Thursday, July 14, 2016

Nutritional requirements of Penaeus monodon

Natural production
Natural production in a pond provides cultured shrimp with a portion of their food (energy and nutrients), especially in extensive aquaculture, while with increased stocking densities, supplemental feeds become increasingly important (Tacon, 2002). Fertilization increases the number of nematodes, copepods and polychaetes in ponds, and these are all actively grazed upon by shrimp (FAO, 1984). A strong correlation has been found between bacterial numbers and the developing meiofauna (FAO, 1984). Focken et al. (1998) looked at the contribution of food, plants, crustaceans and detritus in the diet of shrimp in a semi-intensive pond and found commercial feed to comprise less than half the total feed intake.

Complete feeds
A complete feed is a feed formulated to provide all required nutrients in the proper proportions necessary for rapid weight gain and high feed efficiency to produce healthy shrimp of high quality. Feed cost is about half of variable production costs in shrimp culture (Lim and Akiyama, 1995). The objective of commercial shrimp nutrition is to maximize the growth rate as cheaply as possible while producing a healthy shrimp of high product quality.

Proteins and amino acids
Protein is the key building block for feed formulation systems (FAO, 2003) and a major and expensive component of feeds (Shiau, 1998). Approximately 73 percent of the dry matter of Penaeus monodon is crude protein (Sarac et al., 1994). The protein requirements for P. monodon as given in various reports are: 45.8 percent (Lee, 1971), 40 percent (AQUACOP, 1977; Khannapa, 1977; Alava and Lim, 1983), 35 to 40 percent (Lin et al., 1981), 36 to 40 percent (Shiau and Chou, 1991), greater than 35 percent (McVey, 1993) and 35 percent (Bages and Sloane, 1981; Syama Dayal et al., 2003). 

Shrimp require 10 essential amino acids (EAA): arginine, methionine, valine, threonine, isoleucine, leucine, lysine, histidine, phenylalanine and tryptophan (Cowey and Forster, 1971; Shewbart, Mies and Ludwig, 1973; New, 1976; Coloso and Cruz, 1980; Kanazawa and Teshima, 1981; Piedad-Pascual and Kanazawa, 1986; Lim and Akiyama, 1995; Lovell, 2002; Fox et al., 2006) (refer to Tables 2a and 12a). Methionine, lysine and arginine are generally the first limiting amino acids when applying least-cost optimization (formulation) of commercial shrimp feed formulae (Fox et al., 2006). Of the nonessential amino acids, cystine has a sparing effect for methionine and tyrosine for phenylalanine (Fox et al., 2006). 

Kanazawa (1989) found that shrimp larvae showed good growth and high survival rates when the amino acid profile of the diet simulated that of the body protein of larval prawn. Deshimaru and Shigeno (1972) also advised that shrimp feeds should contain a similar amino acid profile to that of the shrimp species, as protein nutritive value is based on its amino acid composition (Wilson and Poe, 1985).

Lipids (fats, oils)
Lipids (triacylglycerols) form a component of cell membranes and energy reserves, so are important nutrients for shrimp. The dietary lipids required by penaeids can be categorized into classes of neutral lipids (including essential fatty acids), sterols and phospholipids (D'Abramo, 1989) and carotenoids (Kumaraguru Vasagam, Ramesh and Balasubramanian, 2006).

