Prices of dairy products fell by the most in eight months on Fonterra's GlobalDairyTrade platform amid concern demand for commodities may be slowing with China's growth outlook.

The GDT-TWI Price Index fell 4.5 per cent compared to the last sale two weeks ago. The average winning price declined to US$3,396 a metric tonne, the lowest since August 2010.

See the full results here.

The sale is the first on GlobalDairyTrade since Fonterra cut its 2011/12 forecast payout this month, citing the high New Zealand dollar, falling commodity prices and increased production from Northern Hemisphere rivals. The Thomson Reuters/Jefferies CRB Commodity Index fell 1.3 per cent overnight.

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The average winning price for while milk powder fell 2.6 per cent to US$3,316 a metric tonne and skim milk powder fell 2 per cent to US$3,125 a tonne.

Anhydrous milk fat dropped 9.5 per cent to US$3,284 a tonne. Butter milk powder wasn't offered at this week's sale.

Cheddar fell 11.3 per cent to US$3,114 a tonne and milk protein concentrate declined 15 per cent to US4,345 a tonne. Rennet casein fell 12.9 per cent to US$6,545 a tonne.

There were 123 winning bidders over 10 rounds, out of 145 participating bidders. The number of qualified bidders rose to 592 from 580.