The two-year-old underwent emergency surgery and needed 200 STITCHES in his face following the horror.
The little lad has since endured further operations but will still be scarred for life when he finally goes home.
His mother, Lisa Mann, 23, of Brockworth, near Gloucester, has spoken of her shock at seeing her bloodied son in hospital and warned parents of the dangers of allowing children around dogs.
She said: "I thought he was going to die. He looked in so much pain.
"All I wanted to do was pick him up and hold him, but I wasn't allowed.
"It was the worst feeling ever."
The attack happened on Saturday when Joshua was at his grandparents' farm in Andoversford, near Cheltenham, Gloucs.
Miss Mann said: "Joshua was stroking the sheep dog, Rossie, when he jumped up and latched on to his face. Rossie pulled him to the ground and wouldn't release him.
"His dad and others ran over and started punching the dog to get him to let go."
Joshua was taken to the Gloucestershire Royal Hospital, where he underwent two operations to repair the damage to his face.
BloodThis morning he underwent a third operation.
Miss Mann said: "When I turned up, seeing the injuries for the first time, I nearly passed out with the sight of blood.
"The size of his face was unreal, the way it had swelled up."
Describing Joshua's injuries, she added: "You could see right through his cheek to his teeth, the cut went through to the inside of his mouth.
"He also has wounds to his neck that were millimetres from the main artery carrying blood to the brain.
"He has scars all over his back, the back of his head and behind his ear."
The dog has since been put down.
Miss Mann today warned parents to take care around all dogs, not just those seen as dangerous breeds.
She said: "You just need to be more aware, if a dog is not brought up around children, if they're not used to them, they can just go.
"People naturally think it's pitbulls, rottweilers and the other dangerous breeds, but this was a collie. It's not usual that a collie would do this, but he wasn't brought up with children and snapped.
"If a dog is not used to the attention, it's just not worth it. You should just not have them in the same room."
The RSPCA warned parents that no matter how kind and trustworthy a pet may be, any dog can potentially pose a risk.
Spokeswoman Jude Clay said: "The RSPCA believes that a dangerous dog is not defined by breed.
"We believe that a lot of the issues related to dangerous dogs could be tackled with the introduction of a properly enforced dog licence which would raise funds to plough into problems such as injuries from dog bites, dog control and responsible pet ownership."
She added: "Our thoughts go out to the family concerned at this time and we wish the boy a speedy recovery."