A novel delivery of oxytetracycline in turkey breeder hens

A novel. product (SQ12) for subcutaneous (SQ) injectable delivery of oxytet racycline (OTC) has been developed for use in livestock. SQ12 employs micro fluidic spheres encasing OTC crystals, which allows for longer release of t he OTC compared with other injectable antibiotics. The objectives of the st udy were to determine serum and tissue levels of SQ12 in turkey breeder hen s to 14 days postinjection and to evaluate effects of SQ12 on reproductive status. Thirty photostimulated hens were housed in litter floor pens and pr ovided with 14.5 hr of light per day in a curtain-sided facility. Six hens served as untreated controls. Twelve hens per treatment group received SQ i njections in the neck with SQ12 at 11.4 (L dose group) or 22.7 mg/kg (H dos e group) to assess low and high doses, respectively. Serum samples were obt ained from each hen at predose and 6, 12, 24, 48, 72, 96, 168, 240, and 336 hr post-injection. All hens were euthanatized at 14 and 15 days postinject ion. One-half of the hens in each treatment group were sampled (liver, lung , kidneys, and breast muscle) for tissue residue levels of OTC. The control group had no detectable OTC in serum or tissues at: any sample collection time. There were no detectable serum levels of OTC in either treatment grou p prior to injection. The average serum concentrations of the L and H dose groups showed similar depletion curves although the H dose group was 42% hi gher at maximum concentration than the L group. Average tissue concentratio n of OTC for all tissues sampled from the H dose group was twice that of th e L dose group. All tissue levels were below the OTC residue tolerance limi t. SQ12 provided an extended source of OTC in serum of turkey breeder hens with no effect on reproductive status. SQ12 may provide for a novel treatme nt of bacterial infection in turkey breeder hens with longer lasting serum levels compared with other single injectable OTC products.