Swine Ear Notching Laws in Idaho: What Producers Need to Know

Ear notching is one of the oldest and most practical ways to identify pigs, but whether it meets Idaho’s legal requirements for official identification depends on exactly how and why you’re using it. For small-scale producers, 4-H participants, and commercial hog farmers alike, understanding the difference between a farm-management notch and a legally recognized identification method can prevent costly compliance problems at sale barns, state lines, and breed registry offices.

Idaho follows the federal Animal Disease Traceability (ADT) framework administered by USDA APHIS, and the Idaho State Department of Agriculture (ISDA) enforces its own import and movement rules on top of that baseline. Ear notching sits in a specific — and sometimes misunderstood — place within that system. This guide walks you through every layer of Idaho’s swine identification rules that touch ear notching, from the mechanics of the 1-3-9 system to the moments when a notch alone simply is not enough.

What Is Swine Ear Notching and When It Is Used in Idaho

Ear notching is a permanent identification method that uses a V-shaped notcher tool to cut small, precise notches into specific locations on a piglet’s ears. Each position on each ear carries a numeric value, and the combination of notches encodes a unique litter number and individual pig number that can be read at a glance throughout the animal’s life. An accurate set of records on swine performance is one of the best management tools a producer can have, and keeping such records requires the ability to identify pigs from birth.

The simplest identification method, and the one recommended by most breed associations, is ear notching. The most common notching system is the 1-3-9 system. In Idaho, producers use ear notching in several distinct contexts: purebred herd management, 4-H and youth livestock projects, fair and show entry, and compliance with breed registry requirements. The practice is also common on smaller operations where RFID infrastructure is not yet in place.

Time for notching is an important factor. If pigs can be notched when their tails are docked, or at 1–3 days old, the task is much easier. Performing the procedure at this stage minimizes stress on the animal, reduces bleeding, and ensures the notches heal cleanly before the piglet grows large enough to make restraint difficult.

Pro Tip: Disinfect your V-notcher between every litter — not just between sessions. Cross-contamination during processing is a preventable biosecurity risk that Idaho’s own animal disease rules take seriously.

When Ear Notching Qualifies as Official Identification in Idaho

The USDA Animal Disease Traceability (ADT) program defines official animal identification and recording requirements for the interstate movement of animals. Idaho administers this program through ISDA, and the rules draw a clear line between ear notches that count as official ID and those that do not.

Ear notching qualifies as official identification if the ear notching has been recorded in the book of record of a purebred registry association. This is a narrow carve-out. A notch applied on your farm for your own record-keeping purposes — even a perfectly executed 1-3-9 notch — does not automatically become official identification just because it exists. The registry recording requirement is what elevates it to official status.

Other identification types, such as brands, unregistered notches/tattoos, or farm/ranch tags are not considered official identification for the purpose of interstate movement. If you plan to move swine across state lines into or out of Idaho, relying on an unregistered notch will put you out of compliance with both ISDA and federal ADT requirements. For those situations, you need an approved ear tag or other official method.

Swine may enter the state of Idaho provided they are individually identified by official ear tags or other approved techniques indicating the state and herd of origin and they are accompanied by a certificate of veterinary inspection. That certificate requirement applies regardless of which identification method you use.

Important Note: If you raise swine that will ever leave Idaho for sale, shows, or breeding, do not rely solely on ear notching unless those notches are formally recorded with a recognized purebred registry. Plan your identification strategy before the animals are born, not the day before they ship.

How the 1-3-9 Ear Notching System Works

The 1-3-9 system assigns numeric values to specific zones on each ear. Reading the system correctly requires you to always view the pig’s ears from the pig’s own perspective — not from the front as you face the animal. The reference to left and right ear refers to the pig’s left or right ear as viewed from the rear of the pig. Left and right does not refer to the viewer’s left or right in a situation where the pig is facing the viewer.

The right ear is used for the litter mark, and all pigs in the same litter must have the same notches in this ear. The litter mark ear is divided into five sections, and each section has a numerical value — either 1, 3, 9, 27, or 81. Each section, except for 81, can have one or two notches only.

