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Aquaculture recently are known as one field that very important as a source of animal protein and gourmet cuisines, job opportunities, and foreign currency for developing countries. 91 percent of the world's total aquaculture production was produce by Asian countries as nine Asian countries being in top ten aquaculture production. Aquaculture played an important role as it will be able to solve the food problem and crisis in the future (Liao et al, 2009) . Problem such as pollution that occur because of the arising deposition of faecal matter, partially digest feed and uneaten food can be minimize by the most effective way in the aquaculture industry especially in diet formulation.
In the aquaculture system, almost the cost of feed was around 30% to 60 % of the operational costs of the farm including its management (Ng, 2002). In formulated diets, fish meal dominantly becomes the major source of dietary protein in the diets and protein always becomes the most expensive dietary component. Then, for these reason some of researcher have done some study by find the other alternative such as plant protein as the source of protein as the replacement of the animal protein (El-sayed, 1999) and it is reported that soy bean become the most commercial success as protein source compare to the other plant protein.
Tilapias are an important component of subsistence fisheries for thousands years but have gained prominence in recent years in areas since they are not endemic. Introductions of better performing tilapia species and the development of techniques in managing led to success in tilapia farming.
Tilapia is one of the members in family Cichlidae but recently there were some attempts to change the classification of tilapia species. Tilapia was classified into three genera that are called Oreochromis, Sarotherodon and Tilapia. Sarotheradon and Oreochromis are mouthbreeders where the female keep the egg, larvae and fry inside their mouth to protect them until the fry are big enough, able to feed and swim independently before released them. Sarotheradon and oreochromis are different from Tilapia since they incubate and guard the egg in the nest (Popma and Masser, 1999; Chapman, 2002). The spending energy of parent to protect their progenies is quite a lot for tilapia (Mires, 1995). The mature size of tilapia just around 8-10 cm body length at very young age and mostly they have an ability to spawn every 6-8 weeks (Lovell, 2002).
9 species from 70 species of tilapia are used in aquaculture worldwide (FAO, 2002) and Nile tilapia (Oreochromis niloticus) become the most cultured species and it significantly increased the global tilapia production in aquaculture industry compare to Blue tilapia (O. aureus) and Mozambique tilapia (O. mossambicus).
Tilapia is good for aquaculture due to their positive characteristics such as ability to being cultured in variety of environment such as fresh, brackish or salt water. Tilapia also tolerant to crowding and can survive in degraded water quality and responds well to the formulated diets. They also grow rapidly either in natural or man-made pond, cages and other types of culture. It is an advantage in culturing tilapia since tilapia responds well to artificial feed that contain high percentage of plant proteins.
2.3 Nutrient Requirement
It is not surprising that nutrition in fish and other aquatic animal become one of the most important research and studies in order to reduce the higher operating cost in aquaculture industry. Nutrient are required to stay alive, healthy and ability to grow rapidly. In the culturing fish it is important to know that fish eat enough and all the feed given is utilized and consumed by the fish efficiently. Formulated diets must satisfy nutritional requirement in the term of protein (essential amino acids, EAA) lipids (essential fatty acids, EFA), vitamins, mineral and also energy (Satoh, 1991)
Tilapia is generally herbivorous but some species are omnivorous (Stickney, 1993). The requirement nutrient for tilapia is similar as the other warm-water finfish (Luquet, 1991). The most proper balance of diet contain an ingredients such as protein, carbohydrate, minerals, vitamins, lipids, fiber and some other ingredient. A proper and well diet formulation is the most important factor to enhance the optimum effect toward the cultured organism.
The nutrient requirement are different between species and different stage of it life cycle within species. The fry and fingerling of tilapia require a diet with higher protein, lipids, vitamins and minerals but lower carbohydrates. They need higher protein, lipids, mineral and vitamin for muscle, internal organs and bone developing. An excellent reviews of tilapia nutrition had been done by Jauncey and Ross, (1982); El-Sayed and Teshima, (1991) and Stickney, (1996).
2.4 Protein and Amino Acid
Protein is very important constituent of diet as protein are the essential nutrient of building material for growing, maintaining life, good for health and for the production of enzymes, hormone and other things for normal metabolism (Boonyarat, 1999). Protein is higher molecular compound within the carbon, oxygen, hydrogen and nitrogen. Protein was composed of a lot of amino acids that linked by peptide bond which make the protein in a chain. They are held by other bond such as disulfide bridges, hydrogen bonds and forces called Van Der Waals forces. Amino acid is the building block for protein compound.
