Nutrient requirements of common carp were fairly well researched and established (Table 4.1, Table 4.2, Table 4.3 and Table 4.4).
Protein requirements
The daily requirement of common carp for protein is about 1 g/kg body weight for maintenance and 12 g/kg body weight for maximