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Aquaculture Feed and Fertilizer Resources Information System
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First feeding Nile tilapia juveniles that do not have access to live food display morphological anomalies in their digestive system that reduces their ability to digest, absorb and assimilate nutrients efficiently, resulting in low weight gain that may persist through adulthood (Bishop and Watts, 1998). The use of live food can therefore reduce the time required to complete organogenesis and the early completion of a functional digestive system thereby maximizing the growth potential of the tilapia fry. The practise of rearing juveniles in smaller ponds or in hapas prior to ongrowing is universal. Natural productivity in nursing ponds or hapas provides the necessary live food for the growth of tilapia. Organic and/or inorganic fertilizers can be used to stimulate the production of phytoplankton which is the main live food consumed by tilapia during these early stages. Therefore, no specialized separate live food production facilities are needed in the culture of tilapia although there are reports that many tilapia farmers produce zooplankton such as Daphnia and Moina and use them as supplementary feed for fry and fingerlings for increased production. High quality formulated feeds are used to achieve high yields and large sized fish (600-900 g) within a short period of time. The maximum size at harvest of Nile tilapia reared in ponds that are only fertilized is generally less than 250 g after 5 months of ongrowing. Under semi-intensive farming systems, most tilapia farmers in Asia fertilize their ponds and use formulated feeds. However, in intensive pond and tank culture systems or in cages, tilapia farmers mainly depend on commercial pelleted feeds. The nutrient inputs used and the yield and weight of tilapia at harvest in several Asian countries are summarized by Dey (2001). In terms of pond yields, Dey (2001) reported that overall, the average yield of pond farming in Taiwan, Province of China is very high (12 to 17 tonnes/ha) while ponds in Bangladesh, China, the Philippines, Thailand and Viet Nam produce around 1.7, 6.6, 3.0, 6.3 and 3.0 tonnes/ha, respectively.
Tacon, Hasan and Subasinghe (2006) conservatively estimated that the global production of industrially manufactured aquafeeds in 2003 was about 19.5 million tonnes with projections of 27.7 million tonnes by the year 2010. Tilapia feeds accounted for about 8.1 percent of global aquafeed production in 2003. Commercial tilapia feeds are mainly dry sinking pellets and extruded floating pellets. Production estimates for farm-made tilapia feeds are not available as these are usually site specific and dependent on locally available feed ingredients. In countries such as the Philippines, on-farm feeds are not very popular as tilapia farmers find it more convenient to purchase formulated feeds from feed companies. A brief summary of the advantages and disadvantages of various feed types is provided in Table 9.
The main issue in formulating feed is to meet the protein and essential amino acids (EAAs) requirements of the species. Fishmeal is generally the preferred protein source because of the high quality of the protein and its EAA profile. However, fishmeal is generally expensive and is not always available. Nile tilapia can be fed with a high percentage of plant proteins. It is economically judicious to replace fishmeal with alternative protein sources including animal by-products, oilseed meal and cakes, legumes and cereal by-products and aquatic plants. Most of these ingredients are deficient in some EAA and hence require supplementation or be compensated with other feedstuffs. Although most of the oilseed cakes/by-products are generally deficient in lysine and methionine, blending of different oilseed cakes often provides balanced amino acid profile. However they contain many anti-nutritional factors (such as gossypol, glucosinolates, saponins, trypsin inhibitors etc.) which limit their use in compound feeds or require removal/inactivation through specific processing (such as heating, cooking etc). There are also several non-conventional protein sources that may be suitable for O. niloticus such as silkworm pupae, snails, earthworms, Spirulina, corn and wheat gluten, almond cake, sesame cake, brewery waste, etc. Feed ingredients of plant and animal origin used in the formulation of tilapia feeds with their general nutritional values and other relevant information are provided in Tables 10-11-12. The maximum inclusion level of each feedstuff that can be used in tilapia feeds is dependent on several factors such as the level of dietary protein, how the feedstuff was processed, life stage of the fish, economics, availability, etc. Some suggestions for their maximum dietary inclusion based on the data obtained from tilapia and other herbivorous fishes are included in Tables 10-11-12. However, it should be noted that these are only suggestions and with research data coming from more recent feeding trials and the advancement of processing techniques, many of these recommendations would need to be revised in future. For example, with better processing techniques, feedstuffs such as soybean meal and poultry by-product meal can now be included at much higher levels in tilapia feeds than previously recommended. A review of various alternative dietary protein sources for farmed tilapia and its replacement potential for fishmeal in tilapia diets is provided by El-Sayed (2006). A summary of the tested and recommended levels of different protein sources for Nile tilapia compiled by El-Sayed (2006) is listed in Table 13.  The ingredients used in the formulation of farm-made tilapia feeds vary regionally. In Thailand, a typical feed formulation for herbivorous fish may include fishmeal (16 percent), peanut meal (24 percent), soybean meal (14 percent), rice bran (30 percent), broken rice (15 percent) and vitamin/mineral premixes (1 percent) (Somsueb, 1994). Some examples of farm-made feed formulations for tilapia at various life stages under semi-intensive farming conditions in Thailand are listed in Tables 14. In some countries (e.g. the Philippines) farm made feeds are not commonly used, despite the fact that feed accounts for up to 79 percent of total operating costs. The main reason why farm made feeds are not commonly used in the Philippines is because of erratic supplies of raw materials, high capital requirements and the lack of equipment specifically designed for small scale farmers (www.adb.org).  The ingredient composition and formulation of commercial tilapia feeds is usually the proprietary of the manufacturer. However, in some cases, due to labelling laws, the list of ingredients used is indicated on the feed bag but usually inclusion rates are not provided (Figure 12). For example, tilapia feeds produced by San Miguel Foods, Inc., in the Philippines contain the following ingredients: corn, soybean meal, fishmeal, poultry by-product meal, brewer’s yeast, corn gluten, rice bran, copra meal, brewer’s grain, wheat pollard, molasses, vegetable oil, salt, limestone, dicalcium phosphate, ethoxyquin, L-lysine, DL-methionine, binder, mould inhibitor, virginiamycin (Cruz, 1997).
