Staff were told of the final decision yesterday morning, following a consultation period.
Chief executive Willie Wiese said the decision was made "with a heavy heart".
While the 600 affected staff would be offered the opportunity to apply for redeployment at Alliance’s other processing plants wherever possible, the decision meant the "vast majority" of employees would be made redundant.
"Our thoughts are with our people and their families affected by the closure of this plant. Smithfield has been a familiar presence in the region for almost 140 years and we know this decision will impact the Timaru community and South Canterbury," Mr Wiese said in a statement.
Timaru Mayor Nigel Bowen said the closure was a significant blow not only to the hundreds of families directly affected, but the whole community.
"It’s really important that the community now wraps itself round the people affected and ensures we help them every way we can," he said.
"We’re a district of opportunities, and our economic development body, Venture Timaru, will be working closely with the South Canterbury Chamber of Commerce to identify local businesses needing staff and linking them with those seeking employment.
"Our Community Development team has also met with all the non-governmental support agencies in town to ensure they are aware of the issue and can be co-ordinated in their response.
"We’ll also be helping by ensuring that there’s a single place people can go to access advice and [the] support resources they need," he said.
A series of drop-in sessions covering the likes of CV writing, budgeting, managing redundancy, applying for benefits and health and wellbeing had already been organised while a jobs fair to match affected workers with about 40 local employers will be held on November 5.
Alliance has blamed declining sheep processing numbers as a result of land-use change, which had resulted in surplus capacity in its plant network for the closure.
NZ Meat Workers Union southern region senior organiser Bill Watt said the announcement did not come as a surprise, despite the number of very good submissions made during consultation.
The mood yesterday was one of uncertainty; while there were some jobs around, there were "certainly not 600-odd". He also cited the impact on the wider community, having heard the plant injected about $50million into the local economy.
He said successive governments needed to start understanding that if the country’s export earnings kept reducing, "where do we as a country go?".
Governments seemed to have "shrugged their shoulders" at overseas buyers buying "hundreds of thousands of acres" of prime farm land to plant in trees and then "disappear". If that continued, then more plant closures were likely, he said.
