5. Rabbit Management 
Vol, 6, No. 12 
Page 3 
W. R. Edwards, D. A. Casteel 
During the study of reproductive behavior and the timing of ovulation, it was 
necessary to develop a satisfactory method of immobilizing cottontails so that 
their reproductive status could be determined without killing them. Intravenous 
injection of 30-50 mg/kg (about 0,5 cc for the average size cottontail) of penta- 
barbital sodium (Nembutal, Abbott) into the medial auricular vein of the ear proved 
to be a very satisfactory method of inducing surgical anesthesia in cottontails 
(Table 1). Loss due to shock and over-dosage was low, the recovery period was 
relatively short, and immobilization was rapid. Injection of pentabarbital sodium 
into the vein of the ear usually induced surgical anesthesia for periods of 20-40 
minutes. When it is desirable to sustain anesthesia during surgery, pentabarbital 
sodium can be sprayed on the intestines in 0.2 cc doses as needed. 
The drug was administered in 0.1 cc doses at approximately 5" to 10-second 
intervals. Because of the relatively small diameter of the medial auricular vein, 
a 27-gauge, ^-inch needle on a 0e5"CC syringe is recommended for administration of 
the Nembutal. Injecting Nembutal laterally into the auricular vein proved easier 
than administering it through a vertical presentation down the main trunk of the 
vein. The 0.5~cc syringe is suggested because less physical pressure is required 
to inject the drug through a 27-guage needle used on a small syringe than when a 
needle of this size is used on a larger syringe. Also, the drug can be adminis¬ 
tered more accurately with a small syringe. 
Cottontails do not struggle or otherwise react violently to Nembutal during 
induction; however, deepened respiration, accelerated heart beat, salivation, and 
elimination of urine occasionally occur. With experience, the researcher can feel 
the rabbit's response to Nembutal while he holds the animal and administers the 
drug, and can adjust the dosage accordingly. Satisfactory anesthesia is normally 
attained almost immediately and cnn be determined by the failure of the animal to 
exhibit a muscular reflex (pedal reaction) when membranes between the toes of the 
hind feet are pinched. Laparotomies of cottontails, anesthetized by the described 
procedure, were successfully and routinely performed. Several does survived two 
such operations at intervals of 6-10 days. During t h ‘s study, intra-uterine mor¬ 
tality followed administration of drugs to pregnant does. It is not now known 
whether the intra-uterine mortality was caused by the drug's effect on the neural 
O 2 center or by the stresses of capture, handling, and surgery. 
