Proteins and amino acids
Proteins (muscles, enzymes and hormones) are central to feed formulation systems (FAO, 2003) as an expensive component of feeds (Shiau, 1998). Penaeus indicus protein requirements as given in various reports are 43 percent (Colvin, 1976a), 35 percent and 42.9 percent (Ahamad Ali, 1982), 32.3 percent (Ahamad Ali, 1996), 30 to 43 percent (Alagarswamy and Ahamad Ali, 2000) and 35 to 37.5 percent (Gopal and Paul Raj, 1990) (Table 2a).

Dietary lipids are a highly digestible and concentrated source of energy that supplies 8 to 9 kcal/g, about double of that supplied by either carbohydrate or protein (Mead et al., 1986; Chuang, 1990). Energy requirements reported for P. indicus at 350 to 400 kcal/100 g (Alagarswamy and Ahamad Ali, 2000) are higher than for species like Penaeus monodon (223 to 371 kcal/100 g, Chuntapa et al., 1999).

A dietary source of cholesterol is essential (Whitney, 1970; Kanazawa et al., 1971; New, 1976) for optimal survival and growth (Coutteau et al., 2002). In crustaceans, cholesterol is nutritionally superior to other sterols (Teshima, 1997). Raw material ingredients such as fish, shrimp, squid and crab meals contain cholesterol and can provide a portion of the requirement for cholesterol in shrimp feeds (Table 2c). The cholesterol levels recommended for P. indicus range from 0.2 to 0.5 percent (Table 2a) (Ahamad Ali, 2001).

Most aquatic animals have an optimal dietary carbohydrate range of 20 to 40 percent (Andrews, Sick and Baptist, 1972; Sick and Andrews, 1973; Cuzon, Guillaume and Cahu, 1994). In general, shrimp utilize complex starches like cornstarch better than glucose (Shiau and Peng, 1992). Standard wheat starch is generally the starch source used in shrimp feeds (Cruz–Suarez et al., 1994; Cuzon et al., 2000). Carbohydrates reduce (“spare”) the use of protein, allowing a lower optimal protein level (Bautista, 1986; Shiau and Peng, 1992). Advised carbohydrate levels in P. indicus feeds are given in Tables 2a and 12.

Fish and shrimp feeds can be produced with 12 to 13 percent moisture (Table 12), but to contend with free water migration problems to the sealed edges of feed bags causing spoilage, feed producers have opted for lower levels ranging from 9 to 10 percent (Goh, 2005) (Table 5). This ensures pellet stability and quality during storage, but also adds drying costs and losses caused by “shrinkage”.

The addition of shell waste, chitin or glucosamine to shrimp feeds is beneficial to growth (Conklin, 1989). Dietary chitin, supplemented at 5 percent, enhanced growth (Shiau and Yu, 1998), while fermented prawn shell waste was beneficial to the growth of Penaeus indicus (Amar, Philip and Bright Singh, 2006).

Crude fibre is practically indigestible for crustaceans (Hertrampf, 2006). 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. Crude fibre levels in commercial feed should be less than 4.0 percent (Hertrampf, 2006) (Tables 4, 5 and 12).

The “ash content” is a measure of the total amount of minerals present within a food and should be minimized (Tables 4 and 12). The “mineral content” reflects specific elements in the diet. 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, 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) (Table 9).

Phosphorus is the most expensive mineral supplement in aquatic feeds (Fox et al., 2006). As dietary inclusion levels increase, utilization is usually reduced and unconsumed phosphorus leads to nutrient loading of culture systems and aquaculture effluents. When substituting fishmeal with soybean or other plant meals, poor availability of phosphorus from feed grains is a problem. A high percentage of the phosphorus in feed grains is bound to phytic acid. Phytate is an antinutritional factor, as it reduces mineral and amino acid availability in feeds (Fox et al., 2006).

Ahamad Ali (2001) advised a Ca:P ratio for P. indicus of 1:1.98, with Ca at 0.53 percent and P at 1.05 percent of the diet (Table 12). This is in agreement with research on other species showing that Ca should be minimized to improve phosphorus availability and that phosphorus is a necessary dietary supplement (Chuang, 1990; Davis and Lawrence, 1997; Penaflorida, 1999; Fox et al., 2006 (P. monodon postlarvae); Deshimaru et al., 1978; Deshimaru and Yone, 1978 (P. japonicus); Cheng et al., 2006 (Penaeus vannamei).

Ca can likely be absorbed from the seawater (Deshimaru et al., 1978), so supplementation may not be necessary (Davis and Lawrence, 1997). Different phosphate sources have different availabilities. Calcium levels in excess of 2.3 percent should be avoided (Davis and Lawrence, 1997).

Davis, Lawrence and Gatlin (1992a) found that the individual deletion of Mg, Mn, Fe, Zn and Cu from the mineral premix resulted in reduced tissue levels of these minerals in P. vannamei. Seawater likely contains sufficient sodium and chloride to satisfy the physiological needs of shrimp (Davis and Lawrence, 1997), but potassium (Shiau and Hsieh, 2001), zinc (Davis, Lawrence and Gatlin, 1993b) copper (Davis, Lawrence and Gatlin, 1993a; Lee and Shiau, 2002), iodine (Davis and Lawrence, 1997) and manganese (Davis, Lawrence and Gatlin, 1992a; Fa–Yi and Lawrence, 1997) are needed as supplements in the diet.  Iron supplementation to commercial shrimp feeds is not necessarily needed (Davis, Lawrence and Gatlin, 1992b; Davis and Lawrence, 1997). A lack of magnesium causes decreased growth, poor survival and reduced feed efficiency in shrimp (Piedad-Pascual, 1989b), but oceanic seawater has high magnesium levels (1 350 mg/l), and plant ingredients are high in magnesium so shrimp may not require a supplemental dietary source of magnesium (Davis and Lawrence, 1997). A dietary requirement for selenium is likely. However, with its potentially toxic effects, the level should be less than 0.3 mg/kg (Davis and Lawrence, 1997).

Vitamin C is essential in shrimp diets for good growth and survival. When using stable forms of vitamin C such as ascorbyl polyphosphate, doses of 100 to 500 ppm are sufficient for maximal survival and growth (Guillaume, 2001). 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 to 500 g/tonne feed (mg/kg feed) requires 715 to 1 430 g/tonne.

Although not widely discussed, paraaminobenzoic acid is included in some research and commercial vitamin mixes (e.g. Shiau and Su, 2004 and Rotosquare Enterprises Ltd Taiwan) (Table 8).

Penaeids, as all animals, are unable to synthesize carotenoids de novo (Goodwin, 1984). Astaxanthin is the predominant carotenoid in penaeids (Katayama, Katama and Chichester, 1972; Tanaka et al., 1976; Okada, Nur–E–Borhan and Yamaguchi, 1994). β-Carotene, echinenone and canthaxanthin are other pigments found in  shrimp (Meyers and Latscha, 1997). Astaxanthin improves colouration, enhances biological functions and improves survival, growth and stress resistance in penaeid shrimp (Pan and Chien, 2004). Natural carotenoids such as dried Spirulina and carotenoid extracted from Dunaliella are potentially cheaper than synthetic products such as astaxanthin and beta–carotene (Supamattaya et al., 2005). Carotenoids from other products include astaxanthin from yeast, marigold meal, paprika and Haematococcus algae (Hunter and Chamberlain, 2006). Haematococcus has about 1.5 to 3.0 percent astaxanthin by dry weight (Todd Lorenz and Cysewski, 2000). A “finisher diet” should include 50 to 100 mg/kg of astaxanthin (Meyers and Latscha, 1997) (Table 12).

Apparent crude protein digestibility (ACPD) for shrimp is high (over 80 percent), but more research is required (Lee and Lawrence, 1997). Digestibility data are therefore not easily applied to practical feed formulations at present (Table 14). The general flow of energy for growth and other activities is illustrated in Figure 17.