I hadn't heard that one. What's the story?
Here is a link that details the book written by a Secret Service agent. Jimmah was the ‘least likable’ president and I think this man is being kind by putting it like that. The part about the dog is about 2/3 of the way through the article.
http://seanlinnane.blogspot.com/2009/10/secret-service-hated-jimmy-carter.html
He treated the Secret Service horribly. These men would have taken a bullet for bucktooth inbred or his ugly kids and he just treated them all with total contempt. Pppppllllttt.
http://www.history.com/images/media/slideshow/jimmy-carter/jimmy-carter-family.jpg