Dogo Argentino are sometimes used for illegal dog fighting.

"..The first dog used for pit fighting in Argentina was the ‘Córdoba fighting dog’, which is now extinct. This fierce guard dog showed a willingness to fight to the death and high pain tolerance, even when mortally injured.

However, after several years, breeders realised this dog was unstable as it often turned on its own pack members. Therefore, in the 1920s, physicists and brothers Drs Antonio and Augustin Nores Martinez created the ‘Dogo Argentino’. Based on its cousin from Córdoba, the Dogo is a cross between mastiffs, bull terriers and bulldogs. The Argentine doctors chose these breeds because the breeds showed courage and tenacity during pit fights they had witnessed as children.

The official kennel club of Argentina describe the Dogo as a “very strong, muscular dog with powerful jaws with large teeth”. It has short white fur, occasionally with markings around the eyes and can reach up to 70cm in height.

Jose Miguel Rivero Garcia is a breeder in Argentina. He says that “despicably, Dogos Argentinos are used in fights, which occur in clandestine places that only a specific few know about and normally involve large sums of money”. He added that although he had not personally witnessed a pit-fight, he had been approached as a breeder to provide dogs for them..."

source: http://www.argentinaindependent.com/socialissues/urbanlife/amores-perros-dog-fighting-in-argentina/