331 Investigating the Ruminal Metagenome of Grass and Forage-Fed Bison to Uncover Metabolic Activities That Impact the Efficiency of Plant Fiber Utilization

Abstract

Abstract The ability of bison to thrive on grass and forage-based diets is of great interest for the bison industry. However, raising bison on pasture presents challenges, including longer finishing times. While some producers overcome this by feeding grain or concentrate to bison, this practice conflicts with the concept of natural production. Considering that bison maintain better on feed of poor quality compared with domesticated grazers, it can be inferred that there is great potential for improving their productivity on pastures. Because ruminants rely on symbiotic microorganisms to break down and ferment plant polysaccharides into nutrients they can absorb and assimilate, the metabolic capabilities of rumen microbial communities in bison would likely have an important role in contributing to the efficiency of their host. To gain further insight, we investigated the ruminal metagenome of six grass-fed bison. Raw sequence reads generated using an Illumina Miseq (2x250) platform from ruminal microbial genomic DNA were assembled into genomic contigs using custom written Perl scripts. A total of 6,297 contigs, representing a combined total length of 23,822,104 nucleotides, were obtained for all samples. Coding sequences were identified and annotated using RAST (Rapid Annotation using Subsystem Technology), which was followed by assignment to metabolic pathways using references from KEGG (Kyoto Encyclopedia of Genes and Genomes), with a particular focus on carbohydrate metabolism and amino acid synthesis. This analysis resulted in the identification of nine of the ten enzymes necessary for glycolysis, indicating the capacity to metabolize glucose into pyruvate. Two outcomes were predicted for pyruvate: conversion to lactate through lactate dehydrogenases (EC 1.1.1.27, EC 1.1.1.28), as well as the production of acetate through the sequential activity of pyruvate-flavodoxin oxidoreductase (EC 1.2.7.1), phosphate acetyltransferase (EC 2.3.1.8), and acetate kinase (EC 2.7.2.1). Propionate and butyrate were also predicted as end-products being produced in bison rumen, as well as synthesis of precursors for aromatic amino synthesis through the Chorismate-Shikimate pathway. In addition, enzymes involved in the fermentation of five-carbon sugars, such as arabinose (EC 5.1.3.4, EC 2.7.1.16, and EC 5.3.1.4) and xylose (EC 2.7.1.17 and EC 5.3.1.5), were also identified. Characterization of the metabolic potential of ruminal bacteria from pasture-fed bison, such as the utilization of glucose and pentose sugars that form the backbone of structural polysaccharides to produce short chain fatty acids and essential amino acids, will provide further insight on the use of forage and grass-based diets by these animals.