Best feed for more stamina without heating?

[Stenners]

My girl is worked 4-5 days a week and was hacking or schooling and been fine but her workload has now increased (since xmas) and I'm finding she tires quite quickly (she's quite fit) so I'm looking for something with to give her more energy/stamina without heating her up or putting on too much weight as she's an ideal weight at the moment.

She's currently fed Hifi, spillers daily balancer and linseed. I've also just bought topspec cool condition cubes which i've just started in the last few days but not at the full amount.

I've had horses before that go crazy on some feeds so it always worries me!

 

[Pearlsacarolsinger]

Doesn't HiFi contain chopped straw? I would swap it for something slightly more calorific, maybe dried grass chaff, or if she's ok with alfalfa, Alfa A oil. But she doesn't sound fit enough for the work, so you will need to work on that too, when she has the resources to increase her work.