* What horse are you talking about? Is it a specific horse, or are you talking about horses in general?
* What is its appearance like? Is it healthy, thin, injured? What breed is it? What is its coat colour and markings?
* What is its behaviour like? Is it calm, agitated, playful, aggressive?
Once I have this information, I can give you a more specific and helpful answer.
For example, if you tell me about a horse that is thin and has dull coat, I can tell you that this could be a sign of poor nutrition or illness. Or, if you tell me about a horse that is pawing the ground and sweating, I can tell you that this could be a sign of anxiety or pain.