Full disclosure of ingredient formulation is usually given only in experimental tilapia diets and published in various journals but these generally do not reflect the typical commercial tilapia feeds used in intensive farming systems. A typical commercial tilapia starter feed in Malaysia may contain the following formula: fishmeal (15 percent), meat meal (5 percent), soybean meal (20 percent), groundnut meal (10 percent), rice bran (10 percent), wheat middlings (15 percent), corn/broken rice/cassava (15 percent), vegetable/fish oil (4 percent), dicalcium phosphate (2 percent), vitamin premix (2 percent) and mineral premix (2 percent). Other examples of commercial tilapia feeds produced in South East Asian countries and in other parts of the world are listed in Tables 15-18 (Link to: Table 15, Table 16, Table 17, Table 18).
Commercial tilapia feeds are generally available in three or four types with different nutrient specifications depending on life stage or fish size, i.e., pre-starter, starter, grower and finisher feeds. For the Charoen Pokphand Group which is one of the largest industrial animal feeds manufacturer in the world, their tilapia feeds (used in many Asian countries) contains 35-40 percent protein for fish less than 10 g and 20-28 percent protein for fish >300 g (Table 19). Least-cost programming is widely used for feed formulation and is dependent upon available ingredients and the nutritional requirements of the fish. For tilapia feeds in Asia, the carbohydrate/energy source is largely dependent on locally available feedstuffs. Feed formulators should also consider formulating tilapia diets based on a digestible/available nutrient basis as more data from research becomes available for Nile tilapia (Koprucu and Ozdemir, 2005). Feed additives of various types are included in small amounts in most feeds to perform various functions. A list of binders, attractants and preservatives commonly used in aquafeeds is given in Table 20. The use of feed attractants may not be essential for Nile tilapia, although these are often used in commercial feed formulations. Fishmeal is often recommended as a feeding stimulant in tilapia diet. Moreover, dimethyl-β-propiothetin and several organic acids are reported to have feeding stimulatory effects. The composition of practical least-cost vitamin and mineral premixes commonly used for commercial tilapia feeds is shown in Tables 21 and Table 22, respectively. At present, due to lack of data, the contribution of endogenous vitamins and minerals present in the feed ingredients used (or that present in natural food in the pond) are not taken into consideration when adding these premixes into tilapia feeds. However, with more research on the availability of essential nutrients (Wang et al., 2006) the inclusion levels of several vitamins in commercial tilapia feeds may be reduced. In the provinces of Guangdong, Fujian, Guangxi and Hainan in China, tilapia are stocked at 30 000-37 500 fish/ha and fed with pelleted feed (28-35 percent CP) two to three times daily at 6-10 percent body weight (BW)/day for fish <100g, 3-6 percent BW/day for fish 100-250 g and 1.5-4 percent BW/day for fish 300-800 g (Lai and Yi, 2004). Under these conditions yields range from 15-20 tonnes/ha at a feed conversion ratio of 1.5-2.0. It is generally known that smaller fish consume more feed per unit body weight compared to larger fish. Recommended feeding schedules for different sized tilapia with expected growth rates as provided by a feed manufacturer is presented in Table 23. Recommended feeding tables for tilapia using formulated feed under different stocking densities in semi-intensive (pond only) and intensive farming systems (cages, tanks and ponds) are presented in Tables 24 and 25, respectively. The suggested feeding schedules as shown in Table 26 are widely used for semi-intensive and intensive culture in freshwater ponds in China (Table 29a) (Miao and Liang (2007) and in intensive culture of tilapia in ponds and cages in many Southeast Asian countries (Table 29b) (Orachunwong et al., 2001). It should be noted that tilapia consume less feed during the colder months of the year in countries where there are substantial seasonal temperature fluctuations. Many ingredients absorb water, which leads to pellets becoming unstable in water. For instance, wheat and rice bran severely reduce the water stability while cereal by-products act as binders (particularly when gelatinization occurs). Most oilseed by-products allow for good water stability and animal by-products are rather poor binders. If the compounded feed is heat treated then 20 percent of the feed should be made up of ingredients with a high starch content (corn, wheat, etc.) in order to improve water stability through gelatinization. |
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