Assessing the impact of oscillating dietary crude protein on the stability of the rumen microbiome in dairy cattle

Authors: VIQUEZ-UMANA, FIORELLA - University Of Wisconsin; ERICKSON, MARYGRACE - University Of Wisconsin; Young, Juliana; Zanton, Geoffrey; WATTIAUX, MICHEL - University Of Wisconsin; SUEN, GARRET - University Of Wisconsin; MANTOVANI, HILARIO - University Of Wisconsin

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2025
Publication Date: 6/10/2025
Citation: Viquez-Umana, F., Erickson, M., Young, J.D., Zanton, G.I., Wattiaux, M., Suen, G., Mantovani, H. 2025. Assessing the impact of oscillating dietary crude protein on the stability of the rumen microbiome in dairy cattle. Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2025.1568112.
DOI: https://doi.org/10.3389/fmicb.2025.1568112

Interpretive Summary: The symbiotic relationship between mammals and their associated microbiota is essential for maintaining host health and function and these interactions are particularly prominent in ruminants. This trial evaluated the ruminal microbial community composition for cows with feeding patterns where crude protein (CP) content oscillated at 48-h intervals or were static at two median levels of dietary CP (13.8 and 15.5% of dry matter). We found that oscillating diets increased rumen microbial diversity and affected the rumen microbiome composition but was unaffected by dietary CP level. These results are important to dairy farmers, nutritionists, and researchers feeding diets with lower levels of nitrogen by showing that the dairy cow microbiome is resilient to short term oscillation in CP.

Technical Abstract: Understanding how the rumen microbiota respond to varying protein levels and feeding patterns is critical for optimizing dairy cattle nutrition. This study investigated the influence of dietary crude protein (CP) levels (13.8% or 15.5% CP of ration dry matter) and CP feeding patterns (constant over time (static) or oscillating by 1.8 percentage units above and below the mean every 48 hours) on the composition, diversity, and function of the rumen microbiome. Using a replicated Latin Square design, eight rumen-cannulated Holstein cows were assigned each of the four dietary treatments (structured as a 2x2 factorial) in four consecutive 28-day periods (with 24 days of adaptation and 4 days of sampling). Rumen samples were collected four hours post-feeding, and amplicon libraries of the V4 region of the 16S rRNA gene were sequenced and analyzed to assess changes in microbiome composition. Additionally, volatile fatty acids (VFAs) were measured to evaluate rumen microbial function. Results revealed that oscillating diets increased rumen microbial diversity (Shannon index, P = 0.04). The rumen microbiome composition was also affected by CP feeding pattern (P = 0.05), but not by dietary CP level (P = 0.21). Furthermore, differential abundance analysis using ANCOM-BC identified the genera CAG-352 (P = 0.0001) and an unclassified member of the family Acholeplasmataceae (P = 0.0002) as significantly affected by treatment. Last, VFA profiles remained consistent across treatments, with no observable changes in production parameters. These findings support the hypothesis that the rumen microbiome exhibits stability even under substantial variation in ruminal supply of dietary CP, indicating the presence of compensatory mechanisms. These results emphasize the importance of further research into rumen metabolic processes and host-microbiome interactions to unlock new opportunities for enhancing protein nutrition in dairy cattle.