42 SEPTEMBER 2023 • WORLD AQUACULTURE • WWW.WAS.ORG nutritional advancements in the aquaculture sector in the last few years. Exogenous enzymes as feed additives are now extensively being used throughout the world in animal diets. Supplementation with enzymes can help to eliminate the effects of anti-nutritional factors and improve the utilization of dietary nutrients, resulting in better performance (Farhangi and Carter 2007, Soltan 2009). The primary purpose of enzyme supplementation in aquafeeds is to improve digestion, resulting in enhanced feeding efficiency and nutrient utilization. Aquatic animals may lack certain digestive enzymes during early phases of development or throughout their life. When fishes or shrimps naturally lack certain enzymes even into adulthood, dietary addition of these enzymes results in better utilization of nutritional constituents digested by the enzymes. Main Concerns Related to Enzyme Supplementation A number of concerns must be addressed for the aquafeed industry to widely embrace enzyme application as a way to improve feed performance. These include: • The effect of temperature on the stability of enzymes applied in the feed prior to pelleting or extrusion. • Leaching loss in water when feeds are coated with enzymes after thermal processing. • The effectiveness of microbial enzymes when supplied to poikilothermic aquatic animals is also an important concern. Sources of Enzymes As they are essential for metabolic processes, enzymes are produced in almost every living organism from the simplest unicellular forms of life to higher animals and plants. Microorganisms are commonly employed for the production of various enzymes, including bacteria such as Bacillus amyloliquifaciens, B. lentus, B. subtilis and B. stearothermophils, and fungi such as Asperigillus oryzae, A. niger, Triochoderma longibrachiatum and various yeasts. In animals, digestion of food is accomplished both by the physiological digestive system and by microorganisms that inhabit the intestinal tract. The bacteria colonizing the gastrointestinal Fishmeal is a preferable source of protein for fish feeds because of its good nutritional value, especially its high protein quality (NRC 1993). However, it has limited availability and high cost in many countries (Lin et al. 2007). The high cost factor is especially relevant to the high dietary protein requirement of carnivorous fishes. Several alternative feed ingredients such as grains and oilseed byproducts are the most promising protein and energy sources for aquafeeds in the future (Hardy 2000). However, the utilization of such plant-derived ingredients has been limited because of the presence of a wide variety of antimetabolites or anti-nutritional factors (De Silva and Anderson 1995). These feed ingredients from plant sources can contain compounds that either the fish/shrimp cannot digest or which hinder the digestive process because the species in question cannot produce the enzymes required for degradation. Although many plant based-materials are of low palatability, anti-nutritional factors are the most serious concern in completely replacing fishmeal in feed formulations. Anti-metabolites have deleterious impacts on the digestion of feed and its conversion efficiency. There are many categories of anti-nutritional factors associated with the most widely used plant materials, like trypsin inhibitor proteins, non-starch polysaccharides (NSP), glucosinolates and phytate. Heat treatment and water soaking are two common detoxification methods of these anti-nutritional factors. Exogenous enzymes are often incorporated in animal feeds to enhance the nutritive value of plant-based feed ingredients (Buchanan et al. 1997). Enzymes are among several common types of proteins in biological systems. They can catalyze the rate of a reaction, but are not themselves altered by it. Enzymes regulate all types of anabolic and catabolic pathways of digestion and metabolism, acting specifically on one or, at most, a limited group of compounds known as substrates. Enzymes act as additional powerful tools to inactivate anti-nutritional factors and enhance the nutritional value of plant-based ingredients in feeds. They bring about the transformation of complex feed components into simple absorbable nutrients. The supplementation of enzymes in feed can improve nutrient utilization efficiency, reducing feed cost and the release of unutilized nutrients into the environment. Feeding enzymes to shrimps and fishes is one of the key Utilization of Exogenous Enzymes in Aquafeeds Mir Ishfaq Nazir, Irfan Ahmad Bhat, Ngairangbam Sushila and Jaffer Yousf Dar Enzymes are among several common types of proteins in biological systems. They can catalyze the rate of a reaction, but are not themselves altered by it. Enzymes regulate all types of anabolic and catabolic pathways of digestion and metabolism, acting specifically on one or, at most, a limited group of compounds known as substrates. Enzymes act as additional powerful tools to inactivate anti-nutritional factors and enhance the nutritional value of plant-based ingredients in feeds. They bring about the transformation of complex feed components into simple absorbable nutrients. The supplementation of enzymes in feed can improve nutrient utilization efficiency, reducing feed cost and the release of unutilized nutrients into the environment.
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