METAGENOMIC ASSESSMENT OF FEED EFFICIENCY, METHANE PRODUCTION AND METABOLIC POTENTIAL OF COWS

GIZZI, F; ESPARIZ, M; TORRES-MANNO, M; MAGNI, C; MARTÍN, M; BLANCATO, V

Congreso; LVI SAIB (SAIBSAMIGE2020); 2020

Ruminantsare particularly interesting due to their ability to convert human-indigestibleplant biomass into high-quality products for human consumption such as meat andmilk. Ruminants live in a symbiotic relationship with their rumen microbiota,which produces enzymes able to digest their food by breaking down complexpolysaccharides of the plant biomass into volatile fatty acids, microbialproteins, and vitamins. Thus, the rumen microbiota fermentation profile has asignificant influence on the feed conversion efficiency of the host.Metagenomic data of regional rumensamples of young (Y, less than one year old) or adult (A, 2.5 years)cows, feed with grass (P) or alfalfa plus balanced rations (R) wasinvestigated. The potential of lignocellulose breakdown was assessed byidentifying putative carbohydrate-active gene sequences. After searchingagainst the complete CAZy database 83 Glycoside Hydrolase (GH), 28Carbohydrate-Binding Module (CBM), 10 Polysaccharide Lyase (PL), 13 CarbohydrateEsterase (CE), 29 Glycosyl Transferase (GT), and one Auxiliary Activities (AA)families were found present in the samples. The dominant CBM families were CBM6(cellulose binding) and 67 (L-rhamnose binding); then CBM32 (galactose andlactose binding), 35 (xylan binding), 50 (chitin binding) and 20 (starchbinding) were the following more abundant. The most abundant GH was theoligosaccharide degrading enzymes (66%), debranching enzymes were the secondmore abundant (14%), followed by endo-hemicellulases (11%), cellulases (6.5%),and finally xyloglucanases (1.8%). The more abundant families found were GH43,GH3, and GH13 that belong to the oligosaccharide degrading enzymes category,followed by GH5 and GH25 families that encode cellulases and debranchingenzymes, respectively. Methane has a large impact on global warming, it is anend product of anaerobic microbial fermentation in the rumen and it hassignificant negative economic and environmental impacts on animal production.In this context, we analyzed the presence of microbial biomarkers of methaneemissions, from 37 genes reported to predict methane emissions 27 were found inthe YP1 sample, 35 in AP4 and AR5, and 36 in YR2 samples. The most abundant ofthese were genes associated with hydrogenase activity, such as formate andgluconate dehydrogenase, energy synthesis, and heterodisulfide reductase. Feedefficiency is often assessed as either feed conversion ratio (FCR) or residualfeed intake (RFI), low values are associated with efficient animals. Genesassociated with low FCR values are more abundant than genes related to moreinefficient animals in the AP4, AR5, and YP1 samples. On the other hand, nodifference was found in the abundance of RFI related genes. The analysis ofgenetic biomarkers described in this work can be of great significance topredict traits (that usually are difficult to measure), with the aim to improveanimal production, health dietary intervention, or animal breeding.