A horse that is refusing to eat and drink would require a visit from your vet. Horses generally have a voracious appetite and a refusal to eat signifies a medical problem. While some problems like excess gas may be temporary, there are several more serious conditions like infectious diseases that could account for such behavior. Before you call your vet, you can make sure of your horse’s temperature and pulse. Under normal circumstances, a horse’s temperature would be 38°C and his pulse would be anywhere between 30 to 40 beats per minute. You can also check your horses rate of respiration which would normally be about 10-15 breaths per minute. Make sure that you use a thermometer that is meant specifically for animals as these are sturdier than those meant for humans. To check your horse’s pulse rate you can place you finger just below the angle of the jaw and press down very slightly. It may take a while to find the correct spot but make sure that you do not use excessive pressure. When your finger is on the right spot you will be able to feel a very distinct pulse. In order to take his respiration rate, you can watch the rise and fall of his flanks.
You mentioned that your horse is not rolling about and does not seem colicky. While rolling about is one of the most common symptoms of colic in horse, it may not always occur. Colic is an intestinal problem and so if your horse is showing any other signs of abdominal distress, such as biting his belly or kicking out repeatedly, it is possible that he has colic. A horse with colic will also have an elevated respiration rate as well as a higher pulse rate.
If your horse is able to walk, you can take him for a very short walk. This will help to detect any lameness in horse that could be the cause of his behavior. There are several other neurological problems and illnesses that can result in these symptoms. Influenza is one such possibility but it would generally include either a dry cough or increased mucus secretion. Influenza in horses is quite common and generally disappears within a week or so. Since your horse seems to want to be off his feet as much as possible, it is possible that he has a hoof infection or disease. Laminitis is one such disease which causes a horse to remain off its feet and the discomfort can cause it to refuse food and water.
For proper horse health, it is essential to get your vet’s opinion before proceeding with any kind of treatment as incorrect medication can aggravate the condition.