apocalypsepony wrote:
If her weight is where you like it now, what I'd do is not change her hay, but cut her concentrated feed in half and see if she maintains her weight, loses weight or keeps gaining. Then adjust it up or down accordingly.
Yup. The more she can maintain on roughage the better.

Add in beet pulp and/or grass hay pellets instead of concentrate if she starts to lose a little condition and see if she can maintain on that.