The left ear is used for notches to show an individual pig’s number in the litter. Each pig will have different notches in the left ear. The left ear is divided into three sections, with values of 1, 3, and 9. You arrive at any number by adding the values of the notches present. For example, a pig in litter 10 with individual number 4 would have right-ear notches totaling 10 (9+1) and left-ear notches totaling 4 (3+1).

Ear	Purpose	Zone Values Available	Max Notches per Zone
Right (pig’s right)	Litter number	1, 3, 9, 27, 81	2 (except 81: 1 only)
Left (pig’s left)	Individual pig number	1, 3, 9	2 per zone

In zones 1, 3, 9, and 27, there can only be two notches — two notches in all four zones would represent Litter 80. A notch in zone 81 basically doubles the system. This means a single producer can track litter numbers well past 160 without running out of combinations.

Small notchers typically make a notch that is 3/16 to 1/4 inch deep, which is the preferable size for pigs under 25 pounds. For larger pigs, a notcher that makes notches 1/2 inch deep is recommended. Avoid making notches too shallow, as they may become hard to read or possibly heal shut. Leave at least 1/4 inch between notches, and avoid making notches too close to the head.

Pro Tip: A quick memory trick used widely in 4-H programs: think of the ear notch as the pig’s first and last name. The right ear is the “last name” (litter), and the left ear is the “first name” (individual pig). Always write it litter number first, then a dash, then the individual number — for example, 14-3.

Ear Notching for Purebred Registry Compliance in Idaho

For Idaho producers raising registered purebred swine — Berkshire, Duroc, Hampshire, Yorkshire, Chester White, Landrace, Poland China, or Spotted — ear notching is not optional. It is the primary identification method required by most breed associations to enroll animals in their books of record, and that enrollment is what makes the notch legally meaningful under federal ADT rules.

Ear notching qualifies as official identification when the ear notching has been recorded in the book of record of a purebred registry association. Tattoos on the ear or inner flank of any swine similarly qualify if the tattoos have been recorded in the book of record of a swine registry association. Both methods share the same requirement: the marking must be on file with a recognized registry before it carries any official weight.

Organizations such as the National Swine Registry and Certified Pedigreed Swine provide breed-specific ear notching charts and enrollment documentation. When you register a litter, you submit the notch pattern along with dam and sire information, and the registry assigns a permanent record number. That number — tied to the notch — is what satisfies the “book of record” requirement under federal and Idaho state rules.

Idaho 4-H swine projects also depend on registered notch records. County extension offices require participants to submit ear notch identification forms before show enrollment, and judges at state fairs verify notch patterns against submitted records. If the notch on the pig does not match the paperwork, the animal can be disqualified. Submit your notch forms early and double-check them against the pig before show day.

Ear Notching vs. Ear Tags, Tattoos, and RFID in Idaho

Idaho producers have several identification tools available, and each one has a different legal standing depending on the situation. Understanding where ear notching fits — and where it falls short — helps you build a compliant identification strategy from the start.

Method	Official for Interstate Movement?	Official for Purebred Registry?	Requires PIN?	Permanent?
Ear Notching (registered)	Yes — if recorded with registry	Yes	No	Yes
Ear Notching (unregistered)	No	No	No	Yes
Official Ear Tag (metal/visual)	Yes (swine)	No	Yes (PIN-based)	Yes
RFID 840 Tag	Yes	No	Yes	Yes
Tattoo (registered)	Yes — if recorded with registry	Yes	No	Yes
Farm/Ranch Tag	No	No	No	No

Producers and veterinarians ordering official identification tags require a Premises Identification Number (PIN). Producers and veterinarians can order RFID tags from any manufacturer — just make sure they have the USDA shield and start with the numbers 840 to ensure they are official identification. The 840 prefix is a non-negotiable requirement; tags starting with any other number are not considered official under Idaho or federal rules.

