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Finding Fish Feed Formulas for Sunshine Bass

Wednesday, June 16, 2004

More than 40 percent of the variable cost of Sunshine Bass " or hybrid striped bass Morone chrysops x M. saxatilis farming is attributed to feed. One strategy to reduce costs is to find other, less expensive ingredients to use in commercial diets. U.S. Department of Agriculture-ARS physiologist Steven Rawles is studying nutrition in adult hybrid bass. He's interested in the digestibility and metabolism of nutrients and energy from commercially available feed ingredients and blended components for extruded hybrid striped bass diets.

Sunshine bass require protein-rich diets that are high in fats but low in carbohydrates. Ingredients in commercially formulated diets vary from company to company.

"Grains such as rice, corn, oats, and barley might be substituted for wheat and wheat middlings," Rawles says. "We're evaluating the production performance of fish fed these alternative carbohydrates to see whether they perform as well as fish fed diets that contain wheat or wheat middlings."

Rawles collaborated with  Aquafeed.com Expert, Delbert M. Gatlin, III, a professor at Texas A&M University's Department of Wildlife and Fisheries Sciences, to determine nutrient availability in 19 common feedstuffs for hybrid striped bass and red drum. They used commercial methods and equipment to manufacture extruded feed, in which ingredients are combined under high temperature, pressure, and shear force and ejected as bite-sized pellets. Nutrient digestibility values were determined and made available to feed mills and producers. This research could lead to lower-cost feeds.

Rawles and colleagues are currently working with a major poultry processor and a fish-feed manufacturer to explore use of poultry-byproduct meal as the primary protein source in sunshine bass diets. So far, the fish are readily consuming several experimental diets consisting of poultry byproducts and supplemental amino acids, but it is too early to tell whether those fish are performing as well as some being fed diets containing mostly fishmeal.

Rawles is also studying a diet containing meal from poultry meat, bone, feather, and blood instead of supplemental amino acids. These byproducts are high in protein and less expensive than feed-grade amino acids. Initial work indicated that the nutrients in these byproducts are highly digestible, but unfortunately the mix doesn't appeal to the bass. Rawles is investigating ways to increase the combination's palatability by adding fish solubles, betaine, or other ingredients.

Rawles says research is continuing on diets containing animal byproduct blends. "If any of the byproduct meal/amino acid-supplemented diets perform as well as the fishmeal diet, then we're on our way to a less expensive diet for hybrid striped bass," Rawles says.

[Excerpted from the June 2004 issue of Agricultural Research magazine.]

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