RUMEN METAGENOME PROFILES AND METHANE EMISSION LEVELS IN VECHUR AND CROSSBRED CATTLE UNDER DIFFERENT DIETARY REGIMENS
Loading...
Date
2018
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
COLLEGE OF VETERINARY AND ANIMAL SCIENCES-MANNUTHY,THRISSUR
Abstract
A study was conducted to assess the rumen metagenome profiles and
methane emission levels in Vechur and crossbred cattle under different dietary
regimens. Feeding patterns were designed to have an increasing proportion of
forage and a decreasing proportion of the concentrate mix. A total of ten adult
cows comprising five in each genetic group maintained on standard ration
(Forage: concentrate ratio of 50:50) formed the material for the whole
metagenomic study. Out of twelve adult cows, six adult cows each of Vechur and
crossbred cattle fed with forage: concentrate ratio of 75:25 and 100:0 for a period
of three weeks were selected as the experimental animals for 16S rRNA based
metagenome study. Rumen liquor and rumen gas samples were collected from all
the experimental animals. DNA samples isolated from rumen liquor using
standard procedure were pooled genetic group wise and subjected to metagenome
sequencing using Illumina HiSeq 2500 platform and further bioinformatics
analysis. The concentrations of methane (per cent) in the gas samples were
determined using a methane analyser.
Research findings from whole metagenomic study revealed that bacteria
followed by Archaea and Eukaryota dominated in the Vechur as well as the
crossbred rumen samples. In Vechur and crossbred cattle rumen, 1086 and 1262
microbial species were observed exclusively and 4731 species were shared
between habitats. There was a significant difference in total microbial species
abundance between two genetic groups. Diversity indices displayed a higher
microbial diversity in Vechur cows compared to crossbred cows and also there
was a significant difference in diversity between genetic groups. Functional
annotation of contigs carried out by SEED classification revealed sequence reads
related to carbohydrate and protein metabolism were the most abundant in rumen
of both genetic groups. A significant difference in genes associated with different
metabolic pathway as revealed by KEGG pathway analysis was found between
two genetic groups.
The 16S rRNA based metagenome sequencing study showed that
Bacteroidetes and Firmicutes were the predominant phyla in both genetic groups.
An increase in the Firmicutes to Bacteroidetes ratio observed with the increase in
roughage proportion. There was highly significant difference in bacterial diversity
indices and no significant difference in total bacterial phylum abundance between
diets and genetic groups. Comparison of methane emission levels in Vechur and
crossbred cattle under different diets confirmed the effect of genetic group and
diet on methane emission levels. Significantly higher methane emission levels
were observed for Vechur cattle and 100 per cent forage dietary regimen in both
genetic groups.