Instead of reading lips, try reading the ears of a horse. The ears of a horse can express a lot of what the equine is trying to say. When the horse's ears are pinned back and he is showing you the whites of his eyes, watch out, he means business! There are milder versions of this expressions as his ears might be pulled back just because he's annoyed or maybe he's even listening to noises behind him. However, when the eyes are bugged out with ears pinned back flat, beware.
The ears of a horse can show signs of aggression as mentioned above or signs of boredom. When the ears of a horse are turned back and jutting out gently, it is usually a sign of ennui. Make sure that the horse is aware of your presence before your approach as not to
risk startling him.
The positions of ears to the back and to the side have been discussed. All that remains are ears in the forward position. At this position, it usually means that the horse is alert. Occasionally, he might turn his ears back when you're riding him as to listen to
your commands. Conversely, a horse might be ultra alert because he senses danger. Ears pricked forward and stiff along with tense muscles can signal fear. Being prey animals, horses can pick up a lot of things to get twitchy about. If the horse does is constantly on high alert, gentle corrective measures should take place.
There are many nuances when reading a horse's body language and its ears are just one aspect of learning the way horses communicate. However, it is his most expressive body part.
In horse racing, there is a famous expression, straight from the horse's mouth to indicate who is the likely winner. This information jokingly comes from those in the trusted inner circle - being the horse himself. But from what we know of horse communication, perhaps it would be more accurate to change it straight from the horse's ears? Perhaps, but it doesn't have the same ring and the show Mr. Ed would not have been nearly as funny.