Athol Klieve

Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed degradation and methane formation by ruminants rely on metabolic interactions between rumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial community composition was determined in 742 samples from 32 animal species and 35 countries, to estimate if this was influenced by diet, host species, or geography. Similar bacteria and archaea dominated in nearly all samples, while protozoal communities were more variable. The dominant bacteria are poorly characterised, but the methanogenic archaea are better known and highly conserved across the world. This universality and limited diversity could make it possible to mitigate methane emissions by developing strategies that target the few dominant methanogens. Differences in microbial community compositions were predominantly attributable to diet, with the host being less influential. There were few strong co-occurrenc...

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Until recently, knowledge of ruminant gut microbiology was primarily obtained using classical culture based techniques, which probably only account for 10 to 20% of the rumen microbial population. New gene-based technologies can now be employed to examine microbial diversity through the use of small sub-unit ribosomal DNA analysis (e.g. 16S rDNA) and to understand the function of complex microbial ecosystems in the rumen through metagenomic analysis. These technologies have the potential to revolutionize the understanding of rumen function and will overcome the limitations of classical based techniques, including isolation and taxonomic identification of strains important to efficient rumen function and better understanding of the roles of microorganisms in relation to achieving high productivity and decreasing environmental pollutants. This book presents a comprehensive up-to-date account of the methodologies and protocols for conventional and modern molecular techniques that are c...

Introduction: Large variation in live weight gain (LWG) occurs in weaners. One aspect that may differ is the association of the microbial population with the LWG. The aim of this experiment was to evaluate the relationship between the ruminal bacterial population and post-weaning LWG by examining (using denaturing gradient gel electrophoresis (DGGE)) rumen bacterial profiles of steers grazing low crude protein (CP) pasture. Methods: Two hundred and three male calves from Lakefield Station, Mataranka, NT, were weighed, marked and weaned in April 2010 and then grazed native pastures as a single mob and were offered a loose lick supplement (10% urea, 26% salt, 15% kynofos, 10% gran-am, 15% copra meal, 20% limestone and 4% trace mineral mix) at approximately 120 g/head/day. Ninety days after weaning the steers were weighed and post-weaning ADG was determined. Thirty six pairs of steers divergent in post-weaning ADG were selected for the pen study by pairing steers with the same weaning ...

ABSTRACT Methane is a potent greenhouse gas with a global warming potential similar to 28 times that of carbon dioxide. Consequently, sources and sinks that influence the concentration of methane in the atmosphere are of great interest. In Australia, agriculture is the primary source of anthropogenic methane emissions (60.4% of national emissions, or 3 260 kt(-1) methane year(-1), between 1990 and 2011), and cropping and grazing soils represent Australia's largest potential terrestrial methane sink. As of 2011, the expansion of agricultural soils, which are similar to 70% less efficient at consuming methane than undisturbed soils, to 59% of Australia's land mass (456 Mha) and increasing livestock densities in northern Australia suggest negative implications for national methane flux. Plant biomass burning does not appear to have long-term negative effects on methane flux unless soils are converted for agricultural purposes. Rice cultivation contributes marginally to national methane emissions and this fluctuates depending on water availability. Significant available research into biological, geochemical and agronomic factors has been pertinent for developing effective methane mitigation strategies. We discuss methane-flux feedback mechanisms in relation to climate change drivers such as temperature, atmospheric carbon dioxide and methane concentrations, precipitation and extreme weather events. Future research should focus on quantifying the role of Australian cropping and grazing soils as methane sinks in the national methane budget, linking biodiversity and activity of methane-cycling microbes to environmental factors, and quantifying how a combination of climate change drivers will affect total methane flux in these systems.

Bacteriophages are ubiquitous to the rumen ecosystem; they have a role in nitrogen metabolism through bacterial lysis in the rumen, they may help to regulate bacterial population densities, be an agent for genetic exchange and be of use in biocontrol of bacterial populations ...

The effect of Leucaena leucocephala inclusion in sheep diets upon rumen function was evaluated. Nine Pelibuey sheep, 32.6 ± 5.33 kg live weight (LW), fitted with rumen cannula were used. A complete randomized block design was employed. Two experimental periods of 60 days each, with 60-day intervals between them, were used. Experimental treatments were as follows (n = 6): T1 (control), 100 % Pennisetum purpureum grass; T2, 20 % L. leucocephala + 80 % P. purpureum; T3, 40 % L. leucocephala + 60 % P. purpureum. In situ rumen neutral detergent fiber (aNDF) and crude protein (CP) degradation, dry matter intake (DMI), volatile fatty acids (VFA) production, estimated methane (CH4) yield, rumen pH, ammonia nitrogen (N-NH3), and protozoa counts were measured. The aNDF in situ rumen degradation of P. purpureum and leucaena was higher (P < 0.05) in T2 and T3. Leucaena CP degradation was higher in T2 and T3 but for P. purpureum it was only significantly higher in T3. Leucaena aNDF and CP degradation rate (c) was 50 % higher (P < 0.05) in T2 and T3, but only higher in T3 for P. purpureum. Voluntary intake and rumen (N-NH3) was higher in T2 and T3 (P = 0.0001, P = 0.005, respectively). Molar VFA proportions were similar for all treatments (P > 0.05). Protozoa counts and in vitro gas production (48 h) were lower in T2 and T3 (P < 0.05, P < 0.0001). Estimated methane yield (mol CH4/day) was higher in sheep fed leucaena (P < 0.0001). However, CH4 yield relative to animal performance (mol CH4/g LW gain) was lower in T2 and T3 (P < 0.0001). In summary, these results indicate that including L. leucocephala in sheep diets did not modify rumen fermentation pattern (same VFA ratios) nor reduce the amount of CH4 per unit of DMI (mol CH4/g DMI). However, leucaena inclusion does increase rumen N-NH3, aNDF and CP digestibility, and voluntary intake.

Kangaroos ferment forage material in an enlarged forestomach analogous to the rumen, but in contrast to ruminants, they produce little or no methane. The objective of this study was to identify the dominant organisms and pathways involved in hydrogenotrophy in the kangaroo forestomach, with the broader aim of understanding how these processes are able to predominate over methanogenesis. Stable isotope analysis of fermentation end products and RNA stable isotope probing (RNA-SIP) were used to investigate the organisms and biochemical pathways involved in the metabolism of hydrogen and carbon dioxide in the kangaroo forestomach. Our results clearly demonstrate that the activity of bacterial reductive acetogens is a key factor in the reduced methane output of kangaroos. In in vitro fermentations, the microbial community of the kangaroo foregut produced very little methane, but produced a significantly greater proportion of acetate derived from carbon dioxide than the microbial community of the bovine rumen. A bacterial operational taxonomic unit closely related to the known reductive acetogen Blautia coccoides was found to be associated with carbon dioxide and hydrogen metabolism in the kangaroo foregut. Other bacterial taxa including members of the genera Prevotella, Oscillibacter and Streptococcus that have not previously been reported as containing hydrogenotrophic organisms were also significantly associated with metabolism of hydrogen and carbon dioxide in the kangaroo forestomach.

ABSTRACT When cattle are fed grain, acidotic ruminal conditions and decreased efficiency in starch utilisation can result from the rapid production and accumulation of lactic acid in the rumen. The efficacy of drenching cattle with Megasphaera elsdenii and Ruminococcus bromii to improve animal performance was investigated. A feedlot trial was undertaken with 80 Bos indicus crossbred steers (initial liveweight 347.1 (s.d. 31.7) kg) in 10 pens in a randomised complete block design. An empty-pen-buffer was maintained between treated (inoculated) and untreated (control) groups to avoid transfer of inoculant bacteria to the control steers. Inoculated steers were orally drenched with M. elsdenii YE34 and R. bromii YE282, and populations increased rapidly over 3–14 days. The steers were fed for a total of 70 days with commercial, barley-based, feedlot rations. High growth rates (1.91 kg per day) were achieved throughout the experiment in both the inoculated and control steers. Intakes averaged 21.3 g dry matter (DM) per kg liveweight per day. There was probably no acidosis achieved in this trial following challenge (i.e. no change in pH occurred). There were no differences in any production or carcass measurements between the control and inoculated steers overall. However, the control group acquired dense ruminal populations of M. elsdenii by Day 14, while R. bromii populations established at high densities within the first 2 weeks but then declined and were undetectable by Day 50. R. bromii appears to be only transiently dominant, and once its dominance waned, it appeared that Ruminobacter spp. established in the rumen. Ruminobacter spp. became dominant between 14 and 28 days in all the steers examined and persisted through to the end of the study. These Ruminobacter spp. may be of future interest in the development of probiotics for grain-fed cattle.

A novel method for screening bacterial isolates for their potential to inhibit the growth of ruminal methanogenic Archaea was developed using a modification of the soft agar overlay technique, formally used for the isolation of lytic bacteriophages. This method may be used in the specific, hydrogen-rich conditions required for the growth of ruminal methanogenic Archaea.