Union secretary, Graham Smith, says the visa guarantees overseas workers their weekly wages, at a time when local workers are having their working hours cut due to a shortage of livestock.
Mr Smith says 260 local workers at an abattoir at Naracoorte in the state's south east are struggling to support their families.
But he says 25 Chinese workers by contrast are receiving full pay, as required under current working visa arrangements.
“We've got meat workers who traditionally get stood down at this time of year - I mean Naracoorte meat works had a shut down of about 7 weeks last year, where they didn't work at all. But the Chinese are guaranteed earnings on a minimum annual basis where the Australian workers are not. And let's not forget either that the basis of this 457 visa is to fill skills shortages - they haven't even got any work!” Mr Smith said.