Dutch food producer Vion NV, which employs 13,000 people in 38 sites around the UK, is to sell its UK operations.
The group runs abattoirs and processing plants and has said it is confident it will be able to sell the UK sites.
But the company was forced to close its pork processing unit, Hall's of Broxburn recently, along with other setbacks.
Both the NFU and the Farmers' Union of Wales expressed concern at the potential effect of the withdrawal and what it could mean for meat production and processing in the UK.
Vion is a major purchaser of Welsh Lamb and beef and as well as employing around 13,000 full time equivalent employees across the UK, 3,491 are employed in their four sites across Wales including Anglesey, Merthyr Tydfil and Sandycroft, Flintshire.
FUW livestock, wool and marts committee chairman Dafydd Roberts said: "This announcement will result in uncertainty for the farming industry in Wales who need to know that they participate in a stable supply chain."
The food group employs 3,491 meat and poultry workers in Wales.
"This uncertainty comes as farmers are already facing a winter with high input costs due to a poor growing season. The FUW stresses the need for Vion to provide stability and certainty whilst divesting of its operations in Wales, with no disruption to the supply chain or loss of jobs to the Welsh economy."
Roberts, a beef and sheep farmer on Anglesey, said the move was disappointing, particularly as there had been hopes for further investment at the company’s operations on the island. “If they were to close it would be a blow for the whole Welsh meat industry.
“If we lose one of the big ones like Vion then others might take advantage of the farmers. We are quite disappointed they are selling up because we were told they would be improving Anglesey.”
Roberts added that the options available to red meat producers in Wales in terms of processing facilities are limited. "The Vion abattoir and processing plants are important elements of the supply chain, enabling farmers in Wales to access supermarket outlets for quality Welsh beef, lamb and poultry products.
"It is essential for the industry to ensure that these routes to market are secured for the long term and the FUW looks forward to hearing of a positive outcome to the Vion UK sales negotiations."