WELLINGTON, Sept 6 (Reuters) - New Zealand's Fonterra Co-Operative Group Ltd, the world's biggest dairy exporter, said on Wednesday it would aim to improve margins by supplying a new range of nutritional foods for other companies to sell under their own brands.

The product range, called Nutiani, would comprise powders and drinks with such attributes as helping to mitigate stress, improving mobility and managing body weight, Fonterra said.

"The Nutiani brand has flexibility to help us grow in non-dairy specialties, such as our probiotics portfolio, which is not constrained by milk supply or linked to the commodity markets," said Dan Luo, acting director of the Fonterra division undertaking the project.

Fonterra has long turned much of its milk into whole milk powder for export to Asia, especially China. But after more than a decade of strong growth, New Zealand's milk production is slowing and the number of dairy cows falling.

Higher regulatory costs and changing agricultural land use, driven by policies for fighting global warming, are behind the change. Noting this, Fonterra has previously said there were opportunities to be more selective in what it did with its milk.

Luo said the new product range was part of the company's strategy to create more value from milk through dairy innovation and science.

"It drives stronger focus on both the higher margin and more (a) differentiated portion of our portfolio," she said in written replies to questions from Reuters. "Nutiani will go beyond just promoting our ingredients. For example, it will promote our IP (intellectual property) through formulations, patents, trademarks and other brand assets."

Fonterra will market the products to other food companies, not directly to consumers or retailers. (Reporting by Lucy Craymer; Editing by Bradley Perrett)