My friend moved her horse to the barn i'm at about a month or so ago; he'd just come from training and when he arrived he was ill. He had a snotty nose and a cough. The vet was out multiple times and he had 3 rounds of antibiotics, I still have no idea what this horse was ill with.
Jump to today, my horse has a snotty nose and has coughed, he also seemed to cough up some white goo. His snot is white and possibly a little yellow. The barn manager is going to keep an eye on him but I wanted opinions of what it could be. Generally he looks fine, is eating and drinking, is stubborn as ever. I wouldn't have noticed he might be ill if I hadn't seen the snot and watched him cough. His cough sounds dry.