I'm sorry to hear this - are you certain that his interior yolk sac is out? Unrepairable?
Cervical dislocation is considered a human euthanasia method, even by the AVMA. Rather than breaking the neck, you simply dislocate the connection between the head and the neck.
--------Article from the Canadian Food Inspection Agency-----------
-------link:
http://tinyurl.com/nlg8jz-------------------------------------
Cervical Dislocation
Cervical dislocation is considered a humane method of poultry euthanasia by the American Veterinary Medical Association (AVMA). Use the following steps to perform a cervical dislocation:
1. Place the bird breast-down on a flat surface (or hold the bird against your hip).
2. Use one hand to hold both wings behind the bird's back.
3. Using your other hand, hold the head between your third and fourth fingers, with the third finger on the back of the chicken's head.
4. Sharply turn the head 90 degrees while at the same time pulling it firmly and quickly away from the body (in a motion like stretching the neck). See diagram below. You will feel the vertebra separate.
5. Hold the bird in this position until flapping stops.
Diagram - Cervical Dislocation
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