The women said the pit bull started biting at one of the horses, Ruby.
"That's when I heard Vanessa. She screamed," Vanackeren said. "The dog was actually grabbing on to her foot and pulling her out of the saddle and towards the ground, and that's when she hit the tree."
"I crash into it and I hit the ground, and I see a dog's face at mine," Farrish said. "And I raise my right arm to cover it, and I feel pain in my hand."
The dog then turned its attention to the other horse, Nova, biting her several times, the women said.
"It relentlessly continued to attack us," Vanackeren said. "This wasn't a quick attack. It lasted over several minutes, and the dog got more and more aggressive."
"The dog was jumping up and attacking her belly," Vanackeren said of the horse. "She's got several stitches and staples trying to hold it together."
Farrish has a concussion, a bitten hand and bruises all over her body.
"I was terrified. I've never been attacked by a dog," she said.
Farrish owns a pit bull herself and said she has nothing against the breed.
"It's not the dog, it's the one who owns them," Farrish said.
The women shared their story for other riders to be aware. The family said it is working with Pierce County Animal Control on the case.