CONICET | Buscador de Institutos y Recursos Humanos

Ruminants are particularly interesting due to their ability to convert human-indigestible plant biomass into high-quality products for human consumption such as meat and milk. Ruminants live in a symbiotic relationship with their rumen microbiota, which produces enzymes able to digest their food by breaking down complex polysaccharides of the plant biomass into volatile fatty acids, microbial proteins, and vitamins. Thus, the rumen microbiota fermentation profile has a significant influence on the feed conversion efficiency of the host. Metagenomic data of regional rumen samples 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) was investigated. The potential of lignocellulose breakdown was assessed by identifying putative carbohydrate-active gene sequences. After searching against the complete CAZy database 83 Glycoside Hydrolase (GH), 28 Carbohydrate-Binding Module (CBM), 10 Polysaccharide Lyase (PL), 13 Carbohydrate Esterase (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 and lactose binding), 35 (xylan binding), 50 (chitin binding) and 20 (starch binding) were the following more abundant. The most abundant GH was the oligosaccharide degrading enzymes (66%), debranching enzymes were the second more 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 debranching enzymes, respectively. Methane has a large impact on global warming, it is an end product of anaerobic microbial fermentation in the rumen and it has significant negative economic and environmental impacts on animal production. In this context, we analyzed the presence of microbial biomarkers of methane emissions, from 37 genes reported to predict methane emissions 27 were found in the YP1 sample, 35 in AP4 and AR5, and 36 in YR2 samples. The most abundant of these were genes associated with hydrogenase activity, such as formate and gluconate dehydrogenase, energy synthesis, and heterodisulfide reductase. Feed efficiency is often assessed as either feed conversion ratio (FCR) or residual feed intake (RFI), low values are associated with efficient animals. Genes associated with low FCR values are more abundant than genes related to more inefficient animals in the AP4, AR5, and YP1 samples. On the other hand, no difference was found in the abundance of RFI related genes. The analysis of genetic biomarkers described in this work can be of great significance to predict traits (that usually are difficult to measure), with the aim to improve animal production, health dietary intervention, or animal breeding.