Nutritional studies on shrimp lipids have shown that shrimp require essential fatty acids (EFA) for their normal growth (Liao and Liu, 1989). Shrimp can synthesize some fatty acids de novo from acetate (D’Abramo, 1997). Four fatty acids are considered essential for Penaeus monodon: linoleic (18:2n–6, LOA), linolenic (18:3n–3, LNA), eicosapentaenoic (20:5n–3, EPA) and docosahexaenoic (22:6n–3, DHA) acids (Kanazawa et al., 1979a; Kanazawa, 1984; D'Abramo 1997; Catacutan, 1991; Merican and Shim, 1996; Glencross and Smith, 2001a; Glencross et al., 2002a). The two n–3 highly unsaturated fatty acids (HUFA) are the most important. Glencross et al. (2002c) showed that for weight gain, the optimal total lipid level at a dietary protein level of 47.3 percent is between 4.5 and 7.5 percent. Growth of shrimp is superior when diets contain lipids (oils) of marine rather than vegetable origin (Guary et al., 1976; Kanazawa, Teshima and Tokiwa, 1977). The 20C and 22C n–3 HUFA found in marine oils have a higher nutritive value (growth promoting effect) than the 18C PUFA (Kanazawa, 1984; D’Abramo, 1989; Xu et al., 1993). However, the presence of either of the linoleic (18:2n–6, LOA) and linolenic (18:3n–3, LNA) fatty acids in the diet further enhances the growth potential of P. monodon (Merican and Shim, 1996; Glencross et al., 2002b).

[Note: The terminology such as ”n–3” and “w3” is short notation for “omega-3” fatty acids and both will be used in this document. Polyunsaturated fatty acids (PUFAS) have two or more unsaturated bonds. Highly unsaturated fatty acids (HUFAS) have a chain of 20 or more carbon atoms and more than three unsaturated bonds (D’Abramo, 1997).]

Chuntapa et al. (1999) found that shrimp fed with a feed containing 35 percent protein, an energy content of 330 kcal/100 g, and a lipid:carbohydrate ratio of 1:4.6 had highest growth and survival rates. Other fatty acids such as arachidonic acid (ARA, 20:4n–6) may not promote growth (Merican and Shim, 1996) in juvenile P. monodon, but may still may be required for effective maturation (Glencross and Smith, 2001b). Arachidonic acid also enhances shrimp survival (Xuet al., 1993), and elevated levels of this fatty acid are found naturally in wild animals (O'Leary and Matthews, 1990).

The ratio of the dietary n–3 and n–6 fatty acids is considered important to fatty acid metabolism and lipid nutrition in shrimp species (Xu et al., 1993). Millamena (1989) found that the reproductive performance of P. monodon was best when the fatty acid profile had a high n–3/n–6 ratio, resembling the fatty acid profile of the wild P. monodon maturing ovary. An optimal ratio of n–3 to n–6 fatty acids is about 2.5 to 1 (Glencross et al., 2002b). Fatty acid inclusion in feeds can be found in Tables 2a and 12a.

As essential fatty acids are required in the diets of shrimp, their content in the diet should be considered when replacing fishmeal and oil with other substitutes. Alternatives such as algal oil can be used as suitable fish oil substitute (HUFA source) (Patanaik et al., 2006).

Dietary lipids are a highly digestible and concentrated source of energy that supplies 8–9 kcal/g, about double of that supplied by either carbohydrate or protein (Mead et al., 1986; Chuang, 1990). Chuntapa et al. (1999) found that for shrimp fed a diet with 33–44 percent protein, an energy content of 223–371 kcal/100 g provided the best growth rate. The optimal protein:energy (P:E) ratios for optimal growth and survival of juvenile tiger shrimp were 150 and 146 mg protein/kcal, respectively. AQUACOP (1977) found that 330 kcal/100 g was required for optimal growth of P. monodon. Similarly, Shiau and Chou (1991) found that weight gain, feed conversion ratio (FCR) and protein gain of P. monodon improved up to a dietary energy of 330 kcal/100 g for a 36 percent protein diet and of 320 kcal/100 g for a 40 percent protein diet. Bautista (1986) also found best growth at 330 kcal/100 g with a 40 percent protein diet. Bautista (1986) and Shiau and Peng (1992) established a P:E ratio of 125 mg protein/kcal (29.86 mg protein/kJ). Hajra, Ghosh and Mandal, 1988) estimated the optimal dietary P/E ratio for P. monodon to be 28 mg protein/kJ (117.2 mg protein/kcal).

