breathing during race

Question
I have a 3yr old filly with some potential. She raced yesterday in a 1300mtr race.She jumped very quick and lead but as soon as she was pushed to rail (as she was in barrier 13) she held her breath under pressure.
She trialled couple weeks ago where she jumped to the front and won by 2 1/2 lenghths, although she held breath again in the last 300mtrs when asked to quicken.

What can we do to stop her from continuing to hold her breath when under pressure?

Answer
thank you for the question. does she run with a tongue tie??  sometime that will help her breath much better. if she is holding her breath, then that is a problem that she is in control of . i would work her and tie her tongue and see if that helps any. work outs  will let you see when and why she holds her breath. other then that, if you are not absolutely sure she is hold her breath, you might have your vet scope her to make sure she does not have some other problem with her breathing as a flap problem etc. hope this helps you  thanks ED HESS