Affco is appealing an Employment Court ruling that it unlawfully locked out Wairoa workers during collective bargaining talks.
Affco was the first employer to test amendments to the Employment Relations Act, which let firms opt out of multi-employer agreements and removed the duty under good faith bargaining for both sides to reach an agreement.
In February the Employment Court ordered Affco to reinstate 160 Wairoa union members to their normal shifts and recognise seniority after they were locked out for almost six months.
It said they were locked out unlawfully without the required notice and the company undermined the collective bargaining process by sidelining the Meat Workers Union.
The dispute started when the NZ Meat Workers Union and Affco failed to renegotiate a collective agreement that expired in 2013.