Keelan said that daytime has gone through a "pretty significant shift" in recent years and so it was "interesting" to read the Trust's calls for improvement.
On Monday, the BBC's governing body called on the corporation to move away from daytime programmes that viewers perceive to "lack quality and originality". Particular criticism was levelled at the amount of property and collectibles shows in the schedule.
The Trust said that the overall ambition of daytime on BBC One and BBC Two is not meeting audience expectations, and BBC management must now explore options for improving the quality and distinctiveness of output within current funding levels.
Writing on the BBC TV Blog, Keelan said that the decision to stop airing long-running Australian soap Neighbours in February 2008 felt like a "major loss to the schedule".
However, he said that the move worked to free up space and, more importantly, money to invest in the daytime schedule to make it feel "much more distinctive than our rivals".
Keelan said that BBC Daytime has since increased its amount of current and consumer affairs programmes by 140% - a rise from around 80 hours to nearly 200 hours projected for 2010 - including new shows Rip Off Britain and The Estate We're In.
He said that the BBC has also focused on bringing on more UK-originated drama, including additional episodes of the long-running Doctors.
Daytime has further commissioned more "event" dramas, such as the Pauline Quirke-starring Missing, along with Land Girls and Moving On.
Keelan highlighted that certain property programmes have been decommissioned, such as The Unsellables, while daytime factual shows Fake Britain, Real Rescues and Dom's On The Case: NHS, have recently been promoted to primetime.
"The Trust rightly gives us credit for the range of programmes in daytime: we launched more than 50 different shows last year compared with fewer than 10 on each of our commercial rivals," said Keelan.
"A large influx of new programmes, such as those mentioned above, does of course mean we have to lose others from the schedule to make space. Most recently Car Booty has been decommissioned alongside property series such as The Unsellables.
"The Trust has also acknowledged that daytime has already started the process of changing its mix of programmes - the challenge remains to continue to provide the broadest range of programming of any broadcaster.
"Despite challenging budgets - a daytime series budget is roughly a quarter of a peaktime series - the aim in daytime will always be to produce the highest quality programming other broadcasters wouldn't go near."
In the autumn, daytime will air Sanjeev Bhaskar's new drama The Indian Doctor. It will also soon start broadcasting the next series of Moving On.
Brookside writer Jimmy McGovern, who is executive producer on Moving On, said: "This series just wouldn't have been possible without BBC Daytime's commitment to commissioning drama that takes risks.
"Drama with something to say. Drama that is inexpensive. Drama that is excellent value for money."