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Guidelines
For The Euthanasia Of Mouse And Rat Fetuses And Neonates
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 |
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