Rather, they are on individual contracts the union said they were "forced" to sign in order to return to work at the start of the season.
But Affco said it was complying with the terms of the ruling.
Central to the Employment Court ruling was that meat workers are deemed to be in continuous employment even though they are laid off at the end of the season and rehired for the new season.
That decision overturned several decades-old cases - known as the Alliance case and the Richmond case - that held there was no continuity and had been cited as precedent in a number of cases over the years.
Rowan Ogg, Affco's director of operations, said that law was set primarily under the Richmond case about 30 years ago and upheld in a number of subsequent cases. With that in mind, the Employment Court's decision was "rather a surprise".
He said the decision would be challenged in the Court of Appeal "and in the interim we're complying with what the court has said".
Mr Ogg said Affco's issues with the expired collective contract included conditions that had not changed in 50 years and were no longer appropriate in an industry "looking for far more flexibility".
The Employment Court found the Alliance and Richmond rulings were also outdated, saying the nature of employment generally and its regulation "have changed significantly over the past 30 years or so in New Zealand, including at times when a number of the cases, which concluded that seasonal meat industry work was discontinuous, were decided".
"To maintain, as Affco does, its recent current arrangements reflect those traditional patterns ... is an artificial and strained account of the reality ... under current employment law."
The case covered workers at Affco's Imlay works along with those at the Rangiuru and Manawatu plants. The company had accepted any finding would cover all eight of its North Island plants.