SPECIAL STORY FEED & ADDITIVE MAGAZINE August 2023 53 To mitigate the demand for soy, the feed industry is working on alternative solutions, including greater use of local feed raw materials, upgrading and use of by-products from the food and grain crushing industries and investing in alternative protein technologies such as single cell proteins and insect meal, as well as upgraded vegetable proteins. A key technology that can also increase the efficiency of raw materials is the use of enzymes in feed formulation. Feed enzymes complement the animals' own digestive enzymes to ensure more of the diet is utilized. Enzyme use increases the digestibility of a variety of feed ingredients, reducing the reliance on fishmeal by improving the digestibility of plant-based feed ingredients and enabling greater flexibility in feed formulations. In addition, increased digestibility of the plant raw materials means that the environmental impact of aquaculture is also reduced, particularly with respect to phosphorus and nitrogen emissions. REDUCING ENVIRONMENTAL EMISSIONS Inland aquaculture represents more than 50% of total production, and farming in earthen ponds remains the most important method, dominated by carp, tilapia, catfish and shrimp. The expansion of land-based aquaculture has resulted in substantial environmental challenges affecting water, soil, biodiversity and climate. Many countries - notably China, the largest inland-aquaculture producer - have restricted the use of land and public waters for this purpose, which constrains expansion. At the same time global demand for salmon pushes marine production towards inland recirculating systems (RAS), offshore and deep sea closed systems due to environmental and health challenges. Regulators, water quality policies and health challenges are also pushing the warm water species sector to move into RAS. Authorities protect against eutrophication and acidification of water bodies by closely monitoring and regulating environmental emissions, such as phosphorus and nitrogen. With a growth in aquaculture production, good water management is crucial to enable sustainable growth in the next decades. In particular, management of phosphorus and nitrogen emissions is crucial to ensure the industry can grow sustainably. Phosphorus is a finite natural resource, and it is indispensable for agriculture and aquaculture production. It is an essential macro-mineral which has many important functions in the fish and shrimp body. The concentration of inorganic phosphorus in water is very low and in intensive aquaculture it must be supplemented in feeds to meet the optimum requirements for growth and well-being of the animal. Most of the phosphate in aqua feed is bound in a form inaccessible to the animals (phytate-P) and fishmeal alternatives, such as plant-based ingredients have high inclusion levels of phytate-P. This means that there is a potential for phosphorous discharge to the environment, leading to freshwater eutrophication and occurrence of undesirable off-flavors in the fillet. When feed is eaten by fish and shrimp it is metabolized into energy and nutrients used for growth and survival. As with all animals, there is waste produced by these normal metabolic processes and ammonia is the principal nitrogenous waste product produced by fish and shrimp from protein metabolism. Ammonia concentrations in the water increase as feed input increases in response to greater fish production, and the ammonia toxicity increases as temperature and pH increase. It is important to use feed with optimised protein levels, and it is crucial to improve the digestibility of the protein to reduce ammonia emissions. Appropriate measures, such as more precise feed formulations with containing lower amounts, but more digestible protein and the use of feed enzymes, such as protease, can result in a considerable decrease in the emissions of nitrogen compounds into water systems in aquaculture.
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