Every dog has it's day ... and in the case of the Lab/Chow mix that viciously attacked a little boy only to be scared off by hero cat -- his last day was Saturday.
Sources at the Bakersfield animal shelter tell TMZ ... Scrappy was euthanized at the end of a 10-day hold following the attack. We're told the dog was aggressive during his stay at the shelter, even trying to bite a couple of employees.
Scrappy was so ornery ... we're told he would try to attack staff even when they tried to give him food and water.
RIP Scrappy ... you made a cat a hero.