Taxonomic and functional shifts in rumen microbiome of buffalo calves under longterm strategic supplementation of phyto-feed additives

PRAMOD KUMAR SONI¹Anju Kala²Payal Agarwal²Ram Pratim Deka^3,4H Rahman⁴Lakshmi V Kennedy⁴L. C. Chaudhary^2*

• ¹Rani Lakshmi Bai Central Agricultural University, Jhansi, India
• ²ICAR - Indian Veterinary Research Institute, Izatnagar, India
• ³International Livestock Research Institute, Nairobi, Kenya
• ⁴ILRI, South East Asia Office New Delhi India, New Delhi, India

The present study was aimed at understanding a shift in rumen microbiome of buffaloes fed with additive and without additive. To comprehend the process, studies on rumen microbial metagenomics, as well as in vivo and in vitro rumen fermentation, were conducted. Three buffalo male calves were fed at control diets and three fed with additive FAI i.e. a blend of garlic (Allium sativum), ajwain (Trachyspermum ammi), harad (Terminalia chebula) and soapnut (Sapindus mukurossi) in equal proportion and FAII, ajwain oil. Using the same phyto-additives for a long time might let rumen microbes adapt and reduce their effect. So, we changed the additives every 15 days to study how this switching affects microbial response over long time. After 21 d of feeding, rumen liquor was sampled just before 2h post feeding. Dominant bacterial phyla included Prevotella, Bacteroides, Succiniclasticum, Fibrobacter, Clostridium, Alistipes, Ruminococcus and Butyrivibrio, with over 50 bacterial species consistently found across all animals. The main archaeal phylum was Euryarchaeota (>85%), with others like Candidatus_Bathyarchaeota and Thaumarchaeota also present. The 'Not Assigned' group also made up a major share. At the genus level, Methanomicrobium and Methanobrevibacter were most abundant (~30% each), followed by Methanosphaera, Methanosarcina and Methanomassiliicoccus.. Interestingly, while the total abundance of Archaea and Bacteroidota showed no significant differences between the groups, specific bins within these phyla displayed noticeable variations. The study found that phyto feed additives altered the rumen microbiome by reducing methanogens like Methanobrevibacter, enhancing fiber-degrading enzymes and shifting microbial composition leading to lower methane production and improved fiber utilization.