Cud chewing is the cheapest rumen sensor
Rumination is how the cow rebuilds particle size and pumps saliva bicarbonate into the vat. If she stops, the buffer stops.
3 min read · 2026-09-07
A resting dairy cow that is not heat-stressed should spend a large share of her day ruminating. Each bolus is re-chewed, mixed with saliva, and sent back. That loop is mechanical — smaller particles for the microbes — and chemical — bicarbonate that keeps rumen pH in the zone fiber digesters need.
Count cows lying or standing quietly after a meal. Many herds use a simple barn walk: a clear majority of resting cows should be chewing. Empty bunks, slug meals, heat, pain, or a ration that cannot hold a fiber mat all cut that number.
This is not a lab test. It is a daily check you can do without a pH bolus. If chewing falls and manure loosens in the same week, open the starch-and-SARA universe next — the same cow, a tighter question.
Keep reading
View the networkNext
Particle size holds the fiber mat
If the TMR is too fine, the forage raft thins — less trapping, less re-chewing, less bicarbonate-rich saliva.
Sister note · 3 min
Home plate: Rumen · Inside the rumen · Rumination & saliva
- Rumination & salivaThe buffer pumpPlaced here
- The sensor is a barn alarm, not a diagnosisRumination and activity collars flag deviations from a cow’s own baseline — useful alarms that still need the cow, bunk, and stall before you act.Sister note
- Saliva is the free bufferBagged bicarbonate has a line item. Saliva is the free, manageable buffer you earn with chewing — not the larger proton sink than SCFA absorption.Same focus
Mark size is the kind. Color is the atlas area.
- Focus
- Field note
- Rumen
Sources
- From Feed to Milk: Understanding Rumen Function — Penn State Extension
- Penn State Particle Separator — Penn State Extension
- Ruminant Digestive System — Merck Veterinary Manual