Archangel
Normal, 10 cats ago
I've had a few horses reach significant ages now.she's out 24/7, she's only have 1 feed a day as with collage I physically can not get up more. They get hay in field and when I bring her in she has a net of hay
They were all different in how they aged, but the thing they all had in common was that they needed more fibre - nothing fancy - just lots of easy to chew soaked fibre.
I think your horse needs similar and ideally that will need 2 feeds a day.
As an example, my latest horse to get old is now 32, he can eat grass and hay fine, but his teeth now have grooves in them so he doesn't get the full benefit from his food.
In the winter he gets 4kg supplementary soaked fibre (Spillers Senior Supermash/Bailey Meadow Cobs) a day - in 2 feeds.
He looks fabulous, but without the above, he would come out of winter like a hat rack.