Individuality of ruminal methanogen/protozoa populations in beef cattle fed diets containing dried distillers' grain with solubles

This study investigated the variability of ruminal methanogen/protozoa among beef heifers (n = 4) fed corn- or wheat-dried distillers' grain with solubles (DDGS). Polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis and quantitative real-time PCR were used to investigate variation in ruminal methanogenic communities, while protozoal communities were analyzed using light microscopy. Observed methanogen profiles were not affected by DDGS source, but were distinctive within individuals (Global R=0.87, P < 0.01). Populations of total methanogens, total protozoa, Methanobrevibacter sp. AbM4, Entodinium, and Polyplastron varied among heifers and diets, while densities of total Methanosphaera stadtmanae, Isotricha, and Ostracodinium only differed among individual hosts. Responses in the ruminal methanogenic community to DDGS source were host dependent, suggesting that host biology should not be ignored if dietary strategies are used to alter ruminal methanogens to lower enteric methane emissions.