Alyson Footer, Zachary Levine and Brian McTaggart have all just tweeted that Zach Duke and Jack Cust have been released. Both players have struggled this Spring, so it doesn't come as much of a surprise. I thought Duke, after his most recent outing, would of been given a shot at a bullpen spot, but it appears the Astros feel like they have better options for the bullpen. Zach Duke was signed to a minor-league contract at the end of January.
Jack Cust simply failed to hit, at one point being 0-24 this Spring. Cust was signed back in mid-January to a $600,000 deal with a club option for 2013.
It also appears that Minor League outfielder Jonathan Gaston has been released by the team, according to Gaston's twitter feed (h/t Subber10). Gaston was drafted in the seventh round of 2008. He's struggled to replicate his 2009 success in the Minors in which he hit for a .966 OPS in 607 plate appearances at high-A Lancaster.