Fonterra's constitution will eventually have to be re-written to allow for overseas investment if the co-operative ever wants to be a truly global player, a leading academic says.

Fonterra yesterday revealed it had gained NZ$270.7 million in new equity through the purchase of additional shares offered to its farmers late last year.

Waikato University chairman of finance Stuart Locke said the fact that Fonterra had only been able to raise NZ$270 million meant overseas investment in the co-operative was now inevitable.

"If the are to be a major player in the world market they need a lot more equity," Locke said.

Locke compared Kraft's US$26 billion buyout of Cadbury with the farmers' NZ$270.7 million share purchase, saying it paled in comparison.

"If Fonterra is operating on that sort of stage we are talking massive amounts of money, and that's beyond the scope of 10,000 shareholders."

He said Fonterra was executing a "gradual program" over the next three to five years to encourage farmers to begin trading in dry shares, and then eventually accept foreign investment in the co-operative.

Locke added that it was important that farmers retained control of Fonterra.

"The constitution could be amended to the point where 40 per cent of the shares can be traded amongst non-farmers, so the farmers always own 60 per cent ... the majority."

Federated Farmers chairperson Lachlan McKenzie said farmers would never allow Fonterra's constitution to be amended to allow for overseas investment.

"[Fonterra] understand the benefits of a company being owned by its supplying members," McKenzie said.

"That then ensures that the benefits of profits the company makes flow back to New Zealanders for the benefit of New Zealand Incorporated."

Locke said the effect of Fonterra's profits heading offshore would have little impact on the New Zealand economy.

"It's just a financial flow."

McKenzie said the $270.7 million raised by the co-operative in its share offer was "within the bounds of expectation".

"There was never a hard sell by Fonterra," he said.

McKenzie said the share offer was as much about providing stability in the co-operative's share structure as it was a capital-raising exercise.

Every year Fonterra's farmers had to adjust their shares up and down, depending on what their production levels were, he said.

"This year the change in share standard allows us to have a buffer there so that if we have a slight increase in production, or a slight decrease, we don't then have to have an adjustment [in shares]."

McKenzie said farmers would be in a better position to buy more "dry shares" in May.

He said he was forced to "scale back" his own share purchase due to a dry period on his farm at the time he elected to buy shares.

"At that time I had to buy feed for my cows," he said.

McKenzie added that the majority of farmers were happy with the revenue gained by Fonterra through its share offer.

He said that if the share issue was put into a New Zealand sharemarket context, the amount raised would have been second only to the 2009 $450 million dual float of retailer Kathmandu on the NZX and ASX.

"$271 million is a sizeable amount," he said.

"As this is all part of the cooperative's evolution going forward, it's a very positive start and the shareholding will only grow as farmers increasingly get the financial means and confidence in Fonterra's performance to invest," said McKenzie.