Westland Milk Products has bought the remaining 25% stake that it did not own in the EasiYo yoghurt maker.
Westlake says wholly owning the company will give it a greater foothold in the value-added end of the milk product market.
The stake was acquired from Kathy and Len Light, who established the business in 1991.
EasiYo has sales of $30 million per year with three quarters of its products exported, mostly to Britain and Australia.
