Improving Aquaculture Productivity One Gene at a TimeJohn Buchanan
Center for Aquaculture Technologies
Transgenics is a form of genetic engineering involving the addition of a new gene to the genome of an organism. The first significant reports on transgenic plants and animals appeared in the 1980s. Since then, a wide variety of transgenic organisms have been created, with introduced traits relevant for commercial production, biomedical models, and basic research. In transgenic plants, added genes have conferred improved commercially relevant traits such as pest resistance, herbicide resistance, drought tolerance, and improved nutritional value. Transgenic plants have been commercially deployed with remarkable success worldwide, and have been important tools in increasing crop yields. In transgenic animals, added genes have conferred improved commercially relevant traits such as faster growth, disease resistance, reduced environmental impact, and increased nutritional value. In contrast with transgenic plants, no transgenic food animals have been approved for commercial use. A rapid-growth transgenic salmon appears to be on the cusp of regulatory approval for commercial deployment.
Global production of food fish from aquaculture has grown substantially over the last 25 years. Per capita consumption of food fish was about 17 kg on an annual basis in 2008 (increasing from around 16 kg per capita in 2004), accounting for roughly 15.7% of the global population's intake of animal protein. Aquaculture currently accounts for roughly half of this food fish consumption, up from roughly 33% in 2000. Nevertheless, aquaculture in a global context is a young industry, with production increasing from less than 1 million metric tons in 1950 to greater than 50 million metric tons in 2008. With a stagnating global capture fishery, increasing per capita demand for fish, and an increasing population, increased aquaculture production is widely recognized as the only tractable solution for meeting growing demand for quality seafood. Accordingly, aquaculture will play a vital role in the supply of protein to a growing world population. According to FAO (Food and Agriculture Organization of the U.N.) projections, aquaculture productivity must double from 2008 levels by 2030 to meet the growing demand for seafood. This is a daunting task. The vast majority of cultured fish and shellfish species are only a few generations removed from wild relatives. Techniques including the careful application of transgenics to sustainably increase aquaculture productivity must be considered to make nutritious, high protein foods available to a growing population.
As a case study in the application of transgenics to improve aquaculture and food animal production, AquaBounty Technologies has been working with a line of rapid-growth transgenic Atlantic salmon (AquAdvantage® Salmon) for more than 15 years. These salmon, initially produced in 1989, possess a single additional gene, an extra growth hormone from a Chinook salmon under the control of regulatory elements from an antifreeze protein gene from the ocean pout. In addition to the challenges of developing a genetically engineered animal with improved production traits, challenges exist in securing the regulatory approvals necessary to deploy such technology. Genetically engineered food animals are regulated by the U.S. Food and Drug Administration (FDA) under the Food, Drug and Cosmetic Act. Significant resources over more than 10 years have been devoted to systematically addressing scientific questions relevant to FDA evaluation of this line. Studies assessing the safety, effectiveness, and nutritional composition of this line have been completed and submitted for FDA evaluation. Additionally, AquaBounty has committed to producing a triploid, all-female Atlantic salmon with a single copy of the GH transgene confirmed to be at the specific EO-1? genomic location. Triploidy is a procedure commonly used in fish to induce sterility. In addition, AquaBounty has proposed production of AquAdvantage salmon only in FDA-approved, physically contained, land-based facilities. This combination of biological and physical containment is designed to prevent any escape.
Summarizing a subset of regulatory findings, AquaBounty confirmed, by examination of over 7000 fertilized egg samples, that the commercial process for inducing sterility was 99.8% effective. In assessing target animal safety, in over 50 categories relevant to fish health (comprising behavior, external and internal appearance, histopathology, and hematology and blood chemistry), in more than 60 salmon, comprising over 5000 data points, no findings indicating transgene status caused significant health issues were noted. In assessing the nutritional and hormonal profile for body composition relevant to human nutrition, studies comprising over 70 salmon, in 59 categories (vitamins, minerals, amino acids, fatty acids, hormones), resulting in 4,000 data points examined revealed there were no significant differences between filets of the AquAdvantage salmon and commercially farmed salmon. In comparing AquAdvantage salmon to conventional salmon, no biologically relevant differences were detected in the levels of the gene product, or any endogenous metabolite or substance found in physiological pathways that could be impacted by that hormone. Additionally, AquAdvantage salmon contained the expected amounts of both omega-3 and omega-6 fatty acids in the appropriate ratio. No biologically relevant differences between food from AquaBounty's salmon and conventional Atlantic salmon were found.
The rapid-growth AquAdvantage Salmon has the potential to dramatically increase commercial production of salmon. Clearly, transgenics generally has the potential to rapidly increase animal agriculture productivity, as has already been demonstrated for commercially important crops. The scientific community has demonstrated the potential for transgenic technologies for animals, with the regulatory review process as the final remaining step. Transgenics is a valuable tool in the breeding toolbox that will be needed to increase food production in the face of an increasing population. The United States has the opportunity to lead the world both in the development of valuable transgenic food animals, and in the effective regulatory evaluation of transgenic animals for safe commercial application.