J. J. McKinnon

Characterization of the Core Rumen Microbiome in Cattle during Transition from Forage to Concentrate as Well as during and after an Acidotic Challenge

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 OTUs 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.

Heat-induced protein structure and subfractions in relation to protein degradation kinetics and intestinal availability in dairy cattle

The objectives of this study were to reveal protein structures of feed tissues affected by heat processing at a cellular level, using the synchrotron-based Fourier transform infrared microspectroscopy as a novel approach, and quantify protein structure in relation to protein digestive kinetics and nutritive value in the rumen and intestine in dairy cattle. The parameters assessed included 1) protein structure alpha-helix to beta-sheet ratio; 2) protein subfractions profiles; 3) protein degradation kinetics and effective degradability; 4) predicted nutrient supply using the intestinally absorbed protein supply (DVE)/degraded protein balance (OEB) system for dairy cattle. In this study, Vimy flaxseed protein was used as a model feed protein and was autoclave-heated at 120 degrees C for 20, 40, and 60 min in treatments T1, T2, and T3, respectively. The results showed that using the synchrotron-based Fourier transform infrared microspectroscopy revealed and identified the heat-induced protein structure changes. Heating at 120 degrees C for 40 and 60 min increased the protein structure alpha-helix to beta-sheet ratio. There were linear effects of heating time on the ratio. The heating also changed chemical profiles, which showed soluble CP decreased upon heating with concomitant increases in nonprotein nitrogen, neutral, and acid detergent insoluble nitrogen. The protein subfractions with the greatest changes were PB1, which showed a dramatic reduction, and PB2, which showed a dramatic increase, demonstrating a decrease in overall protein degradability. In situ results showed a reduction in rumen-degradable protein and in rumen-degradable dry matter without differences between the treatments. Intestinal digestibility, determined using a 3-step in vitro procedure, showed no changes to rumen undegradable protein. Modeling results showed that heating increased total intestinally absorbable protein (feed DVE value) and decreased degraded protein balance (feed OEB value), but there were no differences between the treatments. There was a linear effect of heating time on the DVE and a cubic effect on the OEB value. Our results showed that heating changed chemical profiles, protein structure alpha-helix to beta-sheet ratio, and protein subfractions; decreased rumen-degradable protein and rumen-degradable dry matter; and increased potential nutrient supply to dairy cattle. The protein structure alpha-helix to beta-sheet ratio had a significant positive correlation with total intestinally absorbed protein supply and negative correlation with degraded protein balance.

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 < 0.03) by diet, with only 14 genera, representing >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.

Influence of dry heat treatment of canola meal on site and extent of nutrient disappearance in ruminants

A study was conducted to determine the effects of temperature and duration of heating (125 or 145 °C for 10, 20 or 30 min) on ruminal, intestinal and total tract disappearance of the dry matter (DM) and crude protein (CP) fractions of canola meal. Two steers fitted with rumen and duodenal cannulas were utilized. The effects of heating on ruminal disappearance of DM and CP were determined by incubating samples in the rumen for 2, 4, 6, 8, 12, and 24 h. Partitioning DM and CP disappearance between the rumen, intestines (small and large) and total tract was accomplished using the mobile nylon bag technique. Relative to the unheated control meal, heating at 125 or 145 °C reduced (P < 0.05) ruminal DM and CP disappearance. Relative to the control, no effects of heating to 125 °C were observed on intestinal DM or CP disappearance with the exception that samples heated for 20 or 30 min and incubated in the rumen for 24 h had higher (P < 0.05) intestinal DM disappearance values. Heating to 145 °C reduced (P < 0.05) intestinal DM disappearance relative to the control, particularly for samples heated for 30 min. Heating to 145 °C reduced (P < 0.05) intestinal CP disappearance across all rumen incubation times. No differences between the control and meals heated to 125 °C were found in total tract DM and CP disappearance, indicating no negative effects of heating to 125 °C on nutrient digestion. Heating to 145 °C reduced (P < 0.05) both total tract DM and CP disappearance. Acid detergent insoluble nitrogen content of the treated meal was negatively related to intestinal (r2 = 0.78) and total tract (r2 = 0.82) CP disappearance. It is concluded that heating CM to a temperature of 145 °C will reduce ruminal and total tract availability of the DM and CP fractions. Heating to 125 °C for 10, 20 or 30 min will reduce rumen disappearance of both DM and CP but will not significantly reduce the disappearance of CP over the total tract of the ruminant. These results indicate that short duration heating of canola meal to 125 °C, is an effective method of increasing rumen undegradable protein content without impairing intestinal digestibility.

