Some 1400 Victorian dairy workers are walking off the job in what organisers say is the sector's largest strike in memory.
Staff will be a no show for the first shift at 13 regional and metro sites across the state and are expected to be absent for 48 hours as they demand better pay and conditions.
Four major dairy producers are being affected by the action, with Fonterra, Saputo, Lactalis and Peters the names behind national brands including Western Star butter, Cracker Barrel cheese, Peter's Ice cream and Perfect Italiano.
However the companies have moved to reassure customers there will be minimal production disruptions.
The United Workers Union says there has been a failure to offer the striking process workers fair wages and conditions amid rising living costs.
"Workers who put up with wage increases as low as 2.5 per cent a year during the pandemic are saying they deserve a cost-of-living wage increase," national secretary of the United Workers Union Tim Kennedy said.
"These workers are fighting for safe, secure jobs in regional communities, where almost every dollar they earn goes back into those communities."
Despite producers saying supplies will be maintained, Mr Kennedy said consumers can expect to see an impact at supermarkets.
Along with the wage increase, workers want personal leave accommodating their 12-hour shift pattern and community service leave for helping in natural disasters.
Fonterra director Rob Howell told AAP on Monday the company had a "fair and reasonable offer" on the table, with a minimum 10.5 per cent salary increase over three years and more leave options.
Fonterra would ensure there were minimal disruptions from the industrial action, he said.
"Our farmers will continue milking and we will be doing everything we can to ensure that their precious, perishable milk can be collected and not wasted," Mr Howell said.
Saputo was committed to resolving outstanding items with union representatives "amicably and swiftly", operations director Gerard Lourey said.
The company is also putting contingency measures in place to minimise disruptions.
Lactalis said its priority was working with farmers, who were at the peak of the spring milk season.
A Peters spokesman said the company was surprised by the "unnecessary union-led blanket action" and negotiations have continued in good faith.
