Uptake and elimination of florfenicol in Atlantic cod (Gadus morhua) larvae delivered orally through bioencapsulation in the brine shrimp Artemia franciscana

As an approach to combat bacterial infections, incorporation of florfenicol in Atlantic cod (Gadus morhua) larvae, administered orally through bioencapsulation in Artemia franciscana nauplii, was investigated. Artemia nauplii were enriched with 1000 mg/l florfenicol for 30 min and administered as a single dose, or daily for three consecutive days. The concentration of florfenicol in the medicated nauplii, and in the cod larvae, was analysed by high performance liquid chromatography (HPLC). Following a single oral administration, the elimination half-life (t½β) was calculated to 14 h, Cmax to 4.7 μg/g dry weight (14.3 ng/larva), Tmax to 0.5 h, and MRT to 20 h, respectively. An hour after administration of batch 1 in the triple dose study, a mean florfenicol concentration of 4.6 μg/g dry weight (14.0 ng/larva) was found in the cod larvae. One hour following administration of batch 2 and 3, corresponding values were 5.9 μg/g dry weight (17.9 ng/larva) and 4.2 μg/g dry weight (12.8 ng/larva), respectively. These data show that medication of cod larvae using Artemia nauplii as carriers of florfenicol is a promising approach for treatment.