Guideline #11

Euthanasia of Neonatal Rodents

1. Reference: AVMA Guidelines for the Euthanasia of Animal: 2020 Edition. AVMA. §§S.2.2.4-S2.2.4.2.2, p. 62

2. Purpose/Scope: The purpose of this policy is to provide guidance to principle investigators who may request to euthanize neonatal rodents. This euthanasia guideline primarily applies to laboratory rodents with altricial young (e.g., mice & rats).

3. General: Mammalian fetuses are unconscious in utero due to factors such as low oxygen tension and hormonal influences in the uterus that suppress consciousness. Newborn mouse and rat pups are neurologically immature at birth and their afferent pain pathways are not well developed until after postnatal day 5-7 with cortical development occurring later. The guidelines for euthanizing altricial neonatal rodents (e.g., mouse & rat pups that are born immature, hairless, eyes closed, etc.) are different than the guidelines for euthanizing precocial neonatal rodents (e.g., guinea pigs) which should be treated as adults.

4. Rodent Fetuses: Prior to parturition fetuses in utero are typically euthanized by euthanizing the dam/mother using an AVMA acceptable method of euthanasia. It is not necessary of required to remove the fetuses from the uterus after the dam/mother is euthanized. Some of the euthanasia methods listed below in paragraph 5 below may also be used for euthanizing fetuses.

5. Neonatal Altricial Rodents (e.g., Mice & Rats): Neonatal rodents that are ≤7 days old may be euthanized by any of the following methods unless otherwise noted. Euthanasia guidelines for adults should be followed for neonatal rodents that are >7 days old.

5.1. Recommended Euthanasia Methods:

5.1.1. Injectable anesthetic overdose administered by IP injection (e.g., pentobarbital) [fetuses & neonates].

5.1.2. Inhalation anesthetic overdose (e.g., isoflurane, CO2, etc.) followed by decapitation or cervical dislocation once the neonate is unconscious and unresponsive to painful stimuli in order to insure death.

5.1.3. Decapitation with scissors or a sharp blade [fetuses & neonates].

5.2. Conditionally Acceptable Euthanasia Methods with Adequate Scientific Justification:

5.2.1. Cervical dislocation [fetuses & neonates]

5.2.2. Hypothermia (i.e., gradual cooling) – Hypothermia is acceptable provided the neonates are <10 days old, don’t come into direct contact with ice or cold surfaces, and are decapitated or cervically dislocated once the neonate is unconscious and unresponsive to painful stimuli in order to insure death. [fetuses & neonates].

5.2.3. Rapid freezing – Mouse and rat fetuses and neonates <5 days old may be quickly killed by rapid freezing in liquid nitrogen (N2) [fetuses & neonates].

6. Neonatal Precocial Rodents (e.g., Guinea Pigs): Precocious neonatal rodents should be euthanized using the same guidelines for euthanizing adults.

7. Euthanasia shall be performed by trained personnel.

8. Euthanasia methods that deviate from this guideline and/or the referenced AVMA euthanasia guidelines must be scientifically justified and approved by the IACUC on a case by case basis.

LAST REVIEWED AND ADOPTED BY THE IACUC: July 02, 2026