What’s that Thing? – Ear Tags

Driving past a pasture you see cattle grazing in the distance. You notice that each animal has something colorful hanging from one or both ears. Wait a minute. Do cows wear earrings?

Yes—sort of. Cattle and other livestock including goats and sheep commonly wear ear tags. These colorful plastic tags are used as a way to identify each animal.

Tag color, location in left or right ear, numbers, and letters work like a code. Based on the code, the farmer can quickly tell important information about an animal, such as:

  • Year of birth
  • Individual identification number or name
  • Sex (bull or heifer)
  • Place of birth

Farmers develop a tag system that works best for their farm.

Cracking the EAR TAG Code

As you can tell from her tag, “Ruby” is the name of this beef calf. On this farm, purple or pink ID tags are used for heifer calves, and blue for bull calves. The octagonal yellow tag is a fly repellent tag.


On this beef feedlot, the cattle are tagged based on the results of an ultrasound. The ultrasound measures backfat and marbling. Each tag color indicates the optimal time to ship the animals to market. The yellow ear tags on these animals mean they will be ready to ship at the same time.


Heifers and cows on this dairy farm are tagged with the last four digits of their 15-digit RFID (radio frequency ID) number. The RFID, or electronic ID, is a button-shaped tag (not visible in this photo) placed inside the ear. RFID tags can be scanned with a special reader. Each animal has a unique RFID number, which allows the farmer to keep computerized records of her milk production. This cow’s tag also includes her name, “Kiwi.”