Due to heavy rains & flooding, I've heard some areas may be closed right now to horse trail riding. I have not contacted these areas but please know from what I have heard, the possibility exists. You may want to reach out to any park which you are planning to visit and find out current conditions.
I was told that you cannot go beyond the cabooses at Two Rivers near Venice. This would mean you can't get to the horse camp or trail head, so assuming horse trail riding there is not available at this time. I was also told Halsey got 10.5" of rain in the last day or two and roads and trails in the Nebraska National Forest are closed. In addition, it was still raining at Indian Cave this morning and they don't anticipate the trails to dry out until this weekend, provided they get no more rain. So please, call before you haul to any of these locations.
And remember, riding on wet trails damages the our trails. Please let them dry before you ride.
See http://www.horsetrailriders.com/ for additional updates, if any.