Euthanasia of Rodent Fetuses and neonates

IACUC Policy: 046-02, Effective Date: 05/17/2013, Last Revision: 06/17/2016, Last Reviewed: 04/18/2025

Overview/Purpose

The American Veterinary Medical Association (AVMA) guidelines for the euthanasia of animals provides limited recommendations for the euthanasia of fetal and neonatal animals. Data suggests that mammalian fetuses remain in an unconscious state until the time of birth. It is therefore unnecessary to remove and individually euthanize fetuses following euthanasia of a pregnant dam. Euthanasia of the dam alone is sufficient to ensure death of the fetus.

The purpose of this policy is to ensure the appropriate euthanasia of rodent fetuses if removed from the dam and rodent neonates following parturition. 

Definitions

• Fetus: an unborn offspring
• Neonate: a newly born animal
  • Altricial: born in an undeveloped state and requiring care and feeding by the parents. e.g. mice, rats, and hamsters.
  • Precocial: born in an advanced state and able to feed itself almost immediately. e.g. guinea pig pups.
• Gestation: period of development in animals, from the time of fertilization of the oocyte to birth

Requirements

Fetuses

• Mouse, rat and hamster fetuses <15 days post fertilization and guinea pig fetuses < 35 days post fertilization: Euthanasia of the mother or removal of the fetus should ensure rapid death of the fetus due to loss of blood supply.
• Mouse, rat and hamster fetuses at or beyond 15 days post fertilization and guinea pig fetuses at or beyond 35 days post fertilization: Euthanasia method will depend upon the downstream experimental usage and size of the fetus. Acceptable methods to euthanize rodent fetuses include:
  • Overdose of injectable anesthetics
  • Decapitation with surgical scissors
  • Cervical dislocation
  • Rapid freezing in liquid nitrogen (mouse and rat fetuses only)

Death of fetuses (if removed from the uterus) must be confirmed after euthanasia and prior to disposal as for adult rodents.

Neonates

• Resistance to hypoxia at this age results in a prolonged time to unconsciousness when CO2 is used as a euthanasia agent.
• Altricial neonates <10 days of age: (ie: mouse, rat and hamster neonates). Acceptable methods for euthanasia include:
  • Injection of chemical anesthetics (e.g., pentobarbital)
  • Decapitation
  • Cervical dislocation.
  • Overdose of inhalant anesthetics although prolonged exposure may be necessary

Altricial neonates >10 days of age and precocial neonates: Follow euthanasia guidelines for adults.

Additional Information/Guidance

AVMA Guidelines for the Euthanasia of Animals