The quantities protein that required by O.niloticus, O.mossambicus, O.aureus and also T.zilli have recently reviewed and showed that tilapia requires 30% to 35% of protein (De Silva at al., 1995). However, there are several factors that influence protein requirement of fish include the age and size of fish, dietary protein and energy content, water quality and the culture conditions (El-Sayed, 2004). The maximum requirement of protein for tilapia during the larvae stages are relatively higher from 15% up to 50% (De Silva and Anderson., 1995) compared to the other stages the fry and fingerlings protein requirement are higher as it ranges 40% to 45% for the fry and 30-35% for fingerlings for the best performance (El-Sayed & Teshima, 1992; Wang et al., 1985; De Silva & Radampola, 1990). The brood stock needs almost 35%-45% protein (Al Hafedh, 1999; El-Sayed et al., 2003).
Fish meal always come first as the major protein source in the diet for cultured species. The price of fish meal is really expensive compared to the other animal or plants protein source. Fish meal mostly made from the marine capture fish that were grouping as trash fish. In 2006, nearly 33 million tonnes of the world capture fish was turned into the fish meal and fish oil (FAO, 2008). The fishes and the procedure of making fish meal becomes the most important thing that will indicate the quality of fish meal. Other than fish meal, soy bean meal becomes the most common ingredient as the protein source in diet. Soybean meal were use as it have high protein composition and have several amino acid which is have better profile compare to the other plant protein source such as corn and cottonseed.
An amino acid is composed of amino group (-NH2) and carboxyl group (- COOH) and both of them soluble in water. Some amino acid will become another compound by change their structural and some amino acid can use for protein synthesis. Polypeptide was called for amino acid in the larger group of them that is will lead to the formation of protein. Amino acid occur naturally more than 200 types in nature but only 20 amino acids are incorporated into the body protein. 10 amino acids out of the 20 amino acid are the essential amino acid (EAA) for the fish, as they cannot be synthesized because of the complex building. So, essential amino acid (EAA) must be provided in the fish diet in order to give optimal effect of the diet. The 10 quantitative essential amino acid that required for Nile tilapia are reported is arginine, histidine, isoleucine, leucine, lysine, methionine, methionine + cystine phenylalanine, phenylalanine + tyrosine, threonine and trytophan (Santiago & Lovell, 1988). Table 2.4 show the amino acid requirement for Nile tilapia but mostly essential amino acid is required in the same in most species (NRC, 1993).
Table 2.1: The quantitative essential amino acid requirements for Nile tilapia
10 Quantitative essential amino acid requirements for Tilapia1
Methionine + cystine2
Phenylalanine + tyrosine3
1Expressed as the percent of dietary protein
2Cystine included as 0.54% of the protein.
3Tyrosine included as 1.79% of the protein.
Sugar or carbohydrate is an essential components and the most abundant class of organic compound in all living organism. Carbohydrate is an organic compound that made up from the three elements such as carbon, hydrogen and oxygen. Carbohydrate can be classified into monosaccharide; oligosaccharide and polysaccharide. Monosaccharide was the basic unit of the carbohydrate that originates from photosynthesis process as the product and the building block of monosaccharide will form oligosaccharide and polysaccharide.
Starches that occur in the forms of granules in plants cell are composed of amylose that soluble in water and amylopectin. Glucose, maltose, and sucrose dietary carbohydrate gives the best performance followed by dextrin and fructose (De Silva, 1995). The utilization of carbohydrate by fish varies due to the complexity of the carbohydrate compounds. Dextrin that become one of the ingredients in diet formulation are the water soluble of starch breakdown. Although, in the wild habitat fish only able to digest very small content of carbohydrate in their natural diet but the breakdown of protein and certain amino acid were done by them to gain energy.
The most important carbohydrate is glycogen, glucose, lactose and pryurate (Black et al., 1961). Tilapia has good utilization of carbohydrate and has better utilization compared to red sea beam and yellow tail (Anderson et al., 1984). O.Niloticus and T.zilli show better performance with the higher level of carbohydrate (dextrin) proximately 40% in the formulated diet (El-Sayed and Garling, 1988). Warm-water species Nile tilapia (Popma, 1982) and channel catfish (Wilson and Poe, 1985) able to digest greater dietary carbohydrate compare cold-water species that show by rainbow trout (Cho & Slinger, 1976).
Vitamin is an organic compound that acts as cofactor in substrates in the metabolism of the cell. The present of inadequate amounts of vitamin in feed may cause some serious metabolic disorder, increase disease infection and some will lead to mortality. It is very difficult to trace and detect the deficiency of vitamin (Werner, 1989).
Same as amino acids, vitamin also one of an essential ingredient in feed and must be supplemented in the feeds since some of them only can be synthesized in small quantities by fish. Vitamin played role in the metabolism of the cell. Vitamin is not essential to all animal since there is some enzyme activity within the digestive tract in the animal. The important of vitamin to fish as it will prevent the diseases, promote the growth and maintain the health of the fish (Nakagawa et al., 2007).
