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Rumen Function: The Good, the Bad, and the Additives.

Stuart Gough
ruminant specialist
Monday 10 Nov 2025

Rumen Balance: The Key to Sustainable Production. Can yeasts, essential oils and buffers be part of this?

Cows are many things: sociable, inquisitive, gentle and sentient, They always add much to your day. But they could also be considered as a transport systems for a living, anaerobic digester which converts feedstuffs into the building blocks for milk, foetal growth and meat production within the animal itself.

The rumen is a highly active anaerobic fermentation ecosystem that converts fibrous feeds into volatile fatty acids (VFAs), microbial protein, and gases. Sustainable dairy production relies on keeping this ecosystem balanced: maintaining robust fibre digestion, stable pH, efficient nitrogen capture, and a healthy rumen epithelium.

The rumen neighborhood: who lives there and why

A healthy rumen contains a vast and interdependent microflora: bacteria (~95% by number), protozoa (3–5%), anaerobic fungi (<1% but highly active), and methanogenic archaea (trace). Each group plays distinct roles in deconstructing plant material, cross-feeding each other , and stabilising fermentation.

Microbial GroupApproximate ProportionPrimary Roles
Bacteria~95%Degrade fibre, starch, sugars, and protein; produce VFAs and microbial biomass
Protozoa3–5%Grazing on bacteria and starch; moderate fermentation rate; contribute to rumen stability
Anaerobic fungi<1%Physically penetrate plant cell walls; initiate fibre disruption
Methanogens (archaea)TraceConsume H₂ to form Methane; regulate redox balance

There are 8 billion people on the earth -

1 cow rumen ≈ population of 100,000–1,000,000 Earths in microbes.

These populations are sensitive to pH, oxygen, substrate supply, and rumen motility, hence the importance of consistent feeding and effective fibre.

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