As with all fish food, medicated feed should be stored in a cool, dry place. If available, a freezer is ideal for storing fish feed for extended periods. Antibiotics and essential nutrients will deteriorate rapidly in a warm, moist environment.
Excessive decomposition of antibiotics as a result of improper storage can result in unsuccessful treatment. Discard unused medicated feed after 4 months at room temperature.
Use of medicated feed in alternative species:
Antibiotics are approved for use only in catfish, salmonids, and lobsters. At this time, the FDA is considering approval of Terramycin® for striped bass and hybrid striped bass. Extensive tests demonstrating both the effectiveness and safety of each drug are required for each species of food fish and each disease to be treated.
These tests are very expensive and usually require years of experimental trials. Few drug companies can afford to spend the money needed for the approval process because of the small returns expected from the aquaculture industry as compared to traditional agriculture.
Universities, however, are participating in this essential testing process to aid the aquaculture industry. At the time of this writing, FDA will allow veterinarians to prescribe the use of medicated feed for fish species other than those listed on the label.
For example, Terramycin® medicated feed approved for use in catfish may be prescribed extra-labelly for hybrid striped bass by a licensed veterinarian. Check with a qualified fish health professional or veterinarian on the current status of medicated feed use regulations before treating your fish.
Summary:
Medicated feed is frequently recommended to control bacterial disease outbreaks. Medicated feed is a fish diet containing an antibiotic. Bacterial infections may be controlled by antibiotics. Only two antibiotics are available in medicated feeds for food fish.
Terramycin® contains the drug oxytetracycline. The FDA specifically approved Terramycin® for control of Aeromonas hydrophila and Pseudomonas sp. infections in catfish and Aeromonas salmonicida, A. salmonicida achromogens (Haemophilus piscium), A. hydrophila (A. liquefaciens), and Pseudomonas sp. in trout.
Terramycin® should be fed for at least 10 days, followed by a 21- day withdrawal period. It is only available in a sinking pellet. Romet® is a combination of two drugs, sulfadimethoxine and ormetoprim, that together are more effective than using either chemical alone.
It is approved by the FDA for treatment of Edwardsiella ictaluri infections in catfish and Aeromonas salmonicida infections in salmonids. Romet® should be fed for at least 5 days followed by a 3-day withdrawal period for catfish.
Trout, however, are required to have a 42-day withdrawal period from Romet® before being slaughtered. Because Romet® is available commercially in a floating pellet, this allows for pond observation of the fish eating the medicated feed.
If the fish have a bacterial disease and the causative agent has been identified, a sensitivity test should be performed by a fish health professional to ensure that the correct medication is used. A sensitivity test shows the resistance of the disease-causing bacteria to various antibiotics.
Regardless of the antibiotic feed used, treatments should always be the maximum recommended dose and should be fed for the total number of days recommended even if the fish appear to have recovered.
Feeding lower concentrations of antibiotics or decreasing the number of days the drug is fed can allow the bacterial pathogens to develop a resistance to the antibiotic. The antibiotic, then, would not be able to control certain infections that may occur later at your fish farm or hatchery.
Bacterial diseases are often a consequence of poor water quality, improper nutrition, excessive parasitism, or improper handling. These management problems must be corrected for successful, long-term control of infections.
Authors:
Robert M. Durborow and Ruth Francis-Floyd
