Identification and Numbering

The System

Every laboratory beagle must be individually identifiable. This is a regulatory requirement under the Animal Welfare Act, which mandates that dealers and research facilities maintain records for each dog, including a description and identification number. The identification system serves record-keeping, not the animal.

3 primary methods are used, often in combination:

• Ear tattoos — ink numbers or alphanumeric codes applied inside the ear (pinna). This is the oldest and most widespread method.
• Microchips — small transponders (about the size of a grain of rice) injected subcutaneously, typically between the shoulder blades. Each chip carries a unique numeric code readable by a scanner.
• Cage cards — paper or plastic cards attached to the front of each enclosure, displaying the animal's identification number, study assignment, dosing information, and other protocol details.

Ear Tattoos

The ear tattoo is the most visible form of identification. It is applied during the weaning period, typically at 6-8 weeks of age, at the breeding facility.

The process involves restraining the puppy and using a tattoo clamp or electric tattoo pen to imprint ink into the inner surface of the ear. The clamp method presses inked needles through the ear skin in a single action. The pen method involves repeated needle punctures tracing each character.

• No anesthesia is standard — most facilities perform ear tattooing without local or general anesthesia. The procedure is considered minor, though puppies vocalize and struggle during application.
• "Branding" — advocates and some veterinary professionals have described the procedure as branding. The comparison is not rhetorical — it is the permanent marking of a living being with a production number for the purpose of tracking it as inventory.
• Fading and illegibility — ear tattoos can fade over time, become obscured by ear pigmentation, or be damaged by ear infections or handling. This is one reason microchips are increasingly used as a backup or replacement.

The Codes

Laboratory beagles are assigned alphanumeric codes — combinations of letters and numbers that encode facility of origin, birth cohort, and individual sequence. A typical identifier might read something like "MBR-2024-0847" or "F-6291."

These codes are the dog's identity within the research system. Study reports, veterinary records, regulatory submissions, and euthanasia logs all reference the code, never a name. Technicians who work with the dogs daily may informally name them, but official documentation uses only the assigned number.

The code follows the dog from birth to death. It appears on:

• Breeding records at the facility of origin
• Health certificates and transport documents
• Cage cards at the receiving laboratory
• Study protocols and data sheets
• Necropsy reports
• USDA annual reports (aggregated, not individual)

Multiple Tattoos

Dogs that move between facilities may accumulate multiple tattoos. Each institution has its own numbering system, and a dog transferred from a breeder to a CRO to a university laboratory might receive a new tattoo or additional marking at each stop.

• Breeder tattoo — applied at Marshall or another breeding facility during the weaning period.
• CRO tattoo — applied upon arrival at a contract research organization, linking the dog to the receiving facility's records.
• Study-specific marking — some protocols require additional identification (dye marks, collar tags) to distinguish treatment groups.

A dog with 2 or 3 tattoos inside its ears carries a physical record of its institutional history — each mark representing a different organization that claimed ownership and used the animal for its purposes.

Microchips

Microchip implantation is increasingly common as either a supplement to or replacement for ear tattoos. The chip is injected using a large-bore needle, typically without anesthesia, into the subcutaneous tissue between the shoulder blades.

• Advantages — permanent, cannot fade or become illegible, scannable without handling the ear, compatible with automated data systems.
• Limitations — requires a scanner to read (not visually identifiable), chips can migrate from the implantation site, and chip failure (though rare) renders the dog unidentifiable by that method.

Most large facilities now use both tattoos and microchips, creating redundant identification.

Cage Cards

The cage card is the public-facing identifier. It hangs on the front of the dog's enclosure and displays:

• Animal identification number
• Species, breed, sex, age
• Study number and sponsor
• Dosing group and dose level
• Veterinary notes and clinical observations
• Start date and projected study termination date

The cage card tells anyone walking through the facility exactly what this dog is for, what is being done to it, and when it will be killed. It is updated as the study progresses. When the dog is euthanized, the cage card is archived with the study records.

What a Name Means

The absence of names is not accidental. Naming creates attachment. Attachment complicates the willingness to perform invasive procedures, administer toxic doses, and euthanize the animal at study termination.

The identification system is designed to maintain psychological distance between the humans who use the dogs and the dogs themselves. A number is a unit of production. A name is an individual. The research system requires units, not individuals.

Some technicians name the dogs anyway. This informal practice is tolerated but not officially recorded. When those technicians describe their work to researchers studying the psychology of laboratory workers, the emotional cost of this disconnect — between the named individual they care for and the numbered subject they dose and restrain — is a recurring theme.

Sources

1. 1.USDA AWA Identification Requirements, 9 CFR 2.50. Federal regulations requiring individual identification of dogs by research facilities and dealers, including acceptable methods.
2. 2.Laboratory Animal Management Standards, 2021. Published standards for animal identification, record-keeping, and traceability in GLP-compliant research facilities.