Characterization of rumen bacterial diversity and fermentation parameters in concentrate fed cattle with and without forage

Aims:  To determine the effects of the removal of forage in high‐concentrate diets on rumen fermentation conditions and rumen bacterial populations using culture‐independent methods.

A potential association between the BM 1500 microsatellite and fat deposition in beef cattle.

Abstract. The obese gene was hypothesized as a candidate gene for fat characteristics in beef cattle. The BM 1500 microsatellite, near the obese gene, was characterized in 158 purebred beef bulls for which carcass trait information was available. Four breeds were included in the analyses—Angus, Charolais, Hereford, and Simmental. Four alleles were found. Lengths were approximately 138, 147, 149, and 140 bp with genotypic frequencies of 0.47, 0.44, 0.09, and 0.003 respectively. The carcass traits %rib fat, %rib lean, average fat, and grade fat were found to be significantly associated with the different alleles. The presence of the 138-bp allele in the genotype of an animal is correlated with higher levels of fat, whereas the 147-bp allele has the opposite effect. The 149-bp allele was found in low numbers, and a homozygote was never identified. Hereford and Angus bulls had the greatest frequencies of 138-bp alleles (Hereford = 0.57, Angus = 0.59), while Charolais and Simmental had a greater proportion of 147-bp alleles (Charolais = 0.54, Simmental = 0.58). This information may aid cattle producers in selecting cattle for markets that differ in the amount of fat required.

Substitution of wheat dried distillers grains with solubles for barley grain or barley silage in feedlot cattle diets: Intake, digestibility, and ruminal fermentation1

The objective of this study was to evaluate the effects of substituting wheat dried distillers grains with solubles (DDGS) for barley grain and barley silage on intake, digestibility, and ruminal fermentation in feedlot beef cattle. Eight ruminally cannulated Angus heifers (initial BW 455 ± 10.8 kg) were assigned to a replicated 4 × 4 Latin square design with 4 treatments: control, low (25%), medium (30%), and high (35%) wheat DDGS (DM basis). The diets consisted of barley silage, barley concentrate, and wheat DDGS in ratios of 15:85:0 (CON), 10:65:25 (25DDGS), 5:65:30 (30DDGS), and 0:65:35 (35DDGS; DM basis), respectively. The diets were formulated such that wheat DDGS was substituted for both barley grain and barley silage to evaluate whether wheat DDGS can be fed as a source of both energy (grain) and fiber in feedlot finishing diets. Intakes (kg/d) of DM and OM were not different, whereas those of CP, NDF, ADF, and ether extract (EE) were greater (P < 0.01) and intake of starch was less (P < 0.01) for the 25DDGS compared with the CON diet. The digestibilities of CP, NDF, ADF, and EE in the total digestive tract were greater (P < 0.05) for 25DDGS vs. CON. Ruminal pH and total VFA concentrations were not different (P > 0.15) between 25DDGS and CON diets. Replacing barley silage with increasing amounts of wheat DDGS (i.e., from 25DDGS to 35DDGS) linearly reduced (P < 0.05) intakes of DM and other nutrients without altering (P=0.40) CP intake. In contrast, digestibilities of DM and other nutrients in the total digestive tract linearly increased (P < 0.05) with increasing wheat DDGS except for that of EE. Additionally, with increasing amounts of wheat DDGS, mean ruminal pH tended (P=0.10) to linearly decrease, and ruminal pH status decreased with longer (P=0.04) duration of pH <5.5 and <5.2, and greater (P=0.01) curve area under pH <5.8 and <5.5 without altering (P > 0.19) ruminal VFA and NH(3)-N concentrations. Results indicated that wheat DDGS can be effectively used to replace both barley grain and silage at a moderate amount to meet energy and fiber requirements of finishing cattle. However, when silage content of the diet is low (<10%), wheat DDGS is not an effective fiber source, so replacing forage fiber with wheat DDGS in finishing diets decreases overall ruminal pH status even though the rapidly fermentable starch content of the diet is considerably reduced.

