Iron ore shipments for the quarter were 58 million tonnes, up 8% year-on-year, but down by 6% quarter-on-quarter.
UBS had forecast a strong rise in shipments to 68Mt, with BHP even missing RBC Capital Markets' more conservative estimate of 61Mt.
The company said the result was impacted by unplanned car dumper maintenance issues, with work now underway to improve availability.
Production for the nine months to March 31 rose by 2% to a record 175Mt, or 203Mt on a 100% basis.
Full-year guidance has been reduced to 236-238Mt, or 272-274Mt on a 100% basis, down from 239-243Mt and 275-280Mt respectively.
While copper output of 457,000 tonnes was largely in line with forecasts, the company reduced full-year guidance for Olympic Dam by 15,000t to 135,0...