METABOLOMIC ANALYSIS OF BUFFALO FAECES TO IDENTIFY ESTRUS AND EARLY PREGNANCY BIOMARKERS
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Date
2019
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ICAR-NDRI, KARNAL
Abstract
Faeces play significant roles in chemical communication in many animal species.
Faeces is believed as good non-invasive medium for various diagnostic
purposes. In the present study, a comprehensive metabolomics and
metagenomic analysis of buffalo faeces during the estrous cycle and early
pregnancy was studied. Results showed total three bacterial phyla with six
different bacterial order having twenty-four different genera were identified during
the estrous cycle. In addition, the Clostridiales were found to be most abundant
at estrus while the Bacteroidales were encountered exclusively at estrus.
Pathway enrichment analyses showed that steroid biosynthesis and
steroidogenesis were most enriched metabolic pathways at estrus. Testosterone
propionate, 17-alpha-methyltestosterone, hydrocortisone acetate, cortisone,
corticosteroid ester, testosterone cypinate, pregneninolone, aldosterone,
carticosteron, glucocortocoids, testosterone enanthate, cholesterol benzoate and
cholesterone were most predominant metabolites during estrous cycle with
higher abundance intensity at estrus. Based on the above interpretation, it has
been postulated that the cycling dairy animals have a close relationship between
steroid metabolites and members of order Clostridiales and Bacteroidales.
Unfortunately, we did not further validate the individual steroid(s) and/or
metabolites in the faeces. Thus, it is difficult to establish a direct link between
faecal steroid hormone metabolites and faecal bacteria during the estrous cycle.
In addition, 9 metabolites like Pseudoephedrine, 2,5,8,11,14,17-
Hexaoxaoctadecane, 1,3-Dioxolane, 2-heptyl-, Silane, (bromomethyl)trimethyl-,
Benzaldehyde, 3-(4-methoxyphenoxy)-, Benzene, 1-bromo-2-fluoro-, Juglone, 4-
t-Butyl-O-xylene, and 1-Naphthalenamine, N-phenyl- were identified exclusively
at estrus only. However, the direct role of these metabolites in estrus in not yet
known. Total five bacterial phyla with nine different bacterial order having thirtyeight
different genera were identified during early pregnancy in buffalos. The
phylum Firmicutes were found to be common and most abundant in both
pregnant and non-pregnant animals. The proportion of order Clostridiales was
found to be higher in pregnant animals than the non-pregnant, while the order
Acholeplasmatales, Erysipelotrichales and Rhizobiales was exclusively present
in pregnant animal. Interestingly, the free fatty acids were found to be high in
pregnant animal in compare to non-pregnant. Metabolomic data also showed
that the fatty acid biosynthesis and glycerosphingolipid biosynthesis pathways
were highly enriched in pregnant animals. Hexadecanoic acid, Dodecanoic acid,
Tetradecanoic acid, undecanoic acid, nonadecanoic acid, octadecanoic acid,
pentadecanoic acid and tridecanoic acid were highly abundant in pregnant
buffaloes. These differentially abundant free fatty acids could be the potential
biomarker for early pregnancy. In conclusion, the results of present study
demonstrated that shift in faecal metabolome and bacterial profile during the
estrous cycle and early pregnancy showed a strong relationship amongst the gut
microbiome, faecal metabolome and animal reproductive physiology.