And this is why I write software for a living. Because "Take the chicken to pieces to find out why it's broken" makes sense to me, so I'd be a rubbish chicken doctor.
From what I understand, that actually is common for chickens because they're usually livestock rather than pets. If one chicken might be sick, you care more about whether it's contagious than the outcome to the one chicken, so you do the most thorough diagnostics you can even if that requires an autopsy.
I like working with vets for my stuff (epidemiology) because there are really interesting constraints.
As you mention, one chicken is expendable, but you're worried about tens of thousands of birds.
A sheep is...mostly expendable. You have a low, market driven cap on what you can spend.
A dog or cat, less so - there's an emotional connection, but there's also an upper threshold (with a wide range, and who has what threshold is often surprising).
A race horse...well, let's just say equine ICUs are really pretty nice, all things considered.
