Here is what the US Food and Drug Administration ("FDA") has to say about conditional approvals of veterinary vaccines:

Conditional Approval Explained: A Resource for Veterinarians, Food and Drug Administration

Thus, we see the effectiveness is unknown for the Zoetis bird flu vaccine. And equally concerning, the Zoetis vaccine does not meet the requirements noted in the two bullet points above for issuing a conditional license, because it would be relatively simple to demonstrate effectiveness with such a widespread infection. It would not require complex or difficult studies. All you would need is to vaccinate chickens with the vaccine and a placebo, then expose both groups to bird flu and see how many develop symptoms and how many succumb to the disease in each group.

Therefore, the vaccine is not legally eligible for a conditional approval.