over 28 days in laboratory-scale composters, with and without feathers in the compost matrices. Compost was mixed at day 14 to generate a second heating cycle, with temperatures exceeding 65°C in the first cycle and 50°C in the second cycle. Approximately 63% and 77% of SRM was degraded after the first and second cycles, respectively. Inclusion of feathers in the compost matrices did not alter compost properties during composting other than increasing (P < 0.05) total nitrogen and reducing (P < 0.05) the C/N ratio. However, addition of feathers enhanced (P < 0.05) SRM degradation by 10% upon completion of experiment. Scrapie brain homogenates were spiked into manure at the start of composting and extracted using sodium dodecyl sulphate fol...

Elucidation of Molecular Mechanisms of Physiological Variations between Bovine Subcutaneous and Visceral Fat Depots under Different Nutritional Regimes

Abstract: Adipose tissue plays a critical role in energy homeostasis and metabolism. There is sparse understanding of the molecular regulation at the protein level of bovine adipose tissues, especially within different fat depots under different nutritional regimes. The objective of this study was to analyze the differences in protein expression between bovine subcutaneous and visceral fat depots in steers fed different diets and to identify the potential regulatory molecular mechanisms of protein expression. Subcutaneous and visceral fat tissues were collected from 16 British-continental steers (15.5 month old) fed a high-fat diet (7.1% fat, n=8) or a control diet (2.7% fat, n=8). Protein expression was profiled using label free quantification LC-MS/MS and expression of selected transcripts was evaluated using qRT-PCR. A total of 682 proteins were characterized and quantified with fat depot having more impact on protein expression, altering the level of 51.0% of the detected proteins, whereas diet affected only 5.3%. Functional analysis revealed that energy production and lipid metabolism were among the main functions associated with differentially expressed proteins between fat depots, with visceral fat being more metabolically active than subcutaneous fat as proteins associated with lipid and energy metabolism were upregulated. The expression of several proteins was significantly correlated to subcutaneous fat thickness and adipocyte size, indicating their potential as adiposity markers. A poor correlation (r=0.245) was observed between mRNA and protein levels for 9 genes, indicating that many proteins may be subjected to post-transcriptional regulation. A total of 8 miRNAs were predicted to regulate more than 20% of lipid metabolism proteins differentially expressed between fat depots, suggesting that miRNAs play a role in adipose tissue regulation. Our results show that proteomic changes support the distinct metabolic and physiological characteristics observed between subcutaneous and visceral adipose tissue depots in cattle.

The production and characterization of a new active lipase from Acremonium alcalophilum using a plant bioreactor

Abstract: Microorganisms are the most proficient decomposers in nature, using secreted enzymes in the hydrolysis of lignocellulose. As such, they present the most abundant source for discovery of new enzymes. Acremonium alcalophilum is the only known cellulolytic fungus that thrives in alkaline conditions and can be cultured readily in the laboratory. Its optimal conditions for growth are 30°C and pH 9.0-9.2. The genome sequence of Acremonium alcalophilum has revealed a large number of genes encoding biomass-degrading enzymes. Among these enzymes, lipases are interesting because of several industrial applications including biofuels, detergent, food processing and textile industries. We identified a lipA gene in the genome sequence of Acremonium alcalophilum, encoding a protein with a predicted lipase domain with weak sequence identity to characterized enzymes. Unusually, the predicted lipase displays ≈ 30% amino acid sequence identity to both feruloyl esterase and lipase of Aspergillus niger. LipA, when transiently produced in Nicotiana benthamiana, accumulated to over 9% of total soluble protein. Plant-produced recombinant LipA is active towards p-nitrophenol esters of various carbon chain lengths with peak activity on medium-chain fatty acid (C8). The enzyme is also highly active on xylose tetra-acetate and oat spelt xylan. These results suggests that LipA is a novel lipolytic enzyme that possesses both lipase and acetylxylan esterase activity. We determined that LipA is a glycoprotein with pH and temperature optima at 8.0 and 40°C, respectively. Besides being the first heterologous expression and characterization of a gene coding for a lipase from A. alcalophilum, this report shows that LipA is very versatile exhibiting both acetylxylan esterase and lipase activities potentially useful for diverse industry sectors, and that tobacco is a suitable bioreactor for producing fungal proteins.

Assessing the inactivation of Mycobacterium avium subsp. paratuberculosis during composting of livestock carcasses.

