This answer is from www.certifiedhumane.org.

The standards were created by a committee of animal scientists and veterinarians with expertise in farm animal issues. The team reviewed the latest research and consulted established standards and guidelines, such as those in use by the Royal Society for the Prevention of Cruelty to Animals (RSPCA) in England, and other standards and guidelines recognized for the humane care of animals. The Animal Care Standards are updated by the scientific committee as new research and information on farm animal welfare becomes available.