Question 1

How does the ear punch code system work for identifying rodents?

Accepted Answer

The ear punch code uses standardized notch positions on both ears to create unique animal identifiers. Right ear notches represent single digits (1, 3, 5 for units; double notch for 2), while left ear notches represent tens (10-90). Center holes represent 100 (right ear) and 200 (left ear), with both holes indicating 300. This system allows labeling animals from 1 through 399 by combining notch values.

Question 2

What are the main differences between scissor, thumb, and lever ear punches?

Accepted Answer

Scissor punches avoid pinching motions, reducing carpal tunnel fatigue and injury. Thumb punches are small enough to fit in an Eppendorf tube for easier tissue collection but require a pinching motion. Lever punches are ergonomically superior for thicker ears of older rats. Each design offers distinct advantages depending on your specific research needs and animal age.

Question 3

Why is ear punching best performed on young rats rather than adults?

Accepted Answer

As rats age, their ear skin thickens, making ear punching difficult and causing significant distress without anesthesia. Young rats, ideally when weaned, have thinner, more pliable ears that tolerate the procedure better. For adult rats requiring identification, inhalant anesthesia induction and maintenance laboratory animals should be considered to minimize animal discomfort during ear punching.

Question 4

What are the advantages and disadvantages of metal versus plastic ear tags?

Accepted Answer

Metal tags require picking up the animal to read the code, while plastic tags are easily readable without handling. Plastic tags are compatible with MRI imaging and reduce animal stress from repeated handling. However, both tag types can be lost due to over-grooming, infection, fighting, or self-trauma. Using a secondary identification method like punch codes on the opposite ear prevents identification loss.

Question 5

What positioning errors should be avoided when applying ear tags to rodents?

Accepted Answer

Tags placed too close to the ear edge risk tearing; tags positioned too close to the head can catch neck skin, causing irritation and restricted movement. Tags must not bend the ear, interfere with mobility, or catch on caging. Incorrect positioning leads to self-trauma, infection, and swelling, potentially requiring tag removal and veterinary treatment.

Question 6

How should ear punch tissue samples be prepared for PCR genotyping?

Accepted Answer

Before collecting punch tissue for PCR samples, soak the apparatus in a surface decontaminant solution for at least 3 minutes to remove residual DNA or RNA, then rinse with alcohol. This preparation prevents contamination and ensures accurate genotyping results. Using punches for tissue collection reduces animal stress by eliminating repeat handling for separate sampling procedures.

Question 7

What is the proper procedure for removing an infected ear tag from a rodent?

Accepted Answer

First, moisten a cotton-tipped applicator with antiseptic solution and remove debris around the tag. For severe infections, anesthetize the animal. Using wire cutters, cut across the tag loop edge-to-edge, never the flat surface. Gently guide the tag out with hemostats, avoiding the crimped end to prevent hole enlargement. Wipe the ear with antiseptic and monitor for purulent discharge requiring veterinary follow-up.

Rodent Identification I - Assessment Quiz