If your horse is otherwise normal, it is not unusual for a horse to lie down in the pasture if the weather is good and he is very comfortable with his surroundings.
As for the Wisolan, I'm not familiar with this herbal product and could not find any scientific data on the product. The only information that was available was anecdotal evidence on the ability of this product to help in respiratory conditions. If the condition persists or if your horse has a worsening of his clinical signs, I would recommend that you have him examined by an equine veterinarian.
