The RSPCA has criticised a decision to redact information about heat stress management and other animal welfare concerns in reports from Australian live export ships.

The heavily redacted reports were released to the RSPCA by the Department of Agriculture and Water Resources under freedom of information laws, after being delayed for six months.

Video footage – which is referred to heavily in the reports as proof of adequate animal welfare conditions – was not released, with the department telling RSPCA it would take too long to collate the footage.

In a statement to Guardian Australia, the department said: “The publication of the full reports would make business information, commercial-in-confidence information and personal information public.”

The independent observers’ reports detail eight live export voyages undertaken between April and June in 2018, after agriculture minister David Littleproud ordered that independent observers be placed aboard each live export ship following damning footage released from the Awassi Express.

That footage has since been called into question, with Littleproud asking the department to investigate whether money was paid to whistleblowers who released the footage to Animals Australia. Animals Australia has stood by the veracity of the footage.

All independent observers were veterinary officers with the department.

The eight voyages operated under a reduced stocking density and most took place after the release of the McCarthy review into deaths caused by heat stress on live export ships.

All eight reports obtained by RSPCA state that the observer noted “no significant noncompliance issues” on board.

However, most reported lambs being born on board, which is a breach of the Australian Standards for the Export of Livestock (ASEL).

One report mentioned a sheep being slaughtered for consumption by the crew.

All reports mentioned some signs of heat stress such as panting or open-mouthed breathing but none reported significant deaths from heat stress. In other cases, sheep died from enterotoxaemia, a type of blood poisoning, or were euthanised due to infected shearing wounds.

Most reports mentioned that extra space on board, created by a reduction in allowed stocking densities, meant up to half of all sheep in a pen could lie down at any one time and sheep had good access to food and water.

Some ships, like the Al Messilah, which was penalised for a the mass deaths of 3,000 sheep in 2016, had since installed fans and windows to improve ventilation and reduce heat stress, but still reported a number of sheep experiencing heat stress. That report also noted some sheep were dragged by their front leg by crew with a “general lack of experience in animal handling and droving”.

However information about heat stress risk assessment (HSRA) plans was redacted.

The RSPCA senior policy officer Jed Goodfellow said the reports and images that were released showed continued animal welfare concerns despite being taken when the live export industry was “on its very best behaviour”.

“Perhaps even more alarming than the evidence of continued suffering on board these ships, are the pages and pages of redacted information, consistently where management of animals and heat stress on board are discussed,” Goodfellow said.

“The department has also flat out refused to release the video footage taken on board the vessels, which is the only real means of truly appreciating the animals’ behaviour and condition during the high heat-stress periods.”

A damning report released in October found the department was “lacking” as a regulator because it also acted as a promoter of the live export trade.

The department said it had moved to provide “unprecedented transparency on live animal export voyages”.

Labor has pledged to phase out the live export of sheep if it wins government.

Submissions on a review of the heat stress risk assessment model close on 1 March.