sentences:  When all options have been investigated and none of these measures are feasible without causing stress or impacting upon group behaviour and the decision is taken that it is necessary to euthanize an animal, care will be taken to ensure it is carried out in a fear free environment and a manner that ensures a quick death without suffering.Euthanasia may be controlled by local customs and laws but should always be used in preference to keeping an animal alive under conditions which do not allow it to experience an appropriate quality of life.Whenever possible a post-mortem examination should be performed and biological material preserved for research and gene conservation.