poultry vitamin supplement expiration?

[galaxyflyer1]

Hello,

I use gp poultry supplement in the drinking water. I was wondering if anyone out there would know what the shelf life would be of this supplement. (Probably the same as any other) I have had my bottle for over a year now and I keep it in the shaded coop but it does get warm in there. Hopefully I'm not poisoning my birds now.

BTW, the bottle has no expiration date nor temperature storing recommendations.

Thanks,
Bob