44 DECEMBER • WORLD AQUACULTURE • WWW.WAS.ORG crucial for crustaceans like shrimp and salmonids, where it serves as a natural pigment, imparting the characteristic pink or red color desirable to consumers (Jaseera and Kaladharan 2019). Beyond aesthetics, astaxanthin also acts as a powerful free-radical scavenger, protecting cells from oxidative damage and enhancing overall stress tolerance. Its role in bolstering the immune system and reproductive performance has also been widely documented in various aquaculture species. Another valuable bioactive found in some thraustochytrid strains is squalene, a triterpene with known antioxidant and immune-stimulatory properties. Squalene can contribute to cell membrane integrity and has been implicated in promoting beneficial lipid metabolism within the animal. Furthermore, thraustochytrids may also contain other beneficial components such as certain enzymes that aid digestion, phospholipids that enhance nutrient absorption, and potentially prebiotics that support gut health (Parrish 2024). By providing this diverse array of functional bioactives in addition to essential omega-3s, thraustochytrid-based ingredients contribute synergistically to the overall well-being of farmed aquatic animals. This comprehensive nutritional package supports not only growth and fatty acid profiles but also fortifies natural defenses, improves stress resilience, and ultimately leads to higher quality and more marketable aquaculture products. Efficacy in Aquafeeds: Performance and Sustainability The theoretical potential of thraustochytrids as a superior aquafeed ingredient has been extensively validated through numerous feeding trials across a diverse range of aquaculture species. These studies consistently demonstrate that thraustochytrid biomass, in various forms such as whole cell meal or extracted oil, can successfully replace a significant proportion, if not all, of the fish oil in aquafeeds without compromising growth, feed utilization, or overall animal health. For instance, research on Atlantic salmon, a species with high omega-3 requirements, has shown that diets incorporating thraustochytrid oil effectively replaced fish oil, maintaining comparable growth rates, feed conversion ratios (FCR), and protein and energy digestibility (Jaseera and Kaladharan 2019). Similar positive outcomes have been reported for tilapia, where thraustochytrid inclusion led to significantly improved weight gain, FCR, and protein efficiency ratio, alongside a higher DHA content in the fillet lipids, directly translating to enhanced nutritional value for consumers (Jaseera and Kaladharan 2019). Even in Pacific white shrimp (Litopenaeus vannamei) larvae, incorporating Schizochytrium meal into feeds has been shown to improve growth performance, highlighting its broad applicability across different aquatic taxa. Beyond growth metrics, the functional bioactives within thraustochytrids contribute substantially to the resilience and quality of farmed aquatic animals. Studies indicate enhanced immune responses and increased resistance to common pathogens in fish and shellfish fed thraustochytrid-supplemented diets. The antioxidant properties of compounds like astaxanthin further reduce oxidative stress, leading to healthier animals and potentially reduced reliance on therapeutics. Furthermore, the incorporation of thraustochytridderived pigments improves the coloration of species like salmon and shrimp, making the final product more appealing to consumers. From a sustainability perspective, the successful replacement of fish oil with thraustochytrid products marks a significant step forward. By reducing dependence on wild-caught forage fish, aquaculture can alleviate pressure on marine ecosystems, contribute to the recovery of wild fish stocks, and enhance its environmental stewardship (Parrish 2024). The closed-system cultivation of thraustochytrids also offers a more controlled and traceable supply chain, minimizing the risk of contaminants and ensuring a consistent quality of omega-3s, which is crucial for a responsible and future-proof aquaculture industry. Commercialization and Future Outlook The compelling scientific evidence supporting the efficacy and sustainability benefits of thraustochytrids has catalyzed their transition from research laboratories to commercial application. Several leading biotechnology companies have successfully developed and scaled up the production of thraustochytridderived omega-3 oils and meals for both human nutrition and animal feed markets. Notable examples include products like DSM’s DHAgold™ and Alltech’s All-GRich, which are now commercially available and being increasingly integrated into aquafeed formulations globally (Jaseera and Kaladharan 2019). These commercial ventures underscore the industry’s recognition of thraustochytrids as a viable and valuable alternative to fish oil. Despite this promising trajectory, broader adoption faces certain challenges. The primary hurdles often relate to the cost-effectiveness of large-scale fermentation compared to traditionally cheaper, albeit unsustainable, fish oil. While advancements in bioreactor technology, strain optimization through genetic engineering, and the utilization of inexpensive waste streams as substrates are continuously improving production economics, initial investment and operational costs can still be significant (Parrish 2024). Furthermore, navigating regulatory approvals in different regions and educating the wider aquaculture industry about the benefits and safety of novel feed ingredients remain ongoing efforts. However, the opportunities for thraustochytrids in aquaculture are immense. Continued research into novel strains with even higher LC-PUFA yields or diverse bioactive profiles will enhance their utility. Innovations in bioprocessing, including the integration of thraustochytrid cultivation into circular economy models where they utilize agricultural or industrial by-products as growth media, will further reduce costs and improve environmental performance (Yamasaki et al. 2006, Raghukumar 2008). As the aquaculture industry strives for greater sustainability and self-sufficiency, thraustochytrids are poised to play a pivotal role in reshaping feed Thraustochytrids reduce pressure on wild fish by offering a sustainable, land-free source of omega-3s. Grown using organic waste in closed systems, they support a circular bioeconomy and clean aquafeed production, without harming the ocean.
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