Producers can also order free RFID tags from ISDA by completing an order form or contacting ISDA. ISDA has several RFID readers available to loan, free of charge, to Idaho livestock producers. The reader rental program is intended to provide producers an opportunity to utilize RFID technology without requiring the purchase of an RFID reader. This is a practical resource for smaller Idaho operations that want to adopt RFID without a large upfront equipment investment.

For slaughter and feeder swine specifically, an ear tag or tattoo bearing the Premises Identification Number assigned by the State Animal Health Official to the premises on which the swine originated is the required identification method. Ear notching alone — even registered notching — does not satisfy this requirement for commercial slaughter channels.

If you raise both registered purebred breeding stock and commercial market hogs, the practical approach is to use registered ear notching for your purebred animals and PIN-based ear tags or RFID for any pigs moving through commercial channels. Many Idaho producers run both systems simultaneously on the same operation. You can learn more about how Idaho structures livestock transport documentation requirements before you schedule your next shipment.

State-Specific Swine Identification Rules That Affect Ear Notching in Idaho

ISDA administers identification requirements for swine under the USDA Animal Disease Traceability (ADT) program, which defines official animal identification and recording requirements for the interstate movement of animals. Idaho’s rules layer on top of the federal baseline and address both inbound and outbound swine movement.

For swine entering Idaho, animals may enter the state provided they are individually identified by official ear tags or other approved techniques indicating the state and herd of origin and are accompanied by a certificate of veterinary inspection. Every animal entering Idaho requires a Certificate of Veterinary Inspection (CVI). Some require an entry permit. Contact ISDA’s Animal Industries division or visit the ISDA Avian and Swine Identification page to confirm current entry permit requirements for your specific situation before animals move.

Goats, swine, and other livestock species are subject to their own separate movement and identification requirements under Idaho law, which are distinct from the brand inspection system that covers cattle and equines. This is a point many new swine producers miss: the brand inspection rules you may have heard about for cattle do not apply to your hogs. Swine identification in Idaho operates entirely under the ADT framework, not the brand board system.

• Intrastate movement (within Idaho): Ear notching, farm tags, and other on-farm methods are generally sufficient for moving pigs between your own premises or to a local sale barn, but confirm with ISDA if the destination requires a CVI.
• Interstate movement (leaving or entering Idaho): Official identification — registered notch, PIN-based ear tag, or RFID 840 tag — plus a CVI is required. Unregistered notches do not qualify.
• Slaughter and feeder swine: A PIN-based ear tag or tattoo is required; registered ear notching alone does not satisfy this channel’s rules.
• Shows, fairs, and exhibitions: Idaho county fairs and the state fair require official identification on project animals. Registered ear notches recorded with a recognized breed association satisfy this requirement for purebred show pigs.
• Disease-positive or exposed animals: All seropositive and infected swine are to be individually identified by placing an ear tag in the left ear of the animal. The reactor tag number shall be recorded on movement documents. Ear notching has no role in this disease-response protocol.

Important Note: Idaho swine identification rules can be updated through the ISDA rulemaking process. Always verify current requirements directly with ISDA’s Animal Industries division before moving animals, especially for interstate shipments. The ISDA contact number for swine identification questions is listed on their official ADT page.

If you raise other livestock species alongside your swine operation, Idaho’s identification and movement rules vary significantly by species. Review the state’s goat ownership laws for how caprine identification differs from swine rules, and check the pet and animal import laws if you are bringing any animals into Idaho from another state. Producers who also keep poultry will find the backyard chicken laws in Idaho and rooster laws useful for understanding how ISDA handles avian identification separately from swine. For those managing mixed rural properties, the beekeeping laws in Idaho and kennel zoning laws round out the regulatory picture across species.

Ear notching remains a practical, low-cost, and permanent identification tool for Idaho swine producers — but its legal standing depends entirely on context. Register your notches with a recognized breed association if you raise purebred stock, pair them with PIN-based tags for any commercial movement, and always have a CVI ready when animals cross state lines. Getting the identification right from day one protects your animals, your records, and your ability to move pigs when and where your operation demands it.