Miami (AFP) - Workers are shown beating, kicking and stabbing cows with steel bars at a Florida diary, in a video released by an animal rights group that has been viewed thousands of times.

One of the workers seen mistreating the cows in the hard-to-watch video has been fired and the others suspended from their jobs, said Brittny Krause, a spokeswoman for the Florida Dairy Farmers, an association with 130 dairy farms as members.

The sheriff's department has opened a criminal investigation.

Animal Recovery Mission, a Miami-based protection group, said the video was taken in August by an activist working undercover at the Larson Dairy Farm in Okeechobee, Florida.

The edited, five-minute-long video shows several workers beating and kicking the cows.

They also hit them with a steel construction rebar, jamming their heads and sides to force them to stay in the milking stall.

"The short metal rods pierce and penetrate the cows' bodies," a voiceover says. "New mothers are punched in their sensitive udders."

In a statement, ARM described cows falling to the ground as a result of the beatings.

"The cows were witnessed to be maliciously beaten repeatedly for no apparent reason and deep wounds and untreated abrasions were evident," it said.

Okeechobee County Sheriff Noel Stephen said he had opened an animal cruelty investigation against Larson Dairy.

"I believe that there will be criminal charges that will be forthcoming upon the completion of this investigation," he told a news conference.

The dairy's owner, Jacob Larson, said he was "saddened and appalled" by the behavior shown on the video.

"The unusual use of force is simply unacceptable on our dairy or on any other farm. We have strict protocols involving animal care and clearly the behavior shown in this video goes against everything we stand for and will not be tolerated."

Animal Recovery Mission founder Richard Couto told AFP that mistreatment of cows is common in dairies in the US and around the world.

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"But we don't usually see steel rebars being stabbed into animals like that, so that is different," he said.

The Publix supermarket chain, the state's biggest, said it has suspended orders from the Larson Dairy Farm.

The video was posted Thursday and by midday Friday had been viewed more than 17,000 times.