Aquaponics: there are catfish in this tank, fe...

Aquaponic Systems: there are fish in the tank below that are feeding the plants above. (Photo credit: Wikipedia)

In animal biology, there are a number of terms and phrases that are thrown around wildly. For the average individual though, some of these are never really clearly explained or defined. In our Aquaponics classes, we have found that one of the most confusing is the importance of a Feed Conversion Rate for efficient animal production.

The simplest explanation is that a food-conversion rate is really a ratio that helps to determine the efficiency at which an animal converts food into body mass.


For the farmer, this translates to help in making the decision of which species to raise. This ratio can help the farmer to determine which crop is really the best for your goals, by showing clearly how much feed is needed to produce a specific weight at harvest. The ratio is commonly presented as the amount of feed provided in relation to the amount of weight gain on the animal.


English: Cow and calf

English: Cow and calf (Photo credit: Wikipedia)

To help understand why fish are considered to be exceptional, it is important to the discussion with common terrestrial species like Cattle and Swine. These common farm animals have a FCRs that ranges roughly between 4-8 pounds of feed per pound of harvested body weight (4-8:1). This means that in general terms, you would feed between 4 – 8 pounds of feed for every pound of body mass. For animals raised using heavily viagra lawsuits won in court in 2010 commercialized diets using large amount of highly processed ingredients, the FCR is generally on the high end. For the purposes of our general calculation, that means that if you wanted to raise a 50 pound beef calf to a harvest weight of 550 pounds, you would need to provide a minimum of 2,000 pounds of feed (and up to 4,000) for that one animal alone. Now this doesn’t even take into account that this is a 1-2 year process.


Channel catfish

Channel catfish (Photo credit: Matt Tillett)

With fish the rate of feed conversion (FCR) is significantly greater. Many species of fish have been found to have ratios that range from 1.5-4 pounds feed per pound of harvested body weight (1.5-4:1). While many fish are on the higher end of that range (which is still generally better than most Terrestrial animals), there are actually a large number of currently cultured fish species that have feed efficiencies in the middle or lower end of that range. Data gathered by many commercial Channel Catfish (Ictalurus punctatus) farmers in Mississippi, show that they routinely produce millions of pounds of harvestable catfish with a FCR of 2:1. Data for commercial harvest of the various Tilapia species is amorphous, but reputable sources have reported that they have reliably raised crops with an FCR as low as 1.5:1 (though admittedly the feed efficiency for Tilapia is usually around 2.5:1.)

(Content derived in part from an Aquaculture curriculum developed by The Council for Agricultural Education, Alexandria, Virginia 1992.)


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