Ask the Vet

Ear Tag Placement

(Karl Wolfshohl)

READER: I am really confused about 840 ear tags. Is there a difference between 840 and 840 RFID tags? Are there any rules on placement of 840 EID button ear tags? Are these tags considered official identification for proof of brucellosis vaccination?

DR. McMILLAN: When we talk about 840 tags, we are referring to the new standard for animal identification and the effort to improve animal traceability. The number "840" is code for the United States. After the 840, these tags will have 12 other numbers which are unique to that animal.

The term "RFID" refers to radio-frequency identification, telling us that those are tags that can be read with a special scanner. These scanners are becoming more common because they make it easier and more efficient to manage, track and identify our animals. A RFID tag can be an all-in-one tag with an 840 number, where the RFID component allows for scanning to show the number printed on the tag.

The 840 tag doesn't have to be an electronic RFID tag. The 840 tag can simply be a visual, or bangle, ear tag. These are official identification for cattle in all states. They look like traditional ear tags, but they are imprinted with that unique number, which is linked to the animal and the premise (farm or ranch).

These visual tags can be paired with separate RFID button tags. So, producers can apply visual tags with whatever identifying numbers they choose or that are already in the ear, and then link that number back to the official 840 number.

The new official brucellosis identification is an orange RFID button. These are placed in the right ear by the herd veterinarian at the time of vaccination. An official tattoo is placed in the right ear between the middle two cartilage ribs. This tattoo begins with "R" for reduced dose and is followed by the official USDA shield with a "V" in the center and the last number of the year the calf was vaccinated. The USDA prefers producers apply ear tags in the left ear, leaving the right ear for official use.

All ear tags should be placed two-thirds of the way from the outside edge of the ear and one-third of the way from the head between the middle two cartilage ribs.

If a visual tag and an EID button are placed in the ear, the EID button should be placed in this location, with the visual tag a little closer to the outside of the ear. The female (thicker) portion of the tag should always be to the inside of the ear. The male portion (the part that fits over the pin) should always be on the outside. Placement of the button deep in the ear is not recommended.

Go to the USDA Animal and Plant Health Inspection Service page on "Brucellosis" for more information on proper identification:…

READER: We have a cow that turned up lame on one of her front feet. When we got her up, we noticed a large growth between her claws that was infected. It did not look like foot rot. We gave her long-acting tetracycline, and she got better for a while, but now she is lame again. What do we need to do for her, and do you have any thoughts about what this might be?

DR. McMILLAN: This sounds like what is commonly called a corn or interdigital fibroma. It may have started as foot rot, but some chronic irritation has led to an overgrowth of tissue between the claws. Often, this can be from exposure to muddy, contaminated areas or from hard, rocky ground or stubble.

Cattle with poor conformation (especially hoof conformation) or those that are overconditioned or heavy may be more likely to develop interdigital fibromas. Where the toes tend to splay out, we see long hooves trap more manure between the toes. This seems to be most common in the rear legs, and I have seen it more in bulls than in cows.

While small fibromas that do not cause problems may require no treatment, large ones that are infected may need to be surgically removed. This surgery is best done with the animal on its side on a table or under anesthesia, so the veterinarian can clearly see the area and avoid cutting important ligaments that could make the problem worse.

After removal, your veterinarian will often wire the claws together to remove pressure on the surgery site. The wound will be bandaged, and it may have to be changed several times. Healing time can range from one week to several weeks, during which the animal must be kept in a clean, dry environment until the bandages are removed.

Prevention should focus on good hygiene and hoof care. Fibromas from poor conformation will often come back. There is evidence that these may be heritable. If this is suspected, these cattle should be culled or used only in terminal crosses. Bulls should almost always be culled since problems in their calves may not show up for years after the bull is gone.


A Georgia reader writes: As a follow-up to your October column on founder (laminitis) in donkeys, I would like to share that we use grazing muzzles on the donkeys we keep in our cow herd. When a donkey is a guard animal, it always has to be in the good grass with the cows, which can make it more likely to founder. Our donkey wears a grazing muzzle 24/7 and has for several years. It has kept them healthy.


-- Please contact your veterinarian with questions pertaining to the health of your herd. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice but is purely for informational purposes.

-- Write Dr. Ken McMillan at Ask The Vet, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email


Past Issues