I have been trying for several days to get my horse to go into the nether. I am playing survival vanilla Minecraft 1.14.4. At first, I thought maybe it wasn't possible to get a horse into the nether. But I did some research and found that as long as you are not riding the horse, it will go through the portal. This is a quote from the Official Minecraft Wiki on Horses:

"It is impossible for a player to use a Nether portal while on a horse. It is possible however, to enter the portal on the horse and then dismount, sending the horse through the portal on its own, or use a lead to position the horse, then push it through the portal."

I tried both pushing the horse through the portal and dismounting from the horse in the portal multiple times but nothing seemed to work. I restarted the game and my computer and it still wouldn't work.

**I am able to go through the portal.

Here are some videos of the bug:

This first one shows me dismounting from the horse in the nether portal:

Horse Short.mov

This second video shows me pushing the horse into the nether portal:

Horse Short 2.mov

These both clearly didn't work. I tried both ways at least 10 times.