David Farley, chief executive officer of Australian Agricultural Co., told The Age, a Melbourne newspaper, the remark was "tongue in cheek."
During a 30-minute presentation at a conference in Adelaide, Farley described a slaughterhouse his company plans to build in Darwin. He said the plant is intended to process "old cows," converting them into inexpensive meat.
''So it's designed for non-productive old cows -- Julia Gillard's got to watch out,'' he said.
InDaily, a news Web site, said those at the conference laughed at the line. But Julie Collins, minister for the status of women, said the remark was "totally unacceptable."
"Mr. Farley and those who laughed along with him should take a good, long, hard look at themselves," she said.
Gillard, 50, is the first woman to serve as Australian prime minister, a post she has held since 2010. She is a member of the Australian Labor Party.