Authorities believe the animals are slaughtered to provide meat on the black market.
The latest horse, Bonita, found in Northwest Miami-Dade on Sunday morning by its owner, had been set alight after being butchered.
The butchery began on January 11. Police are investigating and the Humane Society of the United States has offered a $US2500 reward for information leading to the arrest and conviction of those responsible.
The South Florida SPCA says it is working hard with authorities and other agencies to address the serious issue.
It warns that horses are often given steroids and medicines that are not appropriate for humans to eat.
Its website carries the harrowing tale of Ivonne Rodriguez, of Miami, whose horse, Geronimo was one of the earlier victims.
Geronimo, a paint horse, was stolen from his pasture on February 27.
"A police report was filed with Metro Dade Police Agriculture Patrol. The officer who wrote the police report told me that he didn't want to alarm me but the horses are being stolen for their meat. Needless to say I was alarmed and in disbelief," Ivonne said.
"Sadly to say, my horse was found on March 5 in the field across from where he was last seen, 200-300 yards inward.
"He had been tied to a palm tree and slaughtered right there.
"You can just imagine my dismay. Geronimo was my pride and joy and my dear companion.
"It was difficult to find him because his body was covered with palm frowns. It wasn't until someone stumbled on his head that he was found.
"Jeff Burnside, from Channel 6 NBC, interviewed me earlier that morning and we wanted to make sure this was made public, in the hopes that I could have him returned to me safe and sound.
"Later that day he met me again on the site where Geronimo was found. He met officers of the Ag Patrol as well as Richard Couto from the South Florida SPCA.
"This is something that needs to be stopped. My horse was very well taken care of and I loved him dearly. He was a member of the family.
"I don't want his death to be in vain."