Abstract: Mycobacterium avium subsp. paratuberculosis causes Johne's disease (JD) in ruminants, with substantial economic impacts on the cattle industry. Johne's disease is known for its long latency period, and difficulties in diagnosis are due to insensitivities of current detection methods. Eradication is challenging as M. avium subsp. paratuberculosis can survive for extended periods within the environment, resulting in new infections in naive animals (W. Xu et al., J. Environ. Qual. 38:437-450, 2009). This study explored the use of a biosecure, static composting structure to inactivate M. avium subsp. paratuberculosis. Mycobacterium smegmatis was also assessed as a surrogate for M. avium subsp. paratuberculosis. Two structures were constructed to hold three cattle carcasses each. Naturally infected tissues and ground beef inoculated with laboratory-cultured M. avium subsp. paratuberculosis and M. smegmatis were placed in nylon and plastic bags to determine effects of temperature and compost environment on viability over 250 days. After removal, samples were cultured and growth of both organisms was assessed after 12 weeks. After 250 days, M. avium subsp. paratuberculosis was still detectable by PCR, while M. smegmatis was not detected after 67 days of composting. Furthermore, M. avium subsp. paratuberculosis remained viable in both implanted nylon and plastic bags over the composting period. As the compost never reached a homogenous thermophilic (55 to 65°C) state throughout each structure, an in vitro experiment was conducted to examine viability of M. avium subsp. paratuberculosis after exposure to 80°C for 90 days. Naturally infected lymph tissues were mixed with and without compost. After 90 days, M. avium subsp. paratuberculosis remained viable despite exposure to temperatures typically higher than that achieved in compost. In conclusion, it is unlikely composting can be used as a means of inactivating M. avium subsp. paratuberculosis associated with cattle mortalities.

Effects of increasing levels of corn dried distillers grains with solubles and monensin on intake, digestion, and ruminal fermentation in beef heifers fed high-barley grain diets.

Abstract: The objective of this study was to determine whether increasing corn-based dried distillers grains with solubles (DDGS) in high-barley grain diets reduces the merit of using higher levels of monensin by assessing intake, digestibility, and ruminal pH and fermentation in feedlot heifers. Five ruminally and duodenally cannulated Angus heifers (average BW of 599±36 kg) were used in a 5×5 Latin square with a 2×2+1 factorial arrangement. Treatments were control (CON, 10% barley silage, 90% barley-based concentrate, and 28 mg monensin/kg DM) and diets substituting 20% (LDG) or 40% (HDG) DDGS for barley grain with 28 mg (ML) or 48 mg (MH) monensin/kg diet DM: 1) CONML, 2) LDGML, 3) HDGML, 4) LDGMH, and 5) HDGMH. Contrasts compared LDG vs. HDG, ML vs. MH, interactions between DDGS and monensin, and the effect of increasing DDGS in the diet. Increasing DDGS quadratically (P<0.01) increased DMI. There was no interaction for DMI between the dietary inclusion rate of DDGS and the dose of monensin; however, DMI was reduced (P<0.05) for heifers fed MH vs. ML. Ruminal digestibility of OM, NDF, and starch linearly decreased (P<0.01), but intestinal digestibility linearly increased (P<0.01) with increasing DDGS, resulting in no differences in total tract digestibility. Ruminal digestibility of OM was greater (P<0.04) in heifers fed MH than ML; however, the total tract digestibility of OM was not affected. Intake of N, flows of total N, nonammonia N, and dietary N were linearly (P<0.02) increased, and the efficiency of ruminal microbial synthesis linearly (P<0.04) improved with increasing DDGS. Increasing DDGS inclusion linearly decreased (P<0.04) the acetate to propionate ratio. Inclusion of MH decreased (P<0.04) acetate and increased (P<0.05) NH3-N compared to ML, but high monensin did not affect mean ruminal pH, the duration of pH<5.8, 5.5, 5.2, or the area below the curve at pH 5.8, 5.5, and 5.2, indicating that there was no evidence that it modulated ruminal pH. These results suggest that feeding monensin at 48 vs. 28 mg/kg diet DM altered nutrient availability and site of feed digestion, likely as a result of reduced DMI and increased ruminal digestion of DM. High levels of monensin may reduce the risk of acidosis through a reduction in DMI, but in the present study this was not evident in differences in the ruminal pH profiles between heifers fed ML and MH diets.

Effect of dried distillers’ grains with solubles on enteric methane emissions and nitrogen excretion from finishing beef cattle

