Injections of the Class A narcotic make the animal junkies extra fierce and aggressive, as they are forced to go through detox.
Four in every 10 dogs accepted each year at one animal shelter are addicts, owner Ian Robb said.
“Dogs are trained to attack police if their owners’ homes are raided. Dealers buy a fake uniform and teach the dogs to attack someone wearing it,” the Mirror quoted him as saying.
Robb, 64, who runs the Angus Dog Shelter, in Forfar Scotland, takes in 70 to 120 animals a year. Some have been given cannabis, but most addicts are on heroin.
Two Staffordshire bull terriers – a favourite of the drug bosses – were put down because they were “bouncing off the walls”, he said.
“A dog on heroin will run around and be completely manic. If you approach it you will definitely get bitten,” Dog expert Lesley Connelly said.