The most common methods of identifying hogs are ear notching, ear tags, tattoos, and RFID electronic tags. Each method serves a different purpose depending on whether you’re raising purebred breeding stock, commercial market hogs, or show pigs for exhibition. The right choice depends on your operation’s size, your budget, and whether you need to meet specific regulatory requirements for moving animals across state lines or to slaughter.
Ear Notching
Ear notching is the oldest and most widely used identification system in the swine industry. It involves cutting small, V-shaped notches into specific positions along the edge of a pig’s ears using a specialized notching tool. Each notch position corresponds to a number, and the combination of notches creates a unique ID for every animal in the litter. The right ear typically identifies the litter number, while the left ear identifies the individual pig within that litter.
This method is permanent, requires no ongoing maintenance, and costs almost nothing beyond the notching pliers. It’s especially popular among purebred breeders because registry associations recognize ear notching as official identification when it’s recorded in their book of record. The notching is typically done within the first few days of life, when the ear cartilage is still soft and the procedure causes minimal stress. One limitation: you need to be close enough to physically read the notches, and as pigs grow, notches can sometimes become harder to distinguish if they weren’t cut cleanly.
Ear Tags
Ear tags are the most versatile option and are used across all livestock species. For hogs, tags come in plastic or metal and should be placed in the middle third of the ear, between the upper and lower cartilage ribs. Placement matters. Tags applied too far toward the outer edge are prone to snagging on equipment or fencing and can tear out. Tags placed too far toward the base of the ear can pinch the tissue and cause infection or tissue death.
USDA-approved official ear tags are required for many regulatory purposes, including interstate movement of breeding stock and identification of feeder pigs. For slaughter and feeder swine, the ear tag must bear a Premises Identification Number (PIN) assigned by your state animal health official. This PIN links every animal back to the farm where it originated, which is critical for disease traceability. Backtags, which are temporary adhesive tags applied to the animal’s back, are also approved but only for swine already moving through slaughter channels.
Tattoos
Tattooing imprints a number or letter combination into the pig’s skin using indelible ink and a set of sharp character dies. There are two main approaches: ear tattoos applied with plier-style tattoo instruments, and slap tattoos applied to the shoulder or inner flank using a flat “slapper” tool loaded with interchangeable characters and pressed into an ink pad before being firmly struck against the skin.
Slap tattoos on the shoulder are the standard for commercial hogs headed to slaughter because the mark survives the scalding and dehairing process at the packing plant. This makes it possible to trace a carcass back to its farm of origin even after the ears and tags have been removed during processing. Official swine tattoos, issued and authorized by state or federal animal health officials, are recognized as valid identification for animals in slaughter channels. Registry associations also accept ear or flank tattoos when they’ve been recorded in the association’s book of record.
The equipment for slap tattooing includes a shoulder slapper, interchangeable alphabet and number character sets, an inking box, and tattoo ink. For smaller operations or piglets, a body tattooer designed for baby pigs is a simpler and less expensive option.
RFID Electronic Tags
Radio-frequency identification (RFID) tags represent the newest layer of hog identification. These tags contain a small electronic transponder that stores a unique ID number, readable by a handheld wand or panel reader from a short distance without needing to restrain the animal. RFID has been standard in cattle for years and is now increasingly adopted in the swine industry.
The driving force behind RFID adoption is disease traceability. African Swine Fever, which has spread across multiple continents, poses a serious threat to the U.S. pork industry. If an outbreak were detected, the ability to quickly trace infected animals back to their farm of origin could mean the difference between containing the disease and a widespread crisis. RFID makes that traceback almost instantaneous. When a veterinarian scans the tag, they can pull up ownership records, the premises where the pig originated, and its movement history.
When applying combination visual/RFID ear tags, the visual panel (the male button) goes on the outside back of the ear, and the electronic button (the female portion) sits on the inside of the ear facing inward. This positioning protects the transponder and keeps the visual number readable from behind.
Which Method Fits Your Operation
Purebred breeders typically rely on ear notching because it’s permanent, low-cost, and accepted by registry associations. It also lets you encode litter and individual identity directly on the animal without any equipment beyond a pair of notching pliers. Many breeders combine notching with ear tags for added security, since a tag can fall out but a notch cannot.
Commercial producers sending hogs to slaughter generally use slap tattoos bearing their premises identification number. This is the identification method most likely to survive intact all the way through processing, making it essential for traceback. Ear tags with the premises number are also accepted for feeder and slaughter swine.
Exhibition and show pig programs, including 4-H and FFA, increasingly require RFID tags. Many state fairs and major shows now mandate electronic identification at check-in, and producers need a valid premises identification number to order official RFID tags. Show facilities, commercial sow operations, and state animal health officials can all request these tags through USDA’s APHIS program.
For small farms raising a handful of pigs, simple plastic ear tags are often the most practical starting point. They’re inexpensive, easy to apply, and readable at a glance. If you’re selling animals that will cross state lines or enter any commercial channel, check with your state animal health official about which identification methods satisfy current requirements, as rules vary by state and by the type of movement involved.