Some 550 workers at Grampian Foods plants in Sandycroft and Llangefni, both in North Wales, struck on Monday against a pay freeze.
Pickets were well attended, the mood was very optimistic.
Passing drivers were hooting support for the strikers.
Paddy McNaught from the T&G union said that the average hourly rate at the plant was just £5.55 an hour. “How can people live on those wages? The pay freeze here has actually meant a pay cut as shift allowances have been cut,” he added.
Despite imposing a pay freeze on the Sandycroft and Llangefni workers, the company has given a pay increase to workers at their Cambuslang plant in Scotland.
The workers plan another one-day strike on 10 November.