Dangerous dogs are being bred by young men as an asset in drug deals, debt collection and for their gang image, according to new research.
More young men were using mastiffs, pit bulls, akitas and other aggressive dogs as a "commodity" for security and making money in gangs, the Middlesex University study found.
The study found the most aggressive dogs could be sold for more than £400, with owners building up their pet's muscles with vitamin supplements and even injecting them with steroids for fights.
The study, which will be presented to the British Sociological Association annual conference today, also found there has been a rise of 551% in hospital admissions for dog bites since 1991.
More top news
Migrants desperate to reach Britain from Calais have told how making the dangerous journey is their "last chance".
Malaysian Airlines flight MH370 vanished more than a year ago carrying 239 people on board. Here is a look at the key events since.
Investigators have released images of two more people they wish to speak to about the Hillsborough tragedy.