Fonterra chief executive Theo Spierings says it will take a couple of weeks for the price of units in the co-operative to settle after their explosive start on the NZX yesterday.
By close, the units were trading at $6.85, after debuting on the market at $6.66 - a 21 per cent premium to their $5.50 issue price.
Spierings said it was clear from the outset that there would be strong demand for the units and yesterday's price spike probably reflected demand from investors who had missed out during the book-building phases.
"But this is only five minutes," he said after the stock officially listed. "For me it's a matter of where we will be in two or three weeks."
The units do not confer a direct voting interest in Fonterra but their trajectory is expected to be based on the performance of the co-operative.
Interest in the units was such that brokers had to heavily scale back investor applications during the book-building phase of the offer.
The units form an integral part of Trading Among Farmers (TAF), which has two elements.
The Fonterra Shareholders Market, which also started yesterday, will allow farmers to trade Fonterra shares exclusively among themselves.
The second part, the $525 million Fonterra Shareholders Fund, will give investors access to Fonterra's dividend flow.
Fonterra priced its units at $5.50 apiece, the top end of Fonterra's desired range, with 42 per cent of the fund being sold to overseas investors.
The scheme is aimed at reducing Fonterra's redemption risk, which is when the co-operative has to pay out shareholders when they exit the sector.
At $5.50, the units are expected to yield 5.5 per cent a year.
The unit's debut coincided with the official opening of Fonterra's new $500 million milk processing plant at Darfield, near Christchurch.
The plant will process 2.2 million litres of milk a day into whole milk powder bound for Southeast Asia, China and the Middle East.
Darfield is Fonterra's first new greenfields site in 14 years.
Fonterra chairman elect John Wilson said the launch of TAF and the opening of the new Darfield site symbolised the strong future for the farmer-controlled co-operative.
He said TAF would give Fonterra a stable capital base and confidence to invest in the most productive areas to add value, grow the company's brands beyond existing positions and compete strongly in the fastest-growing dairy markets - Southeast Asia, Middle East and China.
"For the first time in Fonterra's history, farmer shareholders are able to buy and sell shares among themselves on the Fonterra Shareholders' Market," he said. "At the same time, members of the public can now gain exposure to a New Zealand success story and the world's largest dairy processor by buying units in the Fonterra Shareholders' Fund."
Darfield processes about 2.4 million litres of milk in a single day. Once a second, larger drier is completed next year, its capacity will go to 6.6 million litres.
A registered volume provider will facilitate trading in the farmers market but can also exchange shares for units.
Shane Solly, head of equities at Mint Asset Management, which holds units in the fund, said it was a "stunning" debut. "It's a great, great outcome for Fonterra, farmers and unit holders," he said.
NZX chief executive Tim Bennett said the listing was an important milestone for the market and economy and might prove to be a precursor for other listings, outside those already flagged by the Government in the form of the state-owned power generators.
"The investment bankers are very excited by the pipeline," he said.
He said the strong demand for Fonterra reflected in part a change in New Zealand savings patterns.
Fonterra, he said, was "the only truly global champion that New Zealand has".