Abstract: Hunerberg, M., McGinn, S. M., Beauchemin, K. A., Okine, E. K., Harstad, O. M. and McAllister, T. A. 2013. Effect of dried distillers’ grains with solubles on enteric methane emissions and nitrogen excretion from finishing beef cattle. Can. J. Anim. Sci. 93: 373–385. The objective of this study was to examine the impact of corn- or wheat-based dried distillers’ grains with solubles (CDDGS, WDDGS) on enteric methane (CH₄) emissions from finishing beef cattle, and to determine if any observed reductions were a result of the fat content of CDDGS. A second objective was to compare the effect of CDDGS or WDDGS on N excretion. The experiment was designed as replicated 4×4 Latin square with 28-d periods using 16 ruminally fistulated crossbred heifers. The control diet contained 87% barley grain, 8% barley silage and 5% supplement (dry matter; DM basis). Treatment diets were formulated by replacing 40% DM of barley grain with CDDGS, WDDGS, or corn oil supplemented WDDGS (WDDGS+oil). For the WDDGS+oil diet 6.5% corn oil was added to WDDGS (3.4% fat DM) to achieve a similar fat level as in CDDGS (9.7% DM). All diets were fed as total mixed rations once daily ad libitum. Total collection of urine and faeces was conducted between days 18 and 21. Methane was measured between days 25 and 28 using four identical open circuit respiratory chambers. Compared with WDDGS, feeding CDDGS and WDDGS+oil reduced (P<0.05) CH₄ emissions as a percentage of gross energy intake (GEI) from 5.5 to 4.0 and 4.2%, respectively. Feeding CDDGS also reduced (P<0.05) CH₄ emissions compared with the control (5.0% of GEI), while WDDGS+oil tended (P=0.08) to elicit a similar response. Methane (% of GEI) between WDDGS and the control did not differ (P=0.29). Excretion of total N was greater (P<0.001) for CDDGS, WDDGS and WDDGS+oil (220, 253, and 265 g d⁻¹) compared with the control (143 g d⁻¹). Although oil appears to be responsible for reducing CH₄ emissions when DDGS is included in the diet, increased N excretion requires that a complete life cycle assessment be conducted to assess the full impact of DDGS on greenhouse gas emissions from finishing cattle.

Evaluation of the Feed Value for Ruminants of Blends of Corn and Wheat Distillers Dried Grains

Abstract: Recently, biofuel processing has produced a large amount of biofuel coproducts. However, to date, there is little information on the metabolic characteristics of proteins and energy in biofuel coproduct-based rations. The objective of this study was to study the metabolic characteristics of proteins and energy in biofuel coproduct-based rations in terms of (1) chemical and nutrient profiles, (2) protein and carbohydrate subfraction associated with various degradation rate, (3) rumen and intestinal degradation and digestion kinetics, and (4) metabolic characteristics of proteins. Two sources of grain corn were mixed with two sources of biofuel coproducts (wheat-based dried distillers grains with solubles, wDDGS) in ratios of 100:0, 75:25, 50:50, and 25:75%. The study revealed that increasing the biofuel coproduct inclusion level increased most of the nutritional components linearly (P < 0.05) except starch, which linearly decreased. With increasing biofuel coproduct inclusion level, the rumen degradation r...

Quality and precision processing of barley grain affected intake and digestibility of dry matter in feedlot steers

Abstract: Yang, W. Z., Oba, M. and McAllister, T. A. 2013. Quality and precision processing of barley grain affected intake and digestibility of dry matter in feedlot steers. Can. J. Anim. Sci. 93: 251–260. A study was conducted to determine the impact of barley quality and precision processing to account for the impact of variable kernel uniformity on ruminal pH and fermentation, and digestibility in the digestive tract of steers. Eight ruminally cannulated steers were used in a replicated 4×4 Latin square experiment. The four diets consisted of light-weight barley (LB) precision-processed with roller setting based on kernel size; heavy-weight barley (HB) precision-processed; LB and HB grain mixed equal parts then processed at a single roller setting (CON); or LB and HB precision-processed and mixed equal parts (PP). The diets consisted of 10% barley silage and 90% concentrate [dry matter (DM) basis]. Dry matter intake by steers fed LB was greater (P=0.04) than by steers fed HB. Intakes of DM and other nutrients were greater (P=0.04) for steers fed PP than for steers fed CON. There were no differences (P>0.14) in ruminal pH and fermentation among treatments. Digestibility of DM in the total digestive tract tended (P=0.06) to be less with LB than with HB. Precision processing increased digestibility of crude proteion (P=0.04) and acid detergent fibre (P=0.06) resulting in a trend (P=0.10) towards increasing organic matter digestibility as compared with CON. The results suggest that screening of blended barley into more uniform fractions and precision processing of each fraction could increase intake of digestible nutrients for feedlot cattle.

Precision processing barley grain did not affect productivity of lactating dairy cows

Abstract: Schlau, N., Duineveld, L., Yang, W. Z., McAllister, T. A. and Oba, M. 2013. Precision processing barley grain did not affect productivity of lactating dairy cows. Can. J. Anim. Sci. 93: 261–268. This study evaluated the effects of precision processing (PP; processing based on kernel size) barley grain on ruminal fermentation and productivity of lactating dairy cows. Twenty multiparous Holstein cows, including eight ruminally cannulated cows, were used in a replicated 4×4 Latin square design with 21-d periods. Diets contained light barley grain processed precisely using a narrow roller setting (LB), heavy barley processed precisely using a wide roller setting (HB), processed HB and LB mixed at equal proportions (PP), or equal parts of light and heavy barley grain processed at a single narrow roller setting (CON). All diets consisted of 40% barley grain, 40% barley silage, and 20% of a supplement premix. Comparisons were made between LB and HB to evaluate the effect of barley quality, and between PP and CON...