The Report of the AVMA Panel on Euthanasia does not provide specific
recommendations for the euthanasia of prenatal or neonatal animals. The
following guidelines are suggested to assist individual Animal Care and Use
Committees at the NIH in reviewing proposals which involve the use of rodent
fetuses or neonates.
Fetuses:
- Fetuses up to 14 days in gestation: Neural development at this stage is
minimal and pain perception is considered unlikely. Euthanasia of the mother or
removal of the fetus should ensure rapid death of the fetus due to loss of blood
supply and non-viability of fetuses at this stage of development.
- Fetuses 15 days in gestation to birth: The literature on the development
of pain pathways suggests the possibility of pain perception at this time.
Whereas fetuses at this age are not sensitive to inhalant anesthetics,
euthanasia may be induced by the skillful injection of chemical anesthetics.
Decapitation with surgical scissors, cervical dislocation, or rapid freezing
(immersion in liquid nitrogen) are acceptable physical methods of euthanasia.
When chemical fixation of the whole fetus is required, fetuses should be
anesthetized prior to immersion in or perfusion with fixative solutions.
Anesthesia may be induced by hypothermia(1) of the fetus, by injection of the
fetus with a chemical anesthetic, or by deep anesthesia of the mother with a
chemical agent that crosses the placenta, e.g., pentobarbital. The institute
veterinarian should be consulted for considerations of fetal sensitivity to
specific anesthetic agents. When fetuses are not required for study, the method
chosen for euthanasia of a pregnant mother must ensure rapid death of the fetus.
Neonates:
- Up to 14 days of age: Acceptable methods for the euthanasia of neonatal
mice and rats include: injection of chemical anesthetics (e.g., pentobarbital),
decapitation, or cervical dislocation. Additionally, these animals are
sensitive to inhalant anesthetics; e.g., methoxyflurane (used with appropriate
safety considerations). Immersion in liquid nitrogen may be used only for
newborns; pups older than one day should be anesthetized prior to freezing with
liquid nitrogen. Similarly, anesthesia should precede immersion or perfusion
with chemical fixatives. Anesthesia may be induced by inhalant or injectable
anesthetics; the institute veterinarian should be consulted for appropriate
agents and dosages. Alternatively, when adequately justified, hypothermia1 may
be used to induce anesthesia in pups six days of age or less.
- Older than 14 days: Follow guidelines for adults.
In all cases, the person performing the euthanasia must be fully trained in
the appropriate procedures.
(1) Phifer CB, Terry LM. 1986. Use of hypothermia for general anesthesia in
preweanling rodent. Physiol & Behav 38:887-890.
Approved by NIH ARAC - February 12, 1997
Revised and Reapproved - November 10, 1998
ARAC Guidelines