Growing aquaculture industry needs better fish nutrition – AgriLife Today


The United States is the leading producer of hybrid striped bass, and a Texas A&M AgriLife team is working to improve fish health, growth, and productivity by developing effective nutritional strategies to replace fishmeal and other protein feeds in the diet of farmed bass.

Fish from the Aquaculture Research and Education Center are among the grant-funded studies. (Texas A&M AgriLife photo by Laura McKenzie)

Aquaculture is the fastest growing agricultural business in the world. The field is expected to continue to grow to provide seafood for the world’s growing population.

Some species of fish produced in aquaculture, such as omnivorous catfish and carp, consume diets without fishmeal. However, more carnivorous species such as hybrid striped bass have traditionally been fed a considerable amount of fishmeal, which is a highly nutritious but expensive marine food.

The U.S. Department of Agriculture’s National Institute of Food and Agriculture awarded two grants totaling $1.15 million for the team’s studies of hybrid striped bass. The work will be led by Guoyao Wu, Ph.D., professor emeritus of the College of Agriculture and Life Sciences and a member of the Texas A&M AgriLife Research Faculty in the Department of Animal Science at Texas A&M.

Delbert Gatlin, Ph.D., Regents Professor in the Department of Ecology and Conservation Biology, Bryan-College Station, partners with Wu for a study titled “Biosynthesis and Nutritional Roles of Glycine in Hybrid Striped Bass” . On the second study, titled “Impact of Dietary Glutamate on the Development of Gut Mucosal Immunity in Hybrid Striped Bass”, Wu will collaborate with Mike Criscitiello, Ph.D., professor of veterinary pathobiology and associate dean for research and graduate studies in the College of Veterinary Medicine and Biomedical Sciences.

Limited supplies drive interest in plant-based alternatives

Generally speaking, the production of fishmeal and fish oil is environmentally and ecologically sustainable, Gatlin said. Their production hasn’t varied much in recent decades, and both have pretty good life cycle assessments compared to other food resources.

“However, their supplies are limited, so while global aquaculture is expected to continue to grow, the costs of these marine ingredients are expected to rise,” he said. “Thus, there will likely be a greater need to replace larger servings of fishmeal and fish oil in the diets of various fish species, especially those with more carnivorous natural eating habits. Thus, our project should allow greater flexibility in formulating diets to meet the nutritional needs of hybrid striped bass without relying on fishmeal or other animal feeds.

Wu said fishmeal has traditionally been used as the main protein food in hybrid striped bass diets, but due to growing demand and escalating costs, there is growing interest in using plant-based protein. such as soy flour to replace fish meal in aquafoods. But success has been variable, he said.

“We found that glycine, the most abundant amino acid in the body of fish and fishmeal, is relatively low in plant protein,” Wu said. “Based on the results of our preliminary study, we believe that dietary glycine plays an important role in the growth of hybrid striped bass by maximizing protein synthesis, antioxidant capacity and creatine production in their tissues.”

Glutamate, the second most abundant amino acid in the body of fish and fishmeal, works with glycine to promote metabolic processes. Collectively, scientists believe that glutamate and glycine should be considered “functional amino acids” in animal feed.

Glutamate and glycine “are the least expensive amino acids, yet they show great promise as cost-effective feed additives,” Wu said. basic research into the efficient production of high quality animal protein for human consumption.”

Glutamate supports gut health

Wu and Criscitiello said their study is a logical extension of their long-standing interest in nutrition and amino acid metabolism as well as immunological defenses in animals.

“These studies will not only provide crucial information for more efficient aquaculture feeds, but they will also help elucidate fundamental interactions between mucosal nutrition and immunology that are conserved in vertebrates, from fish to mammals,” Criscitiello said. “It will help us understand how our gut immune system has evolved to manage beneficial microbiota while preventing infectious disease.”

Amino acids are the building blocks of proteins and also have other important biological functions, such as helping animals defend themselves against infectious microbes. The mucous tissues of the intestine serve as a natural barrier to defend aquatic – and terrestrial – animals against harmful bacteria, parasites and viruses. Thus, the gut’s ability to resist infectious agents outside the body is crucial for the health and survival of fish.

Glutamate is a precursor to glutathione, an abundant antioxidant substance and a major metabolic fuel for the intestinal mucosa. Thus, glutamate is crucial for intestinal integrity and health. However, for more than a century, glutamate was considered a nutritionally non-essential amino acid in fish and other animals.

“Based on the results of our preliminary study, we believe that dietary glutamate plays an important role in the development of the gut immune system in hybrid striped bass,” Wu said. production of anti-infective and antioxidant molecules by immune cells in the intestinal mucosa of fish.”

Additionally, he said, the ability of mucosal immune cells to use glutamate for energy production increases with age as the cells mature.

“Our findings will have a significant impact on U.S. aquaculture by generating fundamental new insights into glutamate to improve gut mucosal health and hybrid striped bass survival,” Wu said. “The results will also provide a novel method nutritional value for the use of glutamate as an adjuvant in the development of vaccines for fish.”

Glycine helps convert food into protein

Besides glutamate, fish also need a large amount of glycine for their growth and health. And like glutamate, glycine has long been considered an essential nutrient in animal diets.

However, Wu said, glycine intake in fish diets can play a crucial role in converting food into body protein.

He and Gatlin will determine how glycine and creatine are synthesized in different fish tissues. This team will also investigate the roles of glutathione and creatine in mediating the effect of dietary glycine to improve growth, antioxidant responses, gut integrity, metabolic health and immunity in hybrid striped bass.

Additionally, they will determine the role of the target rapamycin, which is the master regulator of protein synthesis, and autophagy/proteasomes in mediating the effect of dietary glycine to promote protein synthesis and inhibit proteolysis in fish tissues.

“Skeletal muscle is the primary site of creatine synthesis from glycine in hybrid striped bass,” Wu said. “Glycine activates the cell signaling pathway target rapamycin to promote protein synthesis in skeletal muscle, while reducing intramuscular protein breakdown via autophagy/proteasome pathways, which promotes muscle growth.

According to the preliminary results, Wu said, “we believe that supplementing 2% glycine in soybean meal diets can replace 45% fishmeal in hybrid striped bass diets.”

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