And what advice would that be? On a bike your in total control which is not the case on a horse. I don't see how a horse can put a cyclist in danger by approaching them unawares.
I'm not aware of what advise could be given to a horse rider if any, although I expect someone who rides both bikes and horses would have a better understanding that myself.
If you are not in control of a horse imho you should question if you should have it in public as its a powerful animal which you need to be in control of for your safety, the safety of others and the safety of the horse.
Understanding the challenges other road users have to ensure that we share the road in a safe manner, based on the information I have gained in threads such as this I slow down to ensure that I am not threatening to the animal give it lots of space and announce my presence vocally.
I and some friends came across a horse being ridden at quite a pace through some remote trails which we ride my MTB on. The pace suggested that the owner did not expect to come across anyone and when she did, the horse reacted in what I perceive as being extreme fear/shock having never seen any other horses react in this manner. The result was that one of my friends and the horse rider ended up on the floor looking less than comfortable...
In the same manner that threads likes this educated me, Im sure that many horse riders are not aware of the challenges facing cyclists in different environments which is why I asked the question