Rumen bolus tag
Animal identification
What is it?
A rumen bolus is a ceramic RFID transponder shaped like a large capsule (about 70 × 20 mm) that is orally administered to cattle and sheep. It drops into the reticulum (the second stomach chamber) and stays there permanently, held in place by its weight and by the ridged stomach lining. Bolus tags are the most tamper-proof livestock identification method – they cannot be lost, torn out, or transferred.
How it works
The transponder is encapsulated in a dense ceramic body (specific gravity ~3) heavy enough to remain in the reticulum against stomach contractions. It is administered using a bolus gun (a specialised oral applicator). The ceramic housing resists stomach acid and mechanical abrasion. A reader held near the animal's left side (where the reticulum sits) can read the tag through the body wall.
Use cases
- Cattle identification in countries requiring tamper-proof ID
- Sheep and goat identification
- Dairy cattle management
- Breeding programmes
- Disease traceability (BSE, foot-and-mouth)
Pros
- Impossible to lose or tamper with
- No visible external tag to damage
- Lasts the lifetime of the animal
- No ear trauma or infection risk
- Conforms to ISO 11784/11785
Cons
- Requires skilled administration
- Cannot be visually matched to the animal (no visible tag)
- Read range limited by body tissue (20–40 cm)
- Higher cost than ear tags
- Cannot be retrieved or reused
Specifications
| Power type | Passive – powered by reader signal |
|---|---|
| Frequency | LF (134.2 kHz, ISO 11784/11785) |
| Read range | Up to 40 cm through the animal |
| Lifespan | Lifetime of the animal |
| Price range | $3–$10 per unit |
| Environmental rating | Designed for permanent gastric environment |