Research HighlightsImproving Sustainability and Cost Effectiveness of Soy-Based Aquaculture Diets
By Sarah Hill
Making fish a more sustainable animal protein is one of the many goals of the aquaculture industry. An Auburn University researcher has been working to systematically improve the sustainability and cost-effectiveness of diets for one specific fish species, the Florida pompano. The Florida pompano is a perfect fit for aquaculture, as it has a fast growth rate and commands a high price in retail settings.
“The Florida pompano has a small aquaculture footprint in the U.S. but is produced in large quantities in other countries. U.S. Soy is frequently exported to be fed to Florida pompano overseas,” says Allen Davis, professor at the Auburn University College of Agriculture’s School of Fisheries, Aquaculture and Aquatic Sciences.
Through a project funded by the Indiana Soybean Alliance, Davis has been studying Florida pompano diets where animal proteins comprised less than 10% of the diet and soy products made up around half of the diet. The soy products used in this study were high protein soybean meal with 58% protein and an ultra-low oligosaccharide meal. Many carnivorous fish struggle to digest oligosaccharides, so removing them can improve fish performance.
“Protein is one of the bigger costs in fish diets, so reducing the expense of protein by replacing it with soy is good,” Davis says. “We’re close to removing animal protein from many of our fish diets. Soybean meal is the most common replacement for animal protein, and it has advantages and disadvantages.”
The research team fed juvenile Florida pompano an experimental diet comprised of 55% soybean meal, 8% poultry meal, and 10% corn protein concentrate. After a 6-week growth period during the summer of 2022, they weighed the fish and took intestine and liver samples. Final fish weights and percent weight gain were lower than fish fed a commercial diet for the same length of time, but not significantly so.
“Most of the work done with Florida pompano is for the juvenile stages,” Davis says. “The animal is growing very quickly and if there is any nutritional stress, the fish will respond much quicker.”
One component of the research evaluated diets with soy from various sources. The 8-week study compared nine different diets, where solvent-extracted soybean meal was replaced with other types of soy products while keeping the protein level the same.
Davis and his team thinly sliced the gut and liver samples and examined them under a microscope, a process known as histology. The distal portion of the gut, the part closest to the end, did not display any signs of enteritis, an allergic response to soy, demonstrating that soy does not damage the gut in this fish species.
New soybean varieties that are marketed to soybean growers as high-value products could be used in marine fish feeds in the future, particularly to feed high-value species such as the Florida pompano.
“Newer soybean varieties are exciting to use for ultra-low saccharide meals and compounds,” Davis says. “We’re trying to find the limitations of using those soybean varieties in marine feeds.”
As this is only the first year of Davis’ project, he plans to continue the work to see if such high levels of soy in the diets lead to any adverse effects. He also aims to optimize inclusion levels and identify possible advantages of soy products such as low oligosaccharide meals, all with the goal of increasing the use of sustainable soy protein.
Additional Resources
The Soy Aquaculture Alliance – website
Published: Sep 18, 2023
The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.
