My horse keeps digging everywhere!

[Huy]

I wonder if there is a trait to restrain him/her beside turn of the free will 'cause carrots, onions and potatoes are everywhere on the ground!

[MoMoll]

Training. Scold the horse for being "piggy"

[Huy]

i'll take that in mind ! at first my horse had a piggy trait! I removed it and it still dig!

[Rainbow Dash]

There's always the option of fencing the garden in, putting up a gate and locking it to pets.  Have you tried that yet? That's how I keep Deers and Wild Horses out of my garden, by locking the gate to everyone but my Gardener Sim. 

[Ricalynn]

I don't think there is really anything you can do to make them stop digging in your yard except keep their action queue full.   Horses seem to do it randomly.  Maybe get a horse ball.

[Pam]

Fences with gates work great for keeping all animals out.  I never have a garden without a gated fence anymore.

[Ricalynn]

I don't think Huy is talking about the garden being a problem.  I'm fairly certain they are referring to action horses take when they dig in the ground with their hoof.  Some of the times when it's done, a vegetable will appear that can be eaten by the horse. 

[MoMoll]

i'll take that in mind ! at first my horse had a piggy trait! I removed it and it still dig!

Even though you changed the trait, he's still piggy.

[Huy]

Building & locking fence seem to work awesome!