Step 7: Additional info
AVMA & humane euthanasia
or from the University of Iowa:
University of Iowa Animal Research
Guidelines for the Euthanasia of Rodent Feti and Neonates
Yale University's IACUC co2 euthanasia guidelines
University of California's euthanasia guidelines
Please note that these guidelines apply mostly to laboratory animals, as some mention the use of barbituates and other gases. But, the CO2 method is widely practiced and acceptable as a rather humane way to euthanize small animals.