The following two links are worth reading:

"....in New York, Henry Bergh, founder of the ASPCA, urged the city to make humane reforms at the pound while steadfastly refusing to let the ASPCA run it. He believed that operating the city’s pound could conflict with the society’s role as an advocate for animals and place undue financial strain on the organization. Bergh’s foresight was remarkably accurate; more than a century later many humane organizations are divesting themselves from animal control responsibilities for some of the same reasons cited by Bergh in the 1800s.iii"

http://www.aspca.org/site/DocServer/From_Impound_to_Humane_Community.pdf?docID=6841

http://www.aspca.org/site/DocServer/Understanding_Humane_Organizations.pdf?docID=6842