Swine Ear Notching Laws in Missouri: What Producers Need to Know
July 28, 2026
Missouri ranks among the top swine-producing states in the country, and the rules governing how you identify your hogs matter far more than most producers realize until a movement or show is denied. Ear notching is one of the oldest identification methods in the swine industry — but under Missouri and federal law, it only qualifies as official identification under specific, narrow conditions.
Whether you raise purebred Berkshires, show pigs at the county fair, or run a commercial farrow-to-finish operation, understanding exactly when an ear notch counts, when it does not, and what else the state requires will save you from compliance headaches at the sale barn, the state line, or the exhibition ring. This guide walks through every layer of Missouri’s swine ear notching rules so you can act with confidence.
What Is Swine Ear Notching and When It Is Used in Missouri
Ear notching is a permanent identification method that involves cutting small V-shaped notches into specific positions on a pig’s ears at or shortly after birth. Ear notching is widely used in the swine industry as a system of animal identification, with all variations identifying a pig by litter number and individual pig number. Because the marks are made directly on the animal’s tissue, they cannot be lost, removed, or swapped the way a plastic tag can be.
In Missouri, ear notching appears in two very different contexts. The first is as a farm management tool — a practical, low-cost way for any producer to track litters and individual animals within a closed herd without relying on tags or electronic devices. The second is as a potential form of official identification recognized by state and federal regulators. Those two contexts carry very different legal weight, and confusing one for the other is a common and costly mistake.
Missouri’s swine industry spans everything from large commercial confinement operations in the northwest part of the state to small heritage-breed farms and 4-H show projects. Ear notching remains common across all of those settings, but its regulatory role differs depending on the animal’s status, destination, and registration history. If you keep swine in Missouri — even as a hobby or for a single fair entry — you need to know which context applies to your animals.
Pro Tip: Even if you use ear notching purely for on-farm management, apply notches at farrowing and record them in your farm log immediately. Good records protect you if an animal’s identity is ever questioned during a veterinary inspection or market transaction.
When Ear Notching Qualifies as Official Identification in Missouri
Not every ear-notched pig in Missouri carries official identification — far from it. According to the Missouri Department of Agriculture’s Animal Disease Traceability program, ear notch qualifies as an official identification method only if the animal is registered with a purebred association. That single condition is the dividing line between a management mark and a legally recognized ID.
Per the USDA APHIS National Veterinary Accreditation Program (NVAP) Reference Guide (as of January 2026), ear notching qualifies as official swine identification only if the ear notching has been recorded in the book of record of a purebred registry association. Missouri’s state rules mirror this federal standard exactly. If the notch is not on file with a recognized registry, it has no official standing for interstate movement, market entry, or exhibition purposes.
Existing regulations require that swine must be officially identified at whichever of the following comes first: the point of first commingling in interstate commerce with swine from any other source, upon unloading in interstate commerce at any livestock market, or upon transfer of ownership in interstate commerce — and all swine entering Missouri require individual, official identification listed on their Certificate of Veterinary Inspection (CVI). An unregistered pig with a notch in its ear does not meet that requirement.
For exhibition animals, the University of Missouri Extension has clarified the state’s rules: acceptable swine identification for exhibition includes a registration tattoo and registration papers from the appropriate breed association, or for unregistered swine, an ear notch accompanied with farm records. That second option — ear notch plus farm records — applies specifically within Missouri’s exhibition framework and does not substitute for official ID in interstate or commercial movement contexts.
How the 1-3-9 Ear Notching System Works
The system used by purebred swine associations across the United States — and the one Missouri producers and 4-H participants are expected to follow — is the universal ear notching system built on the values 1, 3, 9, and 27. Understanding how to read and apply it correctly is not optional if you plan to register animals or use notching as an official identification method.
The universal ear notching system is based on the fact that a pig has two ears. The pig’s right ear, as viewed from the rear of the pig, is designated as the “litter” ear, and notches in this ear tell the producer which litter the pig was born to. The pig’s left ear designates the pig number within the litter, so the first piglet is pig number one, the second is pig number two, and so on.
Each ear is divided into four quadrants, with each quadrant representing a number. The outside bottom quadrant represents the number 1 — if there are two notches in that quadrant, the number is 1+1 or 2, and there will never be more than two notches in any quadrant. The outside top quadrant represents the number 3, and the inside top quadrant represents the number 9.
