Choke is a swallowing problem, not a breathing one
The name misleads people. In a horse, choke means a wad of feed has lodged in the oesophagus — the gullet that carries food from the mouth to the stomach — not in the windpipe. The airway stays open, so the horse can breathe, but nothing can get past the blockage in either direction: food and water cannot go down, and saliva, which a horse produces constantly, cannot be swallowed either. Everything backs up and overflows, which is what produces the alarming picture owners see. Most episodes involve greedily bolted feed — dry pellets, unsoaked fibrous feeds, chunks of apple or carrot, or a mouthful grabbed from a new round bale — and horses with sore mouths, missing teeth or a habit of eating against competition are repeat candidates. Some blockages soften and pass on their own; you cannot know in advance which kind you are watching.
The signs, as they unfold
Choke usually declares itself during or straight after a feed. The horse stops eating abruptly and looks anxious, stretching his neck out and down and making repeated, exaggerated swallowing movements that achieve nothing. Coughing and retching follow, and then the signature sign: a discharge of saliva mixed with chewed feed draining from both nostrils and sometimes drooling from the mouth. He may paw, sweat, shake his head or keep returning to the feed bucket and backing away from it. Owners sometimes report a horse who seems to be trying to be sick — horses cannot vomit, so what they are seeing is the retching effort against the blockage. Breathing is usually normal between coughing bouts; noisy, laboured breathing or a horse in real respiratory distress is a step beyond ordinary choke and should be described to the vet in those words.
What to do — and what never to do — while waiting
Remove everything edible. Take away feed, hay and water at once, because anything more he swallows can only add to what overflows towards the lungs, and keep him in a quiet stable where he cannot snatch at bedding. Keep him calm and still rather than walking him about, and let him stand with his head lowered if he chooses, since that helps discharge drain outwards. Then the list of don'ts, which matters more: do not syringe water into his mouth, do not pass a hose or tube down his throat, do not try to massage the blockage down the neck, and do not give any stored medicine in the hope of relaxing the gullet. All of those are vet work with the right equipment and sedation, and amateur versions risk pushing material into the airway. Phone the vet as soon as you recognise the picture, describe how long it has been going on and what he was eating, and keep watching him until they arrive.
After it clears: the second watch
When the blockage passes, the danger is not entirely over. Material that overflowed can be inhaled, and a chest infection may develop over the following days, so the vet will often want the horse checked again if he coughs persistently, goes off his feed, runs a dull feverish demeanour or breathes faster than normal. Note his temperature-taking cooperation, his appetite and his cough for a few days rather than assuming the crisis ended at the stable door. Keeping the owner, the yard help and the vet's updates in the one per-pet thread on his KinsLe Messenger hub means the person doing the evening check can see exactly what the vet said that morning, word for word.