Effect of variety and maturity stage on chemical composition, carbohydrate and protein subfractions, in vitro rumen degradability and energy values of timothy and alfalfa

The objective of this study was to investigate the effects of forage variety and stage of maturity on chemical composition, protein and carbohydrate subfractions, in vitro rumen degradability and energy content under the climatic conditions of western Canada. Two varieties of alfalfa (Medicago sativa L. cvs. Pioneer and Beaver) and timothy (Phleum pratense L. cvs. Climax and Joliette), grown at three locations in Saskatchewan (Canada), were cut at three stages [1 = 1 wk before commercial cut (early bud for alfalfa; joint for timothy); 2 = at commercial cut (late bud for alfalfa; pre-bloom head for timothy); and 3 = one week after commercial cut (early bloom for alfalfa; full head for timothy)]. The results showed that: (1) the varieties had minimal effects on nutritional value; however, (2) stage of cutting had a large impact on chemical composition, protein and carbohydrate fractions, in vitro rumen degradability and energy value. As plant maturity advanced from stage 1 to 3, the following changes were n...

Evaluation of wheat or corn dried distillers’ grains with solubles on performance and carcass characteristics of feedlot steers

A study was conducted on crossbred steers (n = 275; 376 ± 24 kg) to evaluate performance and carcass quality of cattle fed wheat or corn dried distillers’ grains with solubles (DDGS). The control ration contained 86.6% rolled barley grain, 5.7% supplement and 7.7% barley silage (DM basis). The four treatments included replacement of barley grain at 20 or 40% of the diet (DM basis) with wheat or corn DDGS. Steers were slaughtered at a common end weight of 645 kg with 100 steers randomly (n = 20 per treatment) selected for determination of the retail yield of sub-primal boneless boxed beef (SPBBB). Data were analyzed as a completely randomized design using pen as the experimental unit. Feeding increasing levels of wheat DDGS led to a quadratic increase in dry matter intake (DMI) (P < 0.01), whereas increasing levels of corn DDGS led to a quadratic decrease in DMI (P = 0.01). Average daily gain was not influenced (P = 0.13) by feeding wheat or corn DDGS, but cattle fed corn DDGS exhibited a quadratic increas...

Ultrastructural-chemical makeup of yellow-seeded (Brassica rapa) and brown-seeded (Brassica napus) canola within cellular dimensions, explored with synchrotron reflection FTIR microspectroscopy

Synchrotron-based FTIR micro spectroscopy, developed recently as a novel, rapid and non-destructive analytical technique, could reveal chemical information of the intrinsic microstructures of biological tissues at ultra-spatial resolution. The objective of this study was to use synchrotron reflection FTIR microspectroscopy to explore chemical makeup (functional group and bonding characteristics) of ultrastructural tissues within cellular dimensions (10 µm × 10 µm) of yellow-seeded (Brassica rapa ‘Klondike’) and brown-seeded (Brassica napus ‘Bounty’) canola. The results showed that the ratios of total CH2:CH3, CH3-asymmetric:CH3-symmetric, CH2-asymmetric:CH2-symmetric and total CH-asymmetric:CH-symmetric were 1.06 and 1.13, 1.28 and 1.26, 2.90 and 3.08, 1.82 and 1.78, for the yellow-seeded and brown-seeded canola, respectively. There were no differences between the two canola types in the content and ratios of CH groups (CH2 and CH3) of the scanned areas, indicating that lipid chain length and branching ar...