The share offer was oversubscribed and will add an extra 58.8 million shares to the dairy company's register, priced at NZ68¢ each.

The company's shares jumped as high as 13.9 per cent to 74¢ on the ASX on Friday before closing up 10 per cent at 71.5¢.

A2 chief executive Geoff Babidge said sales of its Platinum infant formula brand were higher than expected and on track to triple from last year.

Such was the growth, Mr Babidge said the company was struggling to meet demand. He often heard from supermarkets, "the product's on the shelf for five minutes and then it's gone".

"Infant formula is emerging as a more significant and meaningful growth driver for the company than expected, with a current focus on sales in Australia and New Zealand and in China," he said.

Yet the company's biggest shareholder, the Perich family-backed Freedom Foods, did not participate in the capital raising. A company spokeswoman said on Thursday Freedom Foods chief executive Rory Macleod had been blindsided by the offer.

As a result, Freedom's 19.2 per cent stake in a2 will shrink to 17.6 per cent. Freedom's shares were almost 1 per cent lower on Friday at $3.02. The broader market, meanwhile, closed up 1.3 per cent.

A2 had agreed to halt its capital raising plans after Freedom and US dairy giant Dean Foods lobbed a conditional takeover bid in June.

But the bid evaporated after the US regulator launched an insider trading investigation into Dean.

A2 engaged Goldman Sachs to complete the share sale offer, which it targeted at fund managers.

Mr Babidge said the capital raising was "an important step in strengthening the company's balance sheet, and will provide flexibility to execute on opportunities consistent with our growth strategy".

The new shares will begin trading on the NZ Stock Exchange and ASX on October 15.