Bellamy, who departs on 31 January, will head a new worldwide initiative called Dairy Global Platform - an alliance to promote dairy products as healthy and nutritious.
He has worked at the MDC for ten years, initially as head of R&D, before taking up the role of chief executive five years ago.
"The council is sorry to lose Kevin's tremendous input to the MDC, but recognises the importance of this new role to Britain's, as well as the world's, dairy farmers," said Brian Peacock, MDC chairman.
Bellamy said: "Despite significant amounts of research saying milk and dairy are good for you, it still gets a bad press.
"Providing a platform to support all activity across the world will give organisations like the MDC much better access to the information it needs to communicate as effectively as possible with consumers."