When referring to channel catfish production, the term medicated fish feed implies a prepared (commercial) feed which contains an antibiotic. Antibiotics are drugs specifically designed to control bacterial infections, but they do not control parasitic, viral, or fungal diseases.
There are many different types of antibiotics, but the Food and Drug Administration (FDA) has approved only two for use in catfish in the U.S.A. These are Terramycin and Romet. Each is discussed separately below.
1. Terramycin
Terramycin has been available for treatment of channel catfish for many years. It contains the drug Oxytetracycline . This drug is effective against many bacteria which cause disease of channel catfish, including all of those mentioned above. The FDA specifically approved it for
control of Aeromonas sp. and Pseudomonas sp. infections in channel catfish.
Terramycin is incorporated into catfish feed by commercial mills and fed at a rate of 2.5 to 3.75 grams of drug for 100 pounds of fish per day. To receive an adequate dosage, fish need to eat at least 2.5 percent of their body weight per day. Therefore, 100 channel catfishwhich weigh 1 pound each need to consume 2.5 pounds of Terramycin medicated feed to receive an adequatedosage.
Terramycin must be fed for 10 days, and the fish must be held an additional 21 days before they can be marketed to allow complete elimination of the drug from the fish. This 21-day withdrawal period assures that the drug will be absent from fish intended for human consumption.
Slaughter of fish before the end of the withdrawal period is a violation of federal law. Consider market plans before treating fish with Terramycin. Once treatment begins, the fish are non-saleable for 31 days (10-day treatment period + 21-day withdrawal period).
A final consideration when feeding Terramycin is that it is only available as a sinking feed. This drug is broken down by the high temperatures needed to make a pellet of fish feed “puff up” so it will float. Feeding a sinking fish food to sick fish is a disadvantage because it is very difficult to determine if fish have eaten the medicated food.
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2. Romet
Romet is a relatively new product approved by the FDA for use in channel catfish in 1985. This product is a potentiated sulfonamide which contains two drugs, sulfadimethoxine and ormetoprim. These two drugs work in combination and are more effective than either drug would be if used alone. Romet is also effective against many bacteria which can cause diseases of catfish. However, it is specifically approved for use against Edwardsiella ictaluri infections.
Generally, Romet is considered ineffective against F. columnaris. It is recommended that Romet not be used if catfish have a primary or secondary infection with F. columnaris. Romet is prepared by commercial feed mills and fed at a dosage of 22.7 mg drug per pound of fish (50 mg/kg) per day for 5 days.
The withdrawal period for Romet in channel catfish is only 3 days. This is considerably less than the withdrawal period for Terramycin. With only 5 days required for treatment and a 3-day withdrawal period, catfish treated with Romet can be slaughtered 9 days after the drug treatment is started.
Another advantage of Romet is its availability as a floating feed. This allows direct observation of the fish eating the medicated pellets. Again, early diagnosis and treatment are necessary because once fish are sick they are unlikely to eat.
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