The Shenzhen stock exchange-listed shares dropped 10% to 11.87 Chinese yuan, the lowest level since Fonterra paid 18 yuan a share for an 18.8% stake in the firm.
Beingmate's shares had recovered after more than halving in value in July but tumbled 19% in the latest Chinese equity sell-off.
China's share markets have been hit the hardest over the past three days after a gauge of manufacturing hinted at a slowing economy in the world's most populous nation, spooking investors across the globe.
The Shanghai Composite was down 4.1% in early trading, following an 8.5% slump yesterday.
In March, Fonterra paid 3.46 billion yuan or $756m for the stake. That dropped to 2.28 billion yuan at today's price and $546.5m at the current cross-rate.
Fonterra and Beingmate announced their global partnership last August to help meet China’s growing demand for infant formula and increase export volumes of Fonterra’s Anmum infant formula brand.
At the time, the world's largest dairy exporter had sought as much as 20% of the company and flagged it would cost about $615m.
The New Zealand dairy exporter raised 1b yuan through a dim sum bond in June to help pay for the Beingmate acquisition.
Tumbling global dairy prices prompted ratings agency Standard and Poor's this month to put Fonterra's A long-term and A-1 short-term ratings on CreditWatch negative, saying "high debt levels reflecting the sizable acquisition of a shareholding in China-based Beingmate combined with peak capital expenditure at this low point in the dairy price cycle will place Fonterra's key credit metrics under pressure in the short term."
Fonterra slashed the amount of milk powder it was selling through the GlobalDairyTrade online auction in a bid to prop up international dairy prices that had been in a slump this year.
The dairy exporter slashed its forecast payout to farmers for this season and was looking at ways to drive a more efficient operation, hiring management consultancy McKinsey and Co to advise on the review which had already seen 523 jobs go.
Units in the Fonterra Shareholders' Fund, which give investors access to Fonterra's dividends, fell 0.6% to $4.82. – BusinessDesk
