Horses can choke on chunks of vegetables like carrot or sweet potato.
To be clear - when horses suffer choke - it does not mean the food goes down the wrong pipe. It means the food is lodged in the oesophagus and will not shift. This can press on the windpipe if severe enough, but usually what will happen if the horse cannot resolve the choke, the horse will be unable to eat or drink and will die of dehydration. Saliva may also slip into the trachea and cause pneumonia.
How should vegetables and fruit be cut up in a way to minimise the risk of choking in horses?
Related: What treats are safe for horses?