Vitamin can be divided into fat-soluble and water soluble vitamin. It is having been showed that 4 fat-soluble and 11 water soluble vitamin is essential to fish (Bureau and Cho, 2004). The majority of vitamin that required for fish have not determined yet since it is not widely study. Vitamin C, vitamin E and vitamin B recently achieve more concern in the requirement of nutrient by researcher. Studies have showed that vitamin have ability to improved the health and fish quality, stress tolerance and disease resistant (Lim and Webster, 2001; Lim et al., 2001).
Fish can be stress because of the crowding condition and declined the water quality and one way to minimize the stress of fish by supply vitamin in their feed.
Mineral are inorganic elements that can be divided into macro-minerals or major minerals and micro-minerals or trace minerals. Macro-minerals such as calcium (Ca), phosphorus (P) magnesium (Mg), potassium (K), sodium (Na), chlorine (Cl) and sulphur (S) that usually required in large amount. Micro-minerals such as iron(Fe), copper (Cu) , manganese (Mn), cobalt (Co), molybdenum (Mo), Chromium (Cr), selenium (Se), Fluorine (F) and nickel (Ni) only required in small amount same as enzyme or hormone (De Silva and Anderson., 1995).
Fish not able to absorb 100% mineral from but mineral also absorb from their environment (NRC, 1993). Marine fish have an advantages compare to freshwater fish since marine water contain a lot of mineral compare to freshwater. Mineral needed for fish because mineral are provide the structural element for tissue formation, maintain osmotic pressure and take part in some metabolic processes. Calcium, phosphorus and magnesium are largely found in the muscle and skeleton tissue. Mineral requirement by tilapia are similar to some other warm-water finfish species (Lovell, 2002).
Enzymes are protein that acts as highly effective biological catalysts that provide nutrient that necessary for life. Enzyme activity able to increases the rate of chemical reaction in digestibility of nutrient in the complex macromolecules and improve the utilization of nutrient that uptake by animal. The most common use of enzyme contains wheat or barley in the poultry diet. Enzyme also can promote the digestibility complex macromolecules.
Enzyme reaction can be describe as a key and unlocks processes. The reaction of enzyme is very specific as it only able to catalyze the specific substances. An enzyme act as the key that is have specific structure shape and it will bind to a specific part of the compound or substrate.
There are many enzymes that already marketed today such as Reap, enzyme that introduce by Prince Agri Product which has ability to improve starch digestibility. GhemGen Corporation found Beta-mannase in Hemicell have ability to break down the sticky carbohydrate in soybean meal as soybean meal have small portion of anti-nutritive fibre that inhibits the utilization of feed by poultry. Avizyme 1502 marketed by Danisco that can be used to improve the maize digestibility and other kind of enzyme that available in market today (Terrence O' keefe, 2005).
Â The use of enzyme complex in order to improve performance in animals is topical in most countries with a developed livestock industry. Allzyme VegproTM that marketed by Alltech Biotechnology Corporation provide a higher quality of diets that increases the digestibility of amino acids, soybeans, canola, safflower, sunflower and other source of vegetable protein. The enzyme complex utilized was Allzyme VegproTM, containing the enzymes protease, amylase and cellulose. The increase of digestibility was performed because the present of enzyme those make up Allzyme VegproTM. Ng et al.,(2002) show that used of enzyme in fish feed has potential to reduce the cost of feeding.
Recent studies that have been done to ruminant animal such as chicken and pig that feeds the diets that contain or treat with the Allzyme VegproTM show resulted better performance and nutrient uptake (Leite, 2008; Zobac, 1998). Other studies that done by (Ng. et al, 2002) showed that there is a great potential of reducing the feed cost in feeds as pretreatment of palm kernel meal with enzyme Tilapia have show better performance compare to control diet. In other studies resulted that the enzyme activities in intestine are increasing within the increasing the enzyme (protease and amylase) level (Lin, 2007). The broiler chicken that feed within enzyme composition more efficient in chicken performance (Raza, 2009).
Energy has been released from the metabolism of oxidation of carbohydrate, lipids and protein. Energy commonly expresses as heat units known as calorie. A calorie (cal) defined as the amount of heat that required increasing the temperature of 1 g of water by 1Â°C. Now, joule (J) were became accepted SI unit of energy (1 cal = 4.184 J). The energy that intake from the organism are depend on its chemical composition but there is some gross energy will loses through gill excretion (GE) and urine excretion (UE). Loses of GE and UE of fish are smaller compared to birds and mammal (NRC, 1993). Two methods use to know the energy requirement, which is oxygen consumption and heat production of the fish.The Nile tilapia (Oreochromis niloticus) fry need about 400kcal/100 g and 45% of protein level under the laboratory conditions (El-Sayed & Teshima, 1992).