Impact of high-concentrate feeding and low ruminal pH on methanogens and protozoa in the rumen of dairy cows.
ABSTRACT Non-lactating dairy cattle were transitioned to a high-concentrate diet to investigate the effect of ruminal pH suppression, commonly found in dairy cattle, on the density, diversity, and community structure of rumen methanogens, as well as the density of rumen protozoa. Four ruminally cannulated cows were fed a hay diet and transitioned to a 65% grain and 35% hay diet. The cattle were maintained on an high-concentrate diet for 3 weeks before the transition back to an hay diet, which was fed for an additional 3 weeks. Rumen fluid and solids and fecal samples were obtained prior to feeding during weeks 0 (hay), 1, and 3 (high-concentrate), and 4 and 6 (hay). Subacute ruminal acidosis was induced during week 1. During week 3 of the experiment, there was a significant increase in the number of protozoa present in the rumen fluid (P=0.049) and rumen solids (P=0.004), and a significant reduction in protozoa in the rumen fluid in week 6 (P=0.003). No significant effect of diet on density of rumen methanogens was found in any samples, as determined by real-time PCR. Clone libraries were constructed for weeks 0, 3, and 6, and the methanogen diversity of week 3 was found to differ from week 6. Week 3 was also found to have a significantly altered methanogen community structure, compared to the other weeks. Twenty-two unique 16S rRNA phylotypes were identified, three of which were found only during high-concentrate feeding, three were found during both phases of hay feeding, and seven were found in all three clone libraries. The genus Methanobrevibacter comprised 99% of the clones present. The rumen fluid at weeks 0, 3, and 6 of all the animals was found to contain a type A protozoal population. Ultimately, high-concentrate feeding did not significantly affect the density of rumen methanogens, but did alter methanogen diversity and community structure, as well as protozoal density within the rumen of nonlactating dairy cattle. Therefore, it may be necessary to monitor the rumen methanogen and protozoal communities of dairy cattle susceptible to depressed pH when methane abatement strategies are being investigated.
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ABSTRACT: Methane emissions from ruminants are a significant contributor to global greenhouse gas production. The aim of this study was to examine the effect of diet on microbial communities in the rumen of steers. The effects of dietary alteration (50 : 50 vs 90 : 10 concentrate-forage ratio, and inclusion of soya oil) on methanogenic and bacterial communities in the rumen of steers were examined using molecular fingerprinting techniques (T-RFLP and automated ribosomal intergenic spacer analysis) and real-time PCR. Bacterial diversity was greatly affected by diet, whereas methanogen diversity was not. However, methanogen abundance was significantly reduced (P = 0.009) in high concentrate-forage diets and in the presence of soya oil (6%). In a parallel study, reduced methane emissions were observed with these diets. The greater effect of dietary alteration on bacterial community in the rumen compared with the methanogen community may reflect the impact of substrate availability on the rumen bacterial community. This resulted in altered rumen volatile fatty acid profiles and had a downstream effect on methanogen abundance, but not diversity. Understanding how rumen microbial communities contribute to methane production and how these microbes are influenced by diet is essential for the rational design of methane mitigation strategies from livestock.Journal of Applied Microbiology 09/2011; 111(6):1426-35. · 2.20 Impact Factor
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ABSTRACT: Methanogenic community structure, methane production (CH(4)), and volatile fatty acid (VFA) profiles were investigated in Swedish dairy cows fed a diet with a forage/concentrate ratio of 500/500 or 900/100 g/kg of dry matter (DM) of total DM intake (DMI). The rumen methanogenic population was evaluated using terminal restriction fragment length polymorphism (T-RFLP) analysis, 16S rRNA gene libraries, and quantitative real-time PCR (qRT-PCR). Mean CH(4) yields did not differ (P > 0.05) between diets, being 16.9 and 20.2 g/kg DMI for the 500/500 and 900/100 diets, respectively. The T-RFLP analysis revealed that populations differed between individual cows and that each individual population responded differently to the diets. The 16S rRNA gene libraries revealed that Methanobrevibacter spp. dominated for both diets. CH(4) production was positively correlated with a dominance of sequences representing T-RFs related to Methanobrevibacter thaueri, Methanobrevibacter millerae, and Methanobrevibacter smithii relative to Methanobrevibacter ruminantium and Methanobrevibacter olleyae. Total numbers of methanogens and total numbers of Methanobacteriales were significantly higher with the 500/500 diet (P < 0.0004 and P < 0.002, respectively). However, no relationship was found between CH(4) production and total number of methanogens. No differences were seen in total VFA, propionic acid, or acetic acid contents, but the molar proportion of butyric acid in the rumen was higher for the 500/500 diet than for the 900/100 diet (P < 0.05). Interestingly, the results also revealed that a division of the identified methanogenic species into two groups, suggested in the work of King et al. (E. E. King, R. P. Smith, B. St-Pierre, and A. D. G. Wright, Appl. Environ. Microbiol. 77:5682-5687, 2011), increased the understanding of the variation in CH(4) production between different cows.Applied and Environmental Microbiology 06/2012; 78(17):6172-9. · 3.95 Impact Factor
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ABSTRACT: The ruminal microbial community is a unique source of enzymes that underpin the conversion of cellulosic biomass. In this study, the microbial consortia adherent on solid digesta in the rumen of Jersey cattle were subjected to an activity-based metagenomic study to explore the genetic diversity of carbohydrolytic enzymes in Jersey cows, with a particular focus on cellulases and xylanases. Pyrosequencing and bioinformatic analyses of 120 carbohydrate-active fosmids identified genes encoding 575 putative Carbohydrate-Active Enzymes (CAZymes) and proteins putatively related to transcriptional regulation, transporters, and signal transduction coupled with polysaccharide degradation and metabolism. Most of these genes shared little similarity to sequences archived in databases. Genes that were predicted to encode glycoside hydrolases (GH) involved in xylan and cellulose hydrolysis (e.g., GH3, 5, 9, 10, 39 and 43) were well represented. A new subfamily (S-8) of GH5 was identified from contigs assigned to Firmicutes. These subfamilies of GH5 proteins also showed significant phylum-dependent distribution. A number of polysaccharide utilization loci (PULs) were found, and two of them contained genes encoding Sus-like proteins and cellulases that have not been reported in previous metagenomic studies of samples from the rumens of cows or other herbivores. Comparison with the large metagenomic datasets previously reported of other ruminant species (or cattle breeds) and wallabies showed that the rumen microbiome of Jersey cows might contain differing CAZymes. Future studies are needed to further explore how host genetics and diets affect the diversity and distribution of CAZymes and utilization of plant cell wall materials.PLoS ONE 01/2013; 8(11):e78507. · 3.53 Impact Factor