I made a stable as shown in the picture and put all the horses tied up with the fence by the lashes. But it seems that all the lashes got to be found on the ground when I just load the save world. They are not with the horses and the fences. This happens same with the cats, dogs, snow golems and iron golems too. All lashes are on the ground from the whole saved world. Looks like there is a bug with the lashes (not the horses). Due to it, I lost two horses and an iron golem.