J Dairy Sci. 2017 Apr 5. pii: S0022-0302(17)30285-0. doi: 10.3168/jds.2016-11473. [Epub ahead of print]
- 1
- Department of Animal Biosciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada. Electronic address: oalzahal@gmail.com.
- 2
- Department of Agriculture, Food and Nutritional Science, University of Alberta, Edmonton T6G 2P5, Canada.
- 3
- AB Vista, Marlborough, SN8 4AN, UK.
- 4
- Department of Animal Biosciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
Abstract
The
objective of the current study was to employ a DNA-based sequencing
technology to study the effect of active dry yeast (ADY)
supplementation, diet type, and sample location within the rumen on
rumen bacterial community diversity and composition, and to use an
RNA-based method to study the effect of ADY supplementation on rumen
microbial metabolism during high-grain feeding (HG). Our previous report
demonstrated that the supplementation of lactating dairy
cows with ADY attenuated the effect of subacute ruminal acidosis.
Therefore, we used samples from that study, where 16 multiparous,
rumen-cannulated lactating Holstein cows were randomly assigned to 1 of 2
dietary treatments: ADY (Saccharomyces cerevisiae strain Y1242, 80
billion cfu/animal per day) or control (carrier only). Cows received a
high-forage diet (77:23, forage:concentrate), then were abruptly
switched to HG (49:51, forage:concentrate). Rumen bacterial community
diversity and structure were highly influenced by diet and sampling
location (fluid, solids, epimural). The transition to HG reduced
bacterial diversity, but epimural bacteria maintained a greater
diversity than fluid and solids. Analysis of molecular variance
indicated a significant separation due to diet × sampling location, but
not due to treatment. Across all samples, the analysis yielded 6,254
nonsingleton operational taxonomic units (OTU), which were classified
into several phyla: mainly Firmicutes, Bacteroidetes, Fibrobacteres,
Tenericutes, and Proteobacteria. High forage and solids were dominated
by OTU from Fibrobacter, whereas HG and fluid were dominated by OTU from
Prevotella. Epimural samples, however, were dominated in part by
Campylobacter. Active dry yeast had no effect on bacterial community
diversity or structure. The phylum SR1 was more abundant in all ADY
samples regardless of diet or sampling location. Furthermore, on HG,
OTU2 and OTU3 (both classified into Fibrobacter succinogenes) were more
abundant with ADY in fluid and solids than control samples. This
increase with ADY was paralleled by a reduction in prominent Prevotella
OTU. Metatranscriptomic profiling of rumen microbiome conducted on
random samples from the HG phase showed that ADY increased the abundance
of the cellulase endo-β-1,4-glucanase and had a tendency to increase
the hemicellulase α-glucuronidase. In conclusion, the shift from high
forage to HG and sampling location had a more significant influence on
ruminal bacterial community abundance and structure compared with ADY.
However, evidence suggested that ADY can increase the abundance of some
dominant anaerobic OTU belonging to F. succinogenes and phylum SR1.
Further, microbial mRNA-based evidence suggested that ADY can increase
the abundance of a specific microbial fibrolytic enzymes.
The Authors. Published by the Federation of Animal Science Societies and Elsevier Inc. on behalf of the American Dairy
Science Association®. This is an open access article under the CC
BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).
KEYWORDS:
active dry yeast; dairy cow; metatranscriptome; rumen microbiome; subacute ruminal acidosis
