Submitted by Bob McDonald. "Golden Rainbow trout @ Id F&G Hatchery Hagerman."

(Courtesy of Bob McDonald)

TWIN FALLS • The aquaculture industry has been looking for alternatives to one of the main ingredients in fish feed for decades.

Listing ingredients that can replace fish meal is easy, but identifying those that are both effective in terms of both price and performance has been trickier.

University of Idaho researchers, working in conjunction with other institutions and commercial trout producers, have come up some experimental diets that meet those criteria. The key, explained Gary Fornshell, was identifying ingredients that are already commodities and hence are commercially available.

“We can evaluate a (potential) ingredient that has all the characteristics we want, but if it’s not a commodity, it’s not available to feed manufacturers,” said the UI extension aquaculture specialist.

Researchers developed two experimental diets, one plant-based and the other animal-based. Neither diet contained fish meal, but both used fish oil as an energy source. The experimental diets were tested in a laboratory, then in commercial raceways and finally, the resulting filets were taste-tested by both the aquaculture producers and the general public.

Not only did the research show that the experimental diets gave the same performance and feed conversion as a standard trout diet containing fish meal, but the end quality was also good.

“That shows that fish meal is not a requirement (for fish diets),” Fornshell said. “It’s a really good ingredient but it’s not a requirement — as long as we supply all the nutrients fish need in the quantity and quality that fish require.”

Fish are just like any other animal, he noted. They have nutrient requirements; they don’t have ingredient requirements. People, for example, need vitamin C but they don’t need citrus fruit.

The four-year study included extensive laboratory analysis before the experimental diets were fed to fish in a commercial setting. Both experimental diets contain less crude protein on an as-fed basis than the standard fish meal diet. That was done intentionally, Fornshell said.

Researchers based the experimental diets to provide what the fish needed and nothing more. Protein is the most expensive ingredient in feed. Even though some of the alternative ingredients in the experimental diets were nearly as expensive as fish meal, using less created cost savings that made the alternate diets competitive with the standard diet.

Researchers also developed a spreadsheet that producers and feed manufacturers can use to evaluate whether alternate ingredients are cost effective at market rates. Fornshell hasn’t updated his figures since corn and soybean prices began falling in early July, but the alternatives were cost-effective in the spring when commodity prices were higher.

Although the experimental diets are considered open formulas, meaning any feed manufacturer can use them, Fornshell expects adoption of the alternatives to be slow. Livestock producers are loathe to change diets they know are working and fish producers are no different.

But, if the price of fish meal or an alternate ingredient changes dramatically, both producers and feed manufacturers have the information to begin using the experimental diets immediately.

“It’s up to the feed manufacturers now,” Fornshell said. “They have the formulas and they are on top of commodity prices. If they get a request from a customer or if they are forced into these diets because of fish meal prices, they have the tools to make those feeds.”


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