A man who allegedly amputated his dog’s leg in a home surgery pleaded not guilty to felony animal cruelty Monday. The dog, named Bart, had been brought into Mother Lode Veterinary Hospital after a dog twice his size had attacked and nearly killed him, according to the nonprofit group Sammie’s Friends website. Sammie’s Friends has a contract to run Nevada County’s animal shelter. At the veterinary hospital, they discovered the dog’s neck muscles were completely torn apart, which turned out to be a blessing in disguise, the website said. If it weren’t for this, Bart would have been able to …