The effective usage of minocycline to treat specific bacterial and rickettsial infections depends on its degree of bioavailabilty.
Researchers at the University of Illinois’ College of Veterinary Medicine looked into the effects of fasting versus feeding on minocycline pharmacokinetics [Echeverria, K.O.; Lascola, K.M.; Giguere, S.; and Foreman, J.H. Effect of feeding on the pharmacokinetics of oral minocycline in healthy adult horses. The Veterinary Journal, Sept 11 2017].
The study concluded that fasting overnight and a delay in feeding hay for two hours following oral medication administration results in greater bioavailability of minocycline.