About 100 people are to lose their jobs with the closure of the Elanco manufacturing facility in Sligo town.
The parent company, Elanco Animal Health, based in the US, said "unfortunately, cost-reduction initiatives at Sligo, including a restructuring last year, have not been sufficient in establishing a competitive business model for the facility".
Staff at the Sligo plant in the Finisklin Business Park manufacture a range of veterinary vaccines, mostly for the European market.
The company said the majority of employees will be made redundant in the first quarter of this year while a small number will support product transfer and decommissioning activities throughout the year and into next year.
