The structural and functional capacity of ruminal and cecal microbiota in growing cattle was unaffected by dietary supplementation of linseed oil and nitrate
Abstract
Microorganisms in the digestive tract of ruminants differ i
n their functionality and ability
to use feed constituents. While cecal microbiota play an impo
rtant role in post-rumen
fermentation of residual substrates undigested in the rume
n, limited knowledge exists
regarding its structure and function. In this trial we inves
tigated the effect of dietary
supplementation with linseed oil and nitrate on methane emi
ssions and on the structure
of ruminal and cecal microbiota of growing bulls. Animals we
re allocated to either a
CTL (control) or LINNIT (CTL supplemented with 1.9% linseed
and 1.0% nitrates) diet.
Methane emissions were measured using the GreenFeed system
. Microbial diversity was
assessed using amplicon sequencing of microbial genomic DN
A. Additionally, total RNA
was extracted from ruminal contents and functional
mcrA
and
mtt
genes were targeted
in amplicon sequencing approach to explore the diversity of
functional gene expression
in methanogens. LINNIT had no effect on methane yield (g/kg D
MI) even though it
decreased methane production by 9% (g/day;
P
<
0.05).
Methanobrevibacter-
and
Methanomassiliicoccaceae
-related OTUs were more abundant in cecum (72 and 24%)
compared to rumen (60 and 11%) irrespective of the diet (
P
<
0.05). Feeding LINNIT
reduced the relative abundance of
Methanomassiliicoccaceae mcrA
cDNA reads in
the rumen. Principal component analysis revealed significa
nt differences in taxonomic
composition and abundance of bacterial communities betwee
n rumen and cecum.
Treatment decreased the relative abundance of a few
Ruminococcaceae
genera, without
affecting global bacterial community structure. Our resea
rch confirms a high level of
heterogeneity in species composition of microbial consort
ia in the main gastrointestinal
compartments where feed is fermented in ruminants. There wa
s a parallel between the
lack of effect of LINNIT on ruminal and cecal microbial commu
nity structure and functions differences in Rumen and Cecum Microbiomes
on one side and methane emission changes on the other. These re
sults suggest that
the sequencing strategy used here to study microbial diversity and function accurately
reflected the absence of effect on methane phenotypes in bulls treated with linseed plus
nitrate.
Domains
Life Sciences [q-bio]
Origin : Publisher files allowed on an open archive
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