We reported on market speculation in relation to such a deal last week.
Moy Park says it will focus on the manufacture of poultry feed at its feed mill in Randalstown.
David Gibson, that group's director of agriculture, said Moy Park has undergone significant growth over the past two years and is now processing over five million fresh chickens per week.
He said the company now plans to optimize its poultry feed mill capacity in support of the poultry business involving investment of around £1.2m in 2016.
McLarnon’s ruminant business, continued Gibson, is a natural match with Thompson’s expertise in that segment of livestock production.
Thompson’s CEO, Declan Billington, said: “Given Moy Park’s focus on poultry expansion, and our long-term relationship with them, it seemed only natural that we would come together to support the growth prospects of the McLarnon ruminant business. “