Demoralised Nationals will meet on Monday morning to replace Barnaby Joyce.
Some Liberals have been unhappy at the prospect of Barnaby Joyce being acting prime minister when Malcolm Turnbull visits the US.
This is the second consecutive time the Nationals have chosen a female senator as deputy leader.
Two Nationals crossed the floor and four others failed to vote on a motion from Liberal Democrat David Leyonhjelm to disallow the import ban on the Adler lever-action shotgun.
The Turnbull government was caught out by not having any legislation for the Senate to consider.