Is it safe to get a tattoo behind your ear?
What is the best treatment for an abscess on a horse?
What is the proper pin placement for bowling?
What is the standard bowling pin weight?
Why are horses' tongues tied back during races?
Why do people say "PIN number"?
Why would I need a Visa pin number?
Most likely the saddle is pinching him somewhere, probably at the shoulder. If it isn't the saddle, it still definitely means he is feeling pain/discomfort somewhere.
He is angry or uncomfortable. Maybe lounging him or talking to him or he needs to be trained how to trot.
Your horse is protecting himself from either fear, or pain, he is telling you something is wrong. Be sure your tack fits properly Is there a medical condition needing attention?
This is how your horse indicates that he's annoyed, angry and wants to assert himself rather than do what you want him to do.
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