Forty-six heifers died of dehydration at the Queensland government-owned Swans Lagoon research facility, about 80 kilometres south-west of Ayr, in May last year.

Police found no evidence of criminality, so they did not recommended any charges. However, they blamed the incident on the negligence of a staff member who accidentally locked the cattle in a paddock without access to water.

The staff member, whose name was removed from the report, closed and chained a gate between two paddocks to prevent the cattle he was mustering from returning, but forgot to tell colleagues.

Injuries to another staff member meant a scheduled "water run" was not conducted and the cattle were left without water for 12 days.

Detective Sergeant Mark Hogenelst, the officer in charge at the Stock and Rural Crime Investigation Squad in Charters Towers, found that in addition to the 46 deaths, many surviving cattle also suffered horribly.

"An inspection of the remaining live cattle showed barbed wire cuts to their dewlap areas, demonstrating how they had been trying to push through other boundary fences in the paddock to seek water," he said.

"If the gate was merely closed without being chained, these cattle would have easily pushed through to available water."

Detective Sergeant Hogenelst found the deaths occurred "due to an unfortunate set of circumstances and poor judgement on behalf of (two staff members)".

"I do not believe that any person has acted maliciously or intentionally to kill these cattle, and as such, not all of the elements for each offence can be satisfied, and I believe no offence has been committed," he said in his report.

The report was delivered to the Department of Agriculture and obtained by Fairfax Media under RTI legislation.

Agriculture Minister John McVeigh, who ordered the matter to be referred to the police, said the staff member involved in the incident no longer worked for the department.

"In addition to the police investigation, the department undertook an independent review of management practices right across departmental properties that handle animals," he said

"Following this review, the department has amended operational procedures to ensure this incident is not repeated."

RSPCA chief prosecutions inspector Annabel Buchanan said she generally agreed with the decision not to prosecute, but she disagreed with the reasoning behind that decision.

"You don't have to act maliciously or intentionally to kill an animal to face a charge of a breach of duty of care," she said.

"(Detective Sergeant Hogenelst) literally, in one fell swoop, said because they had not acted maliciously or intentionally to kill the cattle, he's pretty much wiped out charging [them] under section 17 and section 18 (of the Animal Care and Protection Act 2001) and the criminal code."

But Ms Buchanan said it appeared the facility had acted in good faith.

"You can make a mistake and not be subject to a charge if you've taken steps to provide appropriate accommodation, food and water," she said.

The Swans Lagoon property was sold in March to Peter and Brenton Malpass for $7.2 million.

"All northern beef research is now conducted at Spyglass beef research station via Charters Towers, where improved management procedures are in place," Mr McVeigh said.