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The Report of the AVMA Panel on Euthanasia provides limited recommendations
for the euthanasia of prenatal or neonatal animals. The following
guidelines are suggested to assist investigators with protocols
which involve the use of rodent fetuses or neonates.
Fetuses
a) Mouse, Rat and Hamster fetuses up to 14 days’ and Guinea
Pig up to 34 days’ 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.
b) Mouse, Rat and Hamster fetuses 15 days in gestation to birth
and Guinea Pig Fetuses 35 days’ 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
resistant to inhalant anesthetics including CO2 and require extended
exposure, euthanasia may be induced by the skillful injection
of chemical anesthetics. Decapitation with surgical scissors or
cervical dislocation is acceptable physical methods of euthanasia.
Rapid freezing, without prior anesthesia, as a sole means of euthanasia
is not considered to be humane. Animals should be anesthetized
prior to freezing. 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 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 attending 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
a) Mouse, Rat and Hamster Neonates up to 10 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., halothane or isoflurane (used with
appropriate safety considerations). Immersion in liquid nitrogen
may be used only if preceded by anesthesia. Similarly, anesthesia
should precede immersion or perfusion with chemical fixatives.
Anesthesia may be induced by inhalant or injectable anesthetics;
the attending veterinarian should be consulted for appropriate
agents and dosages. Alternatively, when adequately justified,
hypothermia may be used to induce anesthesia in pups six days
of age or less.
b) Mouse, Rat and Hamster Neonates Older than 10 days: Follow
guidelines for adults.
In all cases, the person performing the euthanasia must be fully
trained in the appropriate procedures.
c) Guinea pig Neonates: follow guidelines for adults.
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