I’m going to go against the grain here and before I start I will mention that I used to be a keen horse rider, from about 5 to late teens.
Most dogs have never seen a horse, they are not an easy thing therefore to train a dog to ignore.
Most yard owners would be not allow you to take a dog in to do some training and depending on where you live seeing a horse out and about may be a rarity.
it is common knowledge that dogs will attack sheep and fields that contain sheep are usually signposted and obvious so they are generally, luckily, very easy to avoid or walk through with the leash clipped on and short.
Dogs will often chase and harass horses much like sheep but unlike sheep they can pop up where you don’t expect them and because most dogs have never seen one they are a new and novel thing that the dog won’t have been trained to ignore.
I’ve come across horses three times with with my dog, the first time she was leashed at a fete and unbeknownst to me there was a horse there for pony rides and the owner was exercising it, my dog ran and spun with such force at the sight of the horse cantering its a miracle she didn’t injure herself.
The second time she was, thank god, on lead.
Usually, it’s a place where I have her off the lead.
The horse was in a spot where I walk at least 3 days a week and have done for the past 6 years or so.
You would never in a million years expect a horse to be there and I dread to think what would have happened had she been loose.
The third time I saw two in the distance, different area, i had time to quickly leash her before she spotted them.
Again, an area I very regularly walk, never seen a horse there and wouldn’t expect to.
It’s a very popular dog walking spot, it’s especially popular for off leash exercise.
This is common knowledge.
To ride a horse in a known, extremely popular dog walking area where you know large amounts of dogs will be off leash is irresponsible and stupid.
Dogs are predatory animals, they will chase animals like sheep and horses.
If I know there are sheep and horses in an area I will avoid or opt to leash her.
It really angers me when horse owners think they are entitled to ride in places where you wouldn’t expect them to be, places where you expect loose dogs to be.