Higher bioavailability of doxycycline in broiler chickens with a novel in-feed pharmaceutical formulation

Bioavailability of a new, long-acting (LA) pharmaceutical preparation for administering doxycycline as in-feed medication to broiler chickens was compared to the standard in-feed administration of doxycycline. A commercial poultry house harboring Ross-308 broiler chickens, weighing 450 g, was divided into 7 sections as follows: doxy-FOLA group (n = 6,000 chickens divided into 3 replicates) medicated with 10% doxycyline, long-acting pellets at a dose of 400 g of doxycycline HCl/ton of food, resulting in a calculated dose of 48 mg/kg for 5 d; doxy-ref group (n = 6,000, divided into 3 replicates) medicated as for doxy-FOLA, but using a 20% commercial preparation of doxycycline. A third group of 300 broiler chickens (divided into 3 replicates), received a single IV dose of 48 mg/kg from a 2.4% solution of doxycycline HCl under ketamine anesthesia. Blood samples were obtained at designated times, serum was harvested, and doxycycline concentrations determined by high-performance liquid chromatography (HPLC). Bioavailability values were 156% and 227% on d 1 and 5 for doxy-FOLA and 13% and 23% for doxy-ref, on the same days. Mean residence time (MRT) and elimination half-life (T½β) were statistically different (P