Target Animal Safety of Litopenaeus Vannamei Treated with Oxytetracycline in Feed

<p>Project Summary/Abstract: Oxytetracycline has been effectively used in reducing the mortality of cultured shrimp infected with necrotizing hepatopancreatitis. Under the auspices of an INADA, data has been gathered on the effectiveness, human food safety, target animal safety, and environmental safety. A Target Animal Safety study was conducted in 2004 with treatment levels of 4.5 (1X), 13.5 (3X) and 22.5 (5X) g OTC per kg of feed. This study showed anomalous toxicity at the 13.5 g OTC/kg level (3X), with no toxicity demonstrated in the control, 1X or 5X treatments. Thus, a margin of safety could not be determined. The present study is a repeat of the first with treatment levels of 1X, 1.5X, and 2X OTC in feed with a control group. A randomized block design will be used with8 blocks of 4 tanks each. Each tank will contain 12-15 animals depending on the size at inception. The treatments will receive medicated feed (or a control diet) at levels based on preliminary consumption trials with age mates in similar tanks. The medicated treatments will be fed medicated diet for three 14 day periods. Each period will be broken by a 5 day period on un medicated diet. Random shrimp will be fixed for histological examination at the end of the first medicated period, the second period, the beginning of the third, the end of the third, and 14 days post medicated termination. The fixed samples will be examined for lesions in the hepatopancreas and graded as to severity of lesions seen. In addition, data will be maintained on the water quality, number of moribund and dead animals, consumption, and estimations of activity and appetite throughout the study. Growth will be estimated by determining the average weight per shrimp in each tank at the beginning and at termination of the study. The study will be conducted on the Good Laboratory Practice principles in 21 CFR 58. Final body weight by group, mortality, and feed consumption will be analyzed statistically for between group differences. Histological results will provide graded levels of lipid vacuolization, and lesion present in the hepatopancreas. These graded results will be analyzed using contingency tables. These data should provide information allowing CVM to establish a margin of safety within the treatment levels of the study.</p>