Greyhound trainers, who race dogs a few miles from where a man was said to be slaughtering thousands of animals, said they were unaware of his activities.
David Smith has installed security at his home
More than 20 trainers who race at Sunderland Greyhound Stadium said they were as "horrified as the public".
A Sunday Times investigation claimed David Smith, of Seaham, County Durham, had shot 10,000 dogs with a bolt gun and buried them in his allotment.
Durham Police said Mr Smith has committed no offence.
They said the builders' merchant held the bolt gun legally.
But greyhound trainers at the Sunderland stadium stressed none knew of Mr Smith's alleged activities.
Spokesman Andrew Bell said: "We are aware that members of the public have made the assumption that this is the norm with retired greyhounds. This is not normal.
"As professional greyhound trainers, we abide by all the National Greyhound Racing Club rules, particularly those relating to the euthanasia of greyhounds, and when necessary this is always done by a registered veterinary surgeon."
Mr Bell, who races greyhounds at Brough Park in Newcastle, said no-one knew of Mr Smith's reported activities.
David Hood, director of racing at the Sunderland Greyhound Stadium, said: "Nobody has heard of this fellow and nobody was aware of this activity going on."
Mr Bell added: "We have no time for anyone who mistreats a dog, be it a greyhound or domestic pet, and as professionals we resent the way it has been reported.
"It has cast a shadow over the sport and our profession and we would welcome any investigation ... to identify the individuals who may have been involved with these allegations."
Mr Smith has refused to speak about his actions, except to say that the publicity was causing him "massive distress".
Following death threats, he has now installed security cameras at his home.