Possible Clues:

• Had trouble swallowing
• Was joker unable to speak?
• By Gad, sir, that's about to be laid up without a word
• There's an egg up in there, by Gad!
• Like a hostage, perhaps
• Choked, so unable to speak
• Made jokes when bound not to speak
• Nothing can be said for a horse in such an aged way
• Muffled or retched
• You'll get nothing straight from the horse's mouth if the horse is in so aged a way like this