Prices for skim milk powder (SMP) and whole milk powder (WMP) saw the biggest decreases at Tuesday's GDT.
Prices for SMP fell 15.5% to $2,118/t while New Zealand's most important product WMP saw prices slip by 12.4% to $2,782/t.
Butter prices were up 1.2% to $4,653/t, while cheddar saw a drop of 4.2% to $3,435/t.
Overall, prices were back 6.3% to $3,512/t.
This is the second consecutive fall in the GDT. Prices at the auction two weeks ago slipped by 3.2%.
Prices at the latest GDT auction.
Price fall not justified
IFA dairy committee chair Seán O'Leary said the GDT does not hold the significance it once did for Irish dairy farmers.
O'Leary said the "GDT traded only 636,000t of product during 2016 - down 36% on the peak levels of trade of 2014, and consisting mostly of WMP and SMP".
"While it is an important international price discovery mechanism, and clearly influences buyers and sellers, it accounts for a small and decreasing portion of actual global trade, and is less important to us than EU exports and trade. It is, therefore, essential that co-ops would at all times put GDT in proper perspective, including this month when deciding on February milk price," O'Leary said.