"Anhydrous milk fat has been undervalued relative to butter on a milk fat content basis for quite some time," Castleton noted. The latest results "go quite some way to closing the gap, but AMF is still undervalued relative to butter."
Skim milk powder gained 3 per cent to US$2,047 a tonne, while butter rose 2.4 per cent to US$5,787 a tonne.
Bucking the trend, lactose dropped 3.5 per cent to US$687 a tonne, while rennet casein shed 6.1 per cent to US$4,876 a tonne.
Butter milk powder was not offered at this event.
For sweet whey powder, neither an index nor a price was available.
The New Zealand dollar was trading at US68.66c as of 2.31pm in New York, compared with US69.13c at the previous close.
There were 111 winning bidders out of 164 participating at the 14-round auction. The number of registered bidders rose to 527, up from 519 at the previous auction.