Introduction
Nutrient can be defined as a chemical substance necessary for life and growth, absorbed in the body or tissue through metabolic processes. In a world where nearly 30% of the total population is suffering from malnutrition and over 70% of the planet is covered with water, aquatic foods represent an essential component of the global food basket to improve the nutrition, health, and wellbeing of all peoples. Currently 800 million people around the world suffer from acute malnourishment, and by 2050 the global population will rise from 7. 3 billion to 9. 7 billion (FAO 2014). Thus, there is a huge challenge of filling the global food basket and aquaculture can be an alternative to feed the rapidly expanding population. Aquaculture is probably the fastest-growing food-producing sector and now accounts for almost 50 percent of the world’s fish that is used for food.. Fisheries and aquaculture may contribute significantly to food security and adequate nutrition for the ever increasing population in the present scenario of climate change.
Fish is one of the most-traded food commodities worldwide with more than half of fish exports by value originating in developing countries. It has lot of potential and can therefore be expected to provide relief from malnutrition especially in Asian countries (Ashraf et al. 2011). A portion of 150 g of fish can provide about 50-60 percent of an adult’s daily protein requirements (FAO) 2014). The role of nutrition is one of the most important factors for fish production as it plays a key role in the aquaculture industry.
Understanding feed, feeding and nutrition of fish species suitable for fishery and aquaculture development is one of essential preconditions for successful aquaculture production. Recently, intensification in fish farming has reached to such an extent that the technology is based, to a large extent, on high protein pelleted diets that are usually energy intensive, involving higher degree of management practices as well as higher capital investments (Islam 2002). Proper nutrition is one of the most important factors influencing the ability of cultured organism to attain the genetic potential for growth, reproduction and longevity (De Silva and Anderson 1995), and its status is considered as one of the important factors that determine the ability of fish to resist diseases. If the feed is not consumed by the fish or if the fish are unable to utilize the feed because of some nutrient deficiency, then there will be no growth. An undernourished animal cannot maintain its health and be productive, regardless of the quality of its environment (Bureau and Cho 1999). The role of artificial feed in intensive fish farming cannot be ignored as nutritional requirements of fish depend upon the feed supplied (Srivastava et al. 2013). The quantity and quality of feed consumed have an impactful effect on growth, feed conversion and proximate composition of fish (Jena et al. 1998).
The commercial viability of fish culture depends on market demand and cost of production. The largest fraction of the production cost (40-70%) lies in the fish feed (Ogbe et al. 2004; Otubusin et al. 2007, Daniel, 2017). Therefore, formulation of cost-effective feeds can significantly influence the profitability. One of the challenges is to develop less wasteful, cost-effective feeds and development of such feeds is dependent on knowing a species nutritional requirements and meeting those requirements with balanced feed formulations and appropriate feeding practices (Gatlin III 2010). Any balanced formula for fish diet should include essential amino acids, energy source, essential fatty acids, specific vitamins and minerals to support life and promote growth.
Protein requirements
Protein is one of the most important and expensive components of fish feed, required to build and repair damaged tissues. Its inadequacies affect growth performance and general body maintenance. Knowledge of the protein requirement of fish is essential to formulate well balanced, low cost and environmentally friendly feeds (Luo et al. 2007; Zehra and Khan 2012; Kpogue et al. 2013). Thus, it is important to formulate feeds that meet, but do not exceed protein requirements for maximum growth, while minimizing feed costs and water pollution (Sa et al. 2006). The information on protein nutrition of cultivable fish species has been documented and listed in Table 1.
Table 1. Protein requirements of Cultivable fish species
Fish species | Protein requirement | Size range | Feeding level | Reference |
Channa micropeltes | 52 | rower | 2%bw/d | Wee and Tacon (1982) |
Channa murulias | 54 | Fry | 8-5%bw/d | Raizada et al. 2012 |
Channa punctatus | 45 | Fingerling | App satiation | Zehra and Khan 2012 |
Channa striata | 55 | Fry | 10%bw/d | Mohanty and Samantaray 1996 |
55 | Fry | | Kumar et al. 2010 |
Clarias batrachus | 30 | Fry | 10%bw/d | Chuapoehuk 1987 |
40 | Adult | | Khan and Jafri 1990 |
Heteropneustes fossilis | 35 | Fry | | Akand et al. 1989 |
43 | Young | App satiation | Siddique and Khan 2009 |
Labeo, catla | 30 | Fingerling | 5%bw/d | Renukaradhya & Varghese 1986 |
Labeo fimbriatus | 30. 14 | Fingerling | App satiation | Jena et al. 2012 |
Labeo rohita | 25 | Yearling | App satiation | Khan et al. 2005 |
35 | Fingerling | 5%bw/d | Debnath et al. 2012 |
25 | Fingerling | Ad. lib. | Sarkar et al. 2015 |
Amino acids requirements:
Referring to protein requirements is nevertheless usual in fish nutrition as protein includes both indispensable amino acids and dispensable amino acids that provide the undifferentiated nitrogen required for the synthesis of nitrogenous compounds of physiological interest (Oliva-Teles 2012). The requirements of amino acids have been worked out quantitatively and qualitatively.
a. Qualitative amino acid requirements:
The qualitative amino acid requirements of fishes have usually been based upon growth and feed efficiency in long-term feeding studies in which one of several amino acids is removed from a well-defined formulated diet. Significant reduction in weight gain occurs in fish fed the selected amino acid-deficient diets compared with growth of fish fed the control diet. Thereafter, any group of fish fed a diet determined to be deficient in an amino acid, as indicated by reduced growth and feed efficiency, is separated into two subgroups: One subgroup is retained on the amino acid-deficient diet (control diet minus one amino acid), whereas the other subgroup is fed the control diet. Reduced growth rate or cessation of growth in fish fed the amino acid-deficient test diet versus the control diet is considered to be confirmation of a dietary requirement for the specific amino acid being tested. The first successful amino acid test diet for fish was developed by Halver (1957). He developed his initial test diet based on previous amino acid test diets used in determining the amino acid requirements of young albino rats. Halver (1957) compared test diets containing 70% crystalline L-amino acids formulation based on the amino acid patterns of whole chicken egg protein, chinook salmon egg protein, and chinook yolk sac fry protein. The test diet based on whole chicken egg protein gave the best growth and feed efficiency for chinook salmon for a 12-week period. Therefore, this test diet was used to determine the qualitative amino acid needs of Chinook salmon (Halver et al., 1957). These workers determined the essentiality of the 18 common protein amino acids by comparing the relative growth rates of chinook salmon fed the basal and the specific amino acid-deficient diets over a 10-week period. The results indicated that the following 10 amino acids were indispensable for chinook salmon: arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. All other species that have been studied to date have been shown to require the same 10 amino acids.
b. Quantitative amino acid requirements:
From a quantitative point of view, efficiency of protein utilization and muscle protein growth are the most critical issues. Optimizing the amino acid supply in tune with the requirements and improving protein utilization for body protein growth with limited impacts on the environment in terms of nutrient loads is a generic imperative in all aquaculture production system (Kaushik and Seiliez 2010). Amino acids and their metabolites are important regulators of key metabolic pathways that are necessary for maintenance, growth, feed intake, nutrient utilization, immunity, behavior, larval metamorphosis, reproduction as well as resistance to environmental stressors and pathogenic organisms in various fishes (Li et al. 2009). Dietary am...