Cholesterol is a necessary constituent of cell membranes and a precursor for steroid hormones. Shrimp cannot synthesize sterols, so a dietary source is essential (Whitney, 1970; Kanazawa et al., 1971; New, 1976) and cholesterol is nutritionally superior to other sterols (Teshima, 1997). Cholesterol is the most expensive single ingredient for use in shrimp feeds (Coutteau et al., 2003). In general, supplementation with purified cholesterol or other cholesterol-containing ingredients is needed to obtain optimum survival and growth (Coutteau et al., 2003). Castille et al. (2004) found that the dietary requirement for cholesterol ofPenaeus vannamei was 0.15 percent. Dietary requirements for P. monodon range from 0.17 to 1 percent (Wu, 1983, 1986; Chen, 1993; Sheen, et al., 1994; Paibulkichakul et al., 1998; Smith, Tabrett and Barclay, 2001). Penaeus monodon fed a sterol-free diet had poor growth and survival (Sheen et al., 1994). D’Abramo et al. (1985) and Teshima and Kanazawa (1983) have shown that digestion and assimilation of dietary cholesterol is affected by dietary lipids and phospholipids. Raw materials such as fish, shrimp, squid and crab contain cholesterol and provide some of the requirement for cholesterol in shrimp feeds.

Phospholipids (lecithin) have a growth-promoting effect in shrimp (Kanazawa et al., 1979b; Kontara, Coutteau and Sorgeloos, 1997; Glencross, 1998; Gong et al., 2001; González-Félix and Perez-Velazquez, 2002). Today, soya beans are the most commercially important source of lecithin (Hertrampf, 1991) and are commonly used in shrimp diets. Kumaraguru Vasagam, Ramesh and Balasubramanian (2006) concluded that dietary SL (standard fluid soy lecithin (63 percent phospholipid)) at 2 percent of the diet improves lipid digestibility and growth performance of juvenile P. monodon with vegetable oils as their lipid source.

The use of soybean lecithin as a phospholipid source has the added benefit of adding choline and inositol to the diets. 1.0 kg/tonne of deoiled lecithin (powder form) adds 36 mg choline and 38 mg inositol per kg of feed. At a 1.5 percent lecithin fortification in the diet, 570 g/tonne of inositol and 540 g/tonne of choline are provided (Hertrampf, 1991). Akiyama, Dominy and Lawrence (1991) advised the supplementation of choline at 400 mg/kg feed and inositol at 300 mg/kg feed.

Cuzon et al. (2000) found that the digestibility of carbohydrates in shrimp varied according to flour type, botanical origin of starch and inclusion level. Native starch was digested as well as pre-cooked starch. Best results were attained with standard wheat starch, and this is commonly the main starch source in shrimp feeds.

Raw materials high in crude fibre create grinding problems and reduce the binding capacity and water stability of the pellets. The pellet water durability (stability) should last for at least two hours when the feed is immersed in water. Commercial diets should therefore have as low as possible crude fibre levels and should not exceed 4.0 percent (Hertrampf, 2006).

Ash and minerals
The “ash content” is a measure of the total amount of minerals present within a food, whereas the “mineral content” is a measure of the amount of specific inorganic components present within a food, such as Ca, Na, K and Cl. Shrimp can assimilate some of their minerals directly from the water. The mineral requirements of shrimp have not been fully established (Guillaume, 2001). Shrimp can absorb calcium and phosphorus from the seawater. Macronutrients for shrimp nutrition are Ca, P, Mg, K, Cl, S and Na, while the micronutrients are Fe, Zn, Cu, Mn, Ni, Co, Mo, Se, Cr, I, Fl, Sn, Si, Va and As (CIBA, 2002). Seven minerals (calcium, copper, magnesium, phosphorus, potassium, selenium and zinc) have been recommended for inclusion in penaeid shrimp diets (Davis and Gatlin, 1996) 

