If this veterinarian isn't interested in treating chickens, that's fair. Better to be up front about it. rather than muddling through without caring about how to do things!
Call around and find someone who might be interested! Ideally, there's a veterinarian who has chickens, or a staff member with chickens, and is interested.
Nobody can learn everything about every species!!!
Having enough clients who have poultry, and who are willing to SPEND MONEY on them, is a big part of the problem, unless the individual vet has a personal interest in that species.
Mary