In the litter ear only, the inside bottom represents the number 27, and the notch in the very tip of the right ear signifies litter number 81. This tip notch effectively doubles the system, allowing producers with large sow herds to represent litter numbers well beyond 80. There are five designated zones — 1, 3, 9, 27, and 81 — in the litter ear and three designated zones — 1, 3, and 9 — in the individual pig ear. In zones 1, 3, 9, and 27, there can only be two notches, so two notches in all four zones represents litter 80, and a notch in zone 81 doubles the system.
To read a notch combination, you add up the values of all notched positions in each ear. The litter number is always mentioned or written first, followed by a dash. For example, a pig with the ear notch of 33-7 would have two notches in the “3” location on the right ear and one notch in the “1” location on the right ear (3+3+1=7 for the individual number), while in the litter ear, one notch in the “27” region and two notches in the “3” region (27+3+3=33) give the litter number.
Pro Tip: A reliable way to avoid reading errors in the field is to always look the pig in the face first. Since confusion over which ear is the “left ear” can easily occur depending on whether you view the pig from the front or rear, looking the pig in the face and reading left to right will always give you litter number then pig number.
Notching is performed with a dedicated ear notcher tool, ideally within the first few days after birth when the tissue is thin and healing is fast. Ear notches help breeders maintain accurate records for registration and for health records on the farm, including vaccination records. Accuracy matters: a misplaced notch on a registered animal can create a mismatch between the physical pig and its registry record, which can disqualify it from showing or sale as a purebred.
Ear Notching for Purebred Registry Compliance in Missouri
If you raise registered swine in Missouri — Berkshire, Duroc, Hampshire, Yorkshire, Chester White, Landrace, Poland China, or Spotted — the ear notch is not just a farm tool. It is the foundation of your registry record and, under both state and federal rules, your animal’s official identification. Getting it right at farrowing protects every downstream transaction the animal will ever be part of.
Each ear is divided into four parts, with each area representing the numbers 1, 3, 9, or 27, and in each of the four areas you can have up to two notches. The right ear is used for the litter mark, and all pigs in the same litter must have the same notches in the right ear. The left ear identifies individual pigs in the same litter, and all littermates must have different notches in the left ear. No more than two notches may be made at any position.
Once the notch is applied and recorded with your breed association, that record becomes the animal’s book-of-record entry. Ear notching qualifies as official swine identification if the ear notching has been recorded in the book of record of a purebred registry association. This means the registration paperwork — not the notch alone — is what creates official status. Keep your registration certificates with the animal whenever it moves off your farm.
Major national registries that Missouri producers work with include the National Swine Registry (covering Duroc, Hampshire, Yorkshire, and Landrace) and Certified Pedigreed Swine (covering Berkshire, Chester White, Poland China, and Spotted). Both organizations use the same universal 1-3-9 notching system described above, though they may have breed-specific record-keeping requirements. Contact your registry directly before farrowing season to confirm their current submission procedures.
Breed registry tattoos must be recorded with a purebred registry association, and the registration certificate must accompany the animal. The same logic applies to ear notches: the physical mark and the paper record are inseparable for compliance purposes. If you lose the registration certificate, contact your registry for a duplicate before the animal needs to move.
Ear Notching vs. Ear Tags, Tattoos, and RFID in Missouri
Missouri recognizes multiple official swine identification methods, and each has a different scope of applicability. Knowing which method fits which situation prevents delays at the sale barn, the state line, or the show ring. The table below summarizes how the main options compare under Missouri and federal rules.
| Identification Method | Official Status in Missouri | Applicable Animal Types | Key Limitation |
|---|---|---|---|
| Ear Notch | Official — if recorded with purebred registry | Registered purebred swine | No official standing for commercial or unregistered swine |
| 840 RFID Tag | Official for all swine | All swine categories | Requires premises ID number (PIN) |
| USDA Silver Tag (8–9 characters) | Official for all swine | All swine categories | Obtained through Missouri Department of Agriculture |
| PIN Tag | Official for slaughter swine | Slaughter swine only | Not valid for breeding or exhibition animals |
| Ear or Inner Flank Tattoo | Official — if recorded with purebred registry | Registered purebred swine | Same registry-recording requirement as ear notch |
| Microchip | Official | Pet pigs | Applies specifically to pet pig category |
| USDA Backtag | Temporary — slaughter only | Swine going directly to slaughter within 3 days | Not a substitute for permanent ID in any other context |
Animals which would otherwise require identification may go directly to an approved slaughter facility, to be slaughtered within 3 days, with a USDA-approved backtag in lieu of other identification. That narrow backtag exemption is the only situation in which a non-permanent method substitutes for official ID, and it applies exclusively to the slaughter pipeline.
For most Missouri producers moving breeding stock, the 840 RFID tag is the most flexible option because it applies to all swine regardless of registration status. AIN tags begin with the official country code “840” for the United States, followed by 12 digits, and are available with radio frequency identification technology that allows them to be readable both visually and electronically. If your herd is a mix of registered and unregistered animals, RFID tags eliminate the need to track which animals have registry-backed ear notches and which do not.
Ear notching and ear tags are not mutually exclusive. Many Missouri purebred producers apply both — the notch at birth for registry purposes and an RFID tag before the animal leaves the farm — to ensure compliance across every possible movement scenario. This belt-and-suspenders approach is especially practical for show pigs that may travel to multiple events in a season. You can learn more about how Missouri handles pet pig import requirements separately, as microchip rules for pet pigs operate under a different framework than commercial swine ID.
State-Specific Swine Identification Rules That Affect Ear Notching in Missouri
Missouri’s swine identification framework pulls from both state regulations and federal Animal Disease Traceability (ADT) rules, and the two layers interact in ways that directly affect when an ear notch is sufficient and when you need something more. Understanding the full picture keeps your operation compliant no matter where your animals go.
All animals entering Missouri must be accompanied by an official Certificate of Veterinary Inspection (CVI, health certificate) issued within 30 days prior to movement into Missouri, unless moving to an approved slaughter facility or to an approved livestock market. The identification method listed on that CVI must be one that Missouri accepts as official — which means an ear notch is only acceptable on that CVI if the animal is registered with a purebred association.
Swine moving in a group or lot production system and entering Missouri must be individually identified by an official ear tag, group/lot identification number, ear notch, tattoo, or any other means of permanent identification approved by the state veterinarian and listed on the CVI, and must originate from a validated swine brucellosis-free state or validated brucellosis-free herd, and from a pseudorabies Stage V state or from a qualified negative pseudorabies herd. Disease status documentation travels with the animal, not just the ID.
All sows and boars sold for slaughter are to be individually identified — by official eartag, tattooed, backtagged, or identified by any other means of permanent identification approved by the state veterinarian — at the first point of concentration. This rule applies at licensed Missouri livestock markets and means that even slaughter animals need a recognized form of ID before they change hands at auction.
Market-to-market movement of swine into and within Missouri is prohibited except to slaughter-swine-only markets, and all commercial swine bought at a market or sale consigned to a farm or premises will be quarantined to the point of destination for a minimum of 30 days. That quarantine requirement is a key reason accurate individual identification matters: if an animal’s ID is disputed, the quarantine period and any associated disease testing become your problem to resolve.
A new Animal Disease Traceability rule was proposed and amended on May 9, 2024. Missouri producers should verify with the Missouri Department of Agriculture Animal Disease Traceability page that their identification practices align with the most current federal requirements, as ADT rules can affect which methods are accepted for interstate movement. You can reach the Missouri Department of Agriculture Animal Health Division directly at (573) 751-3377, Monday through Friday, 7:30 a.m. to 5 p.m. CST.
Important Note: Missouri’s exhibition rules for swine were updated by the Missouri Department of Agriculture, with new rules going into effect for county fairs and exhibitions. New exhibition rules issued by the Missouri Department of Agriculture for showing cattle and swine at county fairs and exhibitions went into effect, and University of Missouri Extension specialists noted the changes encourage healthy animals. Confirm current exhibition ID requirements with your county extension office before fair season.
For producers moving animals across state lines, the USDA APHIS NVAP Swine Identification Reference Guide is the authoritative federal source for approved ID methods, and Missouri’s rules align with it. The Missouri Code of State Regulations, 2 CSR 30-2, contains the full text of the state’s animal health movement requirements. Reviewing both documents before any interstate transaction is the best way to avoid a compliance gap.
Missouri’s brucellosis rules in Missouri and backyard animal regulations follow a similar pattern of layered state and federal requirements. If you also keep other livestock or poultry alongside your swine operation, reviewing those rules alongside your swine ID obligations gives you a complete picture of your compliance responsibilities. For broader context on how Missouri governs animal ownership and movement, the pet laws in Missouri overview covers the state’s general animal regulatory framework.
Ear notching in Missouri is a precise practice with precise legal boundaries. Apply the notch correctly at farrowing, record it with your breed association, keep the registration papers with the animal, and pair it with an RFID tag when the animal will move commercially or across state lines. Do those four things, and you will meet every identification requirement Missouri and federal law place on your registered swine.