Fifteen vitamins may be required by shrimp, including the water–soluble vitamins thiamin, riboflavin, niacin, vitamin B6, pantothenate, folate, vitamin B12, biotin, choline, myoinositol (inositol) and vitamin C (ascorbic acid) and the fat–soluble vitamins A, D, E and K (Conklin, 1989). Penaeus monodon diets deficient in ascorbic acid, biotin, folic acid, niacin, thiamine and alpha–tocopherol resulted in poor appetite and poorer feed conversion efficiency. Diets lacking a specific vitamin resulted in histopathological changes in the digestive gland cells of P. monodon (Reddy, Ganapathi Naik and Annappaswamy, 1999). Over-fortification of some vitamins (e.g. riboflavin, niacin and vitamin B6) can result in reduced shrimp growth (Deshimaru and Kuroki, 1979; Catacutan and De la Cruz, 1989; Conklin, 1997).

Moss, Forster and Tacon (2006) found that pond water has a sparing effect on vitamins in shrimp diets. Microbes likely contributed significantly to this effect. Microbes associated with detritus in the ponds can substantially reduce vitamin levels required in shrimp feeds, resulting in reduced feed costs without compromising shrimp growth, survival or FCR.

L–Ascorbyl–2–Polyphosphate (AsPP) is available commercially as ROVIMIX® STAY–C® 35. This product has 35 percent ascorbic acid activity, so the recommended vitamin supplementation (inclusion) at 250–500 g/tonne feed (mg/kg feed) requires 715–1 430 g/tonne of polyphosphorylated L–ascorbic acid.

Astaxanthin and carotenoids
Penaeids, as all animals, are unable to synthesize carotenoids de novo (Goodwin, 1984). Astaxanthin is the predominant carotenoid in penaeids (Katayama, Kamata and Chichester, 1972; Tanaka et al., 1976; Okada, Nur-E-Borhan and Yamaguchi, 1994), accounting for 86 to 96 percent of total carotenoids in the exoskeleton of P. monodon (Okada, Nur-E-Borhan and Yamaguchi, 1994). Natural carotenoids such as dried Spirulina and carotenoid extracted fromDunaliella improved colouration in shrimp and are potentially cheaper than synthetic products such as astaxanthin and beta–carotene (Supamattaya et al., 2005). To ensure a good colour at harvest, the finisher diet should include 50–100 ppm (mg/kg) of astaxanthin (Meyers and Latscha, 1997; Pan and Chien, 2004).

Apparent crude protein digestibility (ACPD) for shrimp is high (over 80 percent). More research is required on the ACPD and metabolizable energy (ME) of shrimp (Lee and Lawrence, 1997). Digestibility data are therefore not easily applied to practical feed formulations at present. Feeds are never fully digestible.

Shiau, Lin and Chiou (1992) found that soybean meal digestibility as both dry matter digestibility and protein digestibility was affected by salinity. They also found individual amino acids to be fairly well digested. Sudaryono, Tsvetnenko and Evans (1996) studied the apparent dry matter digestibility (ADMD) and apparent protein digestibility (APD) of marine animal protein sources prepared from fisheries by-products and concluded that fisheries by-products were digested as efficiently as those prepared from commercial fishmeals, while plant protein sources with lupinseed meal lead to a decrease in the digestibility with P. monodon. In general, plant protein sources were less well utilized (Allan, 1998).

Not much research has been done on the digestible energy of raw materials. Digestible energy (kcal/g) can be roughly calculated based on protein at 5 kcal/g, fat at 9 kcal/g and N-free extract at 4 kcal/g (Shiau, Kwok and Chou, 1991). The maintenance requirement of P. monodon for protein and energy was 0.007 g digestible crude protein and 0.3 KJ digestible energy/g body weight/d, respectively (Allan, 1998).


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