[kitten_Val]

Before you call the vet... Is it the same food and SAME bag? I had similar problem with my horses 3 weeks ago: opened new bag of Triple Crown (I've been feeding same feed for couple month) and they REFUSED to eat it. Jemma somewhat ate, but Kiara behaved same way as your horse. Obviously something was wrong with the feed in bag. I switched them to another one and they were just fine.

 

[kitten_Val]

Well, my horse Dozer is eating it fine, so is the donkey Radar, I opened this a day or two ago and he ate it then.

I'd get the vet then (at least call and describe what's going on and get the opinion). There is a possibility he could of bite on a bug and burn the mouth or throat. Or anything else. In any case, it's better to be safe then sorry.