The deal for a2 Platinum production is for a minimum five-year term, with a rolling three-year term after the first two-year period.
The companies say that current production volumes will stay the same, but provisions have been made allowing for increased scale to meet medium-term market demand.
Geoffrey Babidge, managing director and CEO of a2MC said that the deal also gives the companies the flexibility to assess new market or product opportunities as they arise.
Both companies say they will continue to work closely to forecast demand and supply for a2 Platinum, particularly with respect to the evolving regulatory environment.
John Penno, managing director and CEO of Synlait, said that the company has assessed its production commitments to all its customers, and can meet all production needs into the foreseeable future.
a2MC said that the deal was good news for its a2 milk suppliers, especially as many have adapted their farm businesses to supply a2 Milk.
The term of the extended and reworked agreement gives farmers increased certainty in an uncertain time for the dairy industry, a2MC added.