One bull's horn was broken when it was forced off the truck while another had water thrown over it to make it stand up.
The bulls were hog-tied, including one that had its two front legs stamped on before six men held it down while another slaughtered the bull after two attempts to slash its throat.
Labor MP Kelvin Thomson, a vocal opponent of the live animal trade, said the Department of Agriculture had to cancel or suspend export licences to make a serious difference.
"The department has to apply real penalties, not the Mickey Mouse ones that have been handed out so far, or this unacceptable cruelty will continue," Mr Thomson said. "It has the power to take the export licence off this exporter and it should use it."
Activist group Animals Australia also believes a severe penalty should be handed down.
"The Australian community will be mortified to see once again vision of Australian cattle being dragged, pushed, kicked and brutally slaughtered in direct contravention of Australian live export regulation,” group legal counsel Shatha Hamade said.
“The only deterrent is for those sanctions to actually be enforced on those exporters, either by a loss of licence or a suspension of trade or a loss of trade into that particular area for the importer.
“The regulations themselves are clearly not doing the job."
Australian regulations require exporters only sell to approved abattoirs.
Animals Australia investigators filmed the bulls in Mauritius City between October 13 and 16 after hearing of concerns about the treatment of animals
It gave the footage to the department two weeks ago, and it is now investigating the incident.
"Investigations take as long as needed to ensure a fair and accurate outcome is reached," the department said.
"No regulatory system can eliminate the issues it has been put in place to guard against.
"What is important is how we address these incidents, and that exporters are held accountable."
Animals Australia alleges Perth-based exporter International Livestock Exports shipped the animals to Mauritius.
International Livestock Exports referred Fairfax Media to its lawyers at Clayton Utz, saying ILE director Michael Stanton “was on a boat in Broome" and unavailable for comment.
A spokesperson for Agriculture Minister Barnaby Joyce said the department would find out how the mistreatment occurred and discuss with the people involved how it could be avoided.
"No one supports animal cruelty, least of all Australian farmers and exporters," the spokesperson said. "These investigations aren't about shutting down the trade, they're about policing it – the way an officer polices the roads.
Prime Minister Tony Abbott said last week the government was unmoved on its stance on live exports and any rule violations would be addressed.
"We support the live export industry, I want to make that absolutely crystal clear," Mr Abbott said.
"It is a good industry for our country, it is a good industry for our farmers and it's a good industry for our partners around the world.
"The existing system is designed to ensure that animals are not mistreated."