Australians might feel differently about meat consumption if they likened farm animals to their beloved dogs and cats.

That's according to Chris Delforce, creator of new documentary Dominion, which has led to thousands rallying in the Melbourne CBD to protest animal rights and raise awareness.

The crowd, dressed in black, planned to march from the State Library of Victoria to Federation Square on Saturday, with a truck broadcasting confronting footage from Delforce's film.

"We're seeing pigs in gas chambers, it's the most common way that pigs are stunned now in slaughterhouses all over Australia," Delforce told AAP at the start of the peaceful rally.

AAP

"And every pig who goes into that chamber screams and thrashes and fights with every last breath."

"We're trying to show, from the individual level, what these animals are going through."

"Pigs are just as smart, if not smarter than dogs. They can feel joy and pain and love, and everything that dogs and cats can feel."

Many at the rally could be seen shedding tears as speakers told of scenes they had witnessed in slaughterhouses.

"It is a disgrace that we perpetrate so much violence against the most innocent and vulnerable beings on this planet," activist James Aspey told the crowd.

The event is the start of a six-month campaign to shine a light on the meat, dairy, egg, clothing and entertainment industries.

Three marches have been planned for Melbourne and Delforce has pointed to other actions, including lock-ins at piggeries and disrupting farm operations across the country.