Importance of Feed Enzymes for Shrimp and Fish in Sustainable Aquaculture
Feeding enzymes to shrimps and fishes is one of the major nutritional advances in the aquaculture sector since last few years. Exogenous enzymes are now extensively used throughout the world as additives in animal diets. Also, supplementation with enzymes can help to eliminate the effects of antinutritional factors and improve the utilization of dietary energy and amino acids, resulting in improved performance of fish/shrimps (Farhangi and Carter, 2007; Lin et al., 2007; Soltan, 2009).
The primary purpose of enzyme application in feeds is to improve digestion. The digestive processes will work better and result shown in improved feed efficiency by providing an extra dose of enzymes. Further, aquatic animals are lack certain digestive enzymes during early development or throughout their life. In the case of fishes / shrimps lacking certain enzymes even in adulthood, application of these enzymes results in better utilization of nutrient fractions that are digested by the enzymes.
Enzymes are one of the many types of protein in biological systems. Their primary characteristic is to catalyze the rate of a reaction but is not themselves altered by it. They are involved in all types of anabolic and catabolic pathways of digestion and metabolism. Enzymes tend to be very specific catalysts that act on one or, at most a limited group of compounds known as substrates. Enzymes provide additional powerful tools that can inactivate anti-nutritional factors and enhance the nutritional value of plant-based protein in feeds. They provide a natural way to transform complex feed components into absorbable nutrients.
The addition of enzymes in feed can improve nutrient utilization, reducing feed cost and the excretion of nutrients into the environment.
Sources of Enzymes:
Enzymes are produced in every living organisms from the higher animals and plants to the simplest unicellular forms of life as they are essential for metabolic process. Microorganisms that generally involved in production of various enzymes are:
Bacteria: Bacillus subtilis, Bacillus lentus, Bacillus amyloliquefaciens and Bacillus stearothermophils.
Fungus: Triochoderma longibrachiatum, Asperigillus oryzae, Asperigillus niger and yeast
In animals, digestion of food is carried out by the animal’s digestive system and by microorganisms that inhabit the intestinal tract. The bacteria present in the gastrointestinal tract of fish/shrimp are potent producers of proteolytic enzymes. They may also produce cellulase moderately. The adding of live microorganisms to diets to produce enzymes is possible in specialty feed applications. Large scale commercial enzyme applications are rely on enzymes produced by microbial fermentation technology.
Factors contributing to use of Enzymes
Increase need for quality food grain for fish/shrimp
Increase need for quality animal products /by –products
Search for alternate sources of food with better nutritive value
Economic margins (reduced cost: benefit cost)
Quick realization of profits
Rise of environmental awareness
Types of Enzymes available for Fishes / shrimps
Many enzymes have been used in fish/shrimp nutrition over the past several years which includes cellulose, (β-glucanases), xylanases and associated enzymes like phytase, proteases, lipases and galactosidases. Enzymes in the feed industry have mostly been used for culture animals to neutralize the effects of the viscous, non-starch polysaccharides in cereals and other food grains.
Action & Benefits of Feed Enzymes:
Reduces in digesta viscosity
Enhances digestation and absorption of nutrients especially fat & protein.
Improves Apparent Metabolizable Energy (AME) value of the diet
Increases feed intake, weight gain and feed gain ratio
Reduces ammonia production
Improves nutrient Digestibility.
Endogenous enzymes found in the fish/shrimp digestive system which help to break down large organic molecules like starch, cellulose and protein into simpler substances.
The carbohydrate digestion improves by using microbial enzymes. Addition of exogenous carbohydrates enzymes to feed increase utilization of unavailable dietary carbohydrates. High levels of non-starch polysaccharides (NSP) such as cellulose, xylans and mannans reduce the nutritive value of many plant ingredients. Intestinal enzymes to digest these carbohydrates are not produced by most animals.
Enzymes and Function
Application of enzymes is probably a solution to high larval mortality in aquatic animals. The intestinal tract of aquatic animal larvae is shorter and relatively undeveloped when compared to that of the adults. The larval feeding would benefit from enzyme application.
Impact of Feed Enzymes on Sustainable Aquaculture
Successful and sustainable aquaculture depends on economically viable and environmental friendly feeds. Feed is the major operational cost involving 50 to 60 per cent of the total cost in intensive farming. The major feed ingredient, fishmeal, is expensive and there is increasing competition with other livestock industries for the available supply.
Enzymes have been used in aqua feed because they are natural products of fermentation and therefore pose no threat to fish / shrimp health and pond environment. Enzymes reduces high phosphorus output problems in pond environments. It reduces ammonia levels in pond water.
Enzymes can therefore play an important role in formulating eco-friendly aquafeeds. Currently, the use of enzymes is able to reduce fishmeal inclusion by around 5 per cent in most aquafeeds with potential for more as techniques are refined. This may help to reduce the demand for fishmeal from the aquaculture sector in coming years.
The use of enzymes as a feed additive has rapidly expanded and significant instrument for the use in aqua feed. Although the economic and social benefits of enzymes have been well established, the future of feed enzymes is a bright one in aquaculture industry.