I took in 2 rescue Yorkies years ago that had come from a puppymill and been de-barked. The female made wheezing noises instead of barking and had a collapsed trachea. It was so sad. The other was a male and when they shoved the metal tube down his throat they broke out his upper and lower teeth. I was told that the millers, some show breeders and larger breeding programs de-bark females so they don't teach their pups to bark to stimuli.
This procedure is inhumane, cruel and should be illegal.
