Rumen Microbial Predictors for Short-Chain Fatty Acid Levels and the Grass-Fed Regimen in Angus Cattle

Jianan Liu; Ying Bai; Fang Liu; Richard A Kohn; Daniel A Tadesse; Saul Sarria; Robert W Li; Jiuzhou Song

doi:10.3390/ani12212995

Rumen Microbial Predictors for Short-Chain Fatty Acid Levels and the Grass-Fed Regimen in Angus Cattle

Animals (Basel). 2022 Oct 31;12(21):2995. doi: 10.3390/ani12212995.

Authors

Jianan Liu¹, Ying Bai², Fang Liu³, Richard A Kohn¹, Daniel A Tadesse⁴, Saul Sarria⁴, Robert W Li⁵, Jiuzhou Song¹

Affiliations

¹ Department of Animal & Avian Sciences, University of Maryland, College Park, MD 20742, USA.
² College of Life Sciences and Food Engineering, Hebei University of Engineering, Handan 056038, China.
³ College of Public Health, Zhengzhou University, Zhengzhou 450001, China.
⁴ Food and Drug Administration, Center for Veterinary Medicine, Office of Research, Laurel, MD 20708, USA.
⁵ United States Department of Agriculture, Agriculture Research Service, Animal Genomics and Improvement Laboratory, Beltsville, MD 20705, USA.

Abstract

The health benefits of grass-fed beef are well documented. However, the rumen microbiome features in beef steers raised in a grass-fed regimen have yet to be identified. This study examined the rumen microbiome profile in the feeding regimes. Our findings show that the rumen microbiome of the grass-fed cattle demonstrated greater species diversity and harbored significantly higher microbial alpha diversity, including multiple species richness and evenness indices, than the grain-fed cattle. Global network analysis unveiled that grass-fed cattle's rumen microbial interaction networks had higher modularity, suggesting a more resilient and stable microbial community under this feeding regimen. Using the analysis of compositions of microbiomes with a bias correction (ANCOM-BC) algorithm, the abundance of multiple unclassified genera, such as those belonging to Planctomycetes, LD1-PB3, SR1, Lachnospira, and Sutterella, were significantly enriched in the rumen of grass-fed steers. Sutterella was also the critical genus able to distinguish the two feeding regimens by Random Forest. A rumen microbial predictor consisting of an unclassified genus in the candidate division SR1 (numerator) and an unclassified genus in the order Bacteroidales (denominator) accurately distinguished the two feeding schemes. Multiple microbial signatures or balances strongly correlated with various levels of SCFA in the rumen. For example, a balance represented by the log abundance ratio of Sutterella to Desulfovibrio was strongly associated with acetate-to-propionate proportions in the rumen (R² = 0.87), which could be developed as a valuable biomarker for optimizing milk fat yield and cattle growth. Therefore, our findings provided novel insights into microbial interactions in the rumen under different feed schemes and their ecophysiological implications. These findings will help to develop rumen manipulation strategies to improve feed conversion ratios and average daily weight gains for grass- or pasture-fed cattle production.

Keywords: Angus cattle; grain-fed beef; grass-fed beef; microbiome; rumen; short-chain fatty acids.

Grants and funding

2017/Jorgenson Fund