Why wheat flour or wheat maida is used in fish feed formulation?
Answers
Explanation:
Indian white prawn - Feed formulation
Algae as a live food
Shrimp larvae are found naturally as a part of the zooplankton, beginning as herbivores but soon becoming omnivores with a preference for zooplankton. Live feeds are commonly used in shrimp larval rearing to postlarval stage. Algae are readily consumed from Zoea 1 until Postlarvae 2 (Evans, 1992) (Figure 21).
Figure 21. Mass algal culture from test tubes of pure strains (courtesy of Laurence Evans)
Formulated feed – feed ingredients
Together with the nutrient requirements of shrimp, it is imperative to know the proximate composition of feedstuffs to be able to formulate a diet to meet these needs. The moisture content, crude protein, crude lipid, crude fibre, nitrogen-free extract (digestible carbohydrates), ash content, vitamins and minerals, available phosphorus, amino acid content and levels of polyunsaturated fatty acids of the n–3 and n–6 series should be known for each feed ingredient (Piedad–Pascual, 1989a). Plant proteins can be deficient in key amino acids when compared with fishmeal (Table 15) (Ahamad Ali, Syama Dayal and Ambasankar, 2004).
A variety of plant and animal feedstuffs is used in shrimp feeds (Table 13a, Table 13b). A combination of feed ingredients is needed to supply the nutrients and energy shrimp need for best growth. The percentage inclusion of each feed ingredient is determined by factors such as feedstuff proximate composition, amino acid profile, shrimp nutrient requirements, ingredient cost, availability of each ingredient, feed digestibility and processing characteristics.
The major components of a typical 35 percent protein shrimp diet are wheat flour (35 percent), soybean meal (20 percent) and fishmeal (25 percent) (Hunter and Chamberlain, 2006) and perhaps yeast. These ingredients provide the protein, amino acids and energy in the diet. Protein supplements are sourced from animal, yeast or plant proteins. Raw materials that have proven to be excellent major protein sources for shrimp diets include squid, soybean meal, shrimp meal, fishmeal, krill and scallop waste (New, 1976; Venero, Davis and Lim, 2008).
Fishmeal
Marine shrimp aquafeed diets included 35 percent fishmeal content in 1995, 25 percent in 2000 (Tacon, 1998) and approximately 25 percent in 2007 (Venero, Davis and Lim, 2008). Commercial shrimp diets typically contain approximately 25 percent fishmeal (Tacon and Barg, 1998), and there is a trend towards lower inclusion levels. Fishmeal is a rich source of high quality protein, has relatively high-energy content and is rich in important minerals such as phosphorus, B vitamins and essential fatty acids.
The shrimp feed industry mainly uses high quality (premium grade: prime or super prime) fishmeal imported from Chile or Peru (FAO, 2007b). Rancidity from lipid oxidation, which may occur during storage, is one of several factors affecting fishmeal (Laohabanjong et al., 2009). Ricque–Marie et al. (1998) found that fresh fishmeal gave better growth in all shrimp species tested.
Fish oil
Fish oils and squid oils provide essential fatty acids required by shrimp (FAO, 2007b). Fish oil inclusion averaged 3 percent of the diet in 1995 and 2 percent in 2000.
Wheat
This ingredient is used as a binder in pelleted shrimp and prawn feeds (FAO, 2007b) and a carbohydrate source. Pelleted feeds require a minimum of 20 percent starch from cereal grains to improve water stability (Chamberlain and Bortone, 2006). Ideally, wheat should have high gluten content. A low wet gluten index (23 to 28 percent) relative to the ideal index for shrimp feed pelleting (32 percent to 35 percent) (Suresh, 2007) would require wheat gluten or other binders to achieve the necessary pellet water stability.
Soybean meal
Soybean meal has one of the best essential amino acid profiles of all protein-rich plant feedstuffs (Fox, 2008a). Soybean meal with hulls (44 percent crude protein) and dehulled soybean meal (48 percent crude protein) are available in large quantities. These products are used in shrimp and prawn feeds (FAO, 2007b). Marine shrimp appear to be able to digest soybean meal very efficiently.