Distressing video shows a Staffordshire bull terrier chained up and forced to run on a treadmill.
It has no way of escaping so has to keep running despite becoming exhausted, with its tongue hanging out.
Breeders use this as part of training to make their dogs killers, forced to fight others to the death as a cruel spectator sport.
The RSPCA released footage showing the tactics used, saying the sport is ‘rife’, despite being illegal for almost 200 years.
In just four years, they received almost 8,000 reports of dog fighting in the UK.
Last month, a group who trained and bred dogs for fighting in Lincolnshire and Wales were convicted following a trial.
John Knibbs, 55, was found with eight dogs at his home in September 2017.
Investigators found video and photos on his phone showing dogs being trained and forced to fight, as well as messages talking about ‘crushing of bones’.
Many of the dogs forced to fight are banned breeds such as pit bull terriers. It means that even if they are rescued, they cannot be rehomed and have to be put down – a practice the RSPCA is opposed to.
One dog which did have a happy ending is Kali, a staffie found cowering in a garden in Hertfordshire in March 2017.
She was covered in scars, open wounds and bloody bite marks. RSPCA officers traced her owner – who was later convicted at court of animal welfare offences – and she was taken into care for treatment and rehabilitation.
Georgina Arnold and boyfriend Owen Gray, from Yaxley in Cambridgeshire, read about Kali’s story in the local newspaper and adopted her.
‘We love her so much, we couldn’t be without her now,’ Georgina said.
‘She has scars and is missing teeth so she has been through a lot. But she is so kind, she is like a teddy bear, there’s not a bad bone in her body. I’m just glad that she’s safe now and she’ll never have to know fear or cruelty again.’
RSPCA inspector Mike Butcher said: ‘It’s incredible that Kali has recovered from her awful ordeal and gone on to a loving new home where she’ll be safe and cared for.
‘Sadly, the reality is that for many dogs, this will never happen. Dogs who win fights are prized and are often treated like kings. But those who refuse to fight or lose are often abandoned or barbarically killed.
‘The dog fighting world is a dark and frightening place. But it could be happening in an inner-city warehouse next door to your office or on a rural farm in your quiet village.’
He urged anyone with concerns to contact the RSPCA on 0300 1234 999.
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