Purina Pet Advisors are available to answer general questions at 1-800-778-7462 (1-800-7PURINA)
(Mon. - Fri., 7 a.m. - 7 p.m. CT).
They also have a web based email form located at:
firstname.lastname@example.org - registered email address for the Purina domain on Admin contacts. I'd start with the web based form and if you do not receive a response, you can contact them via this email address. Best results might actually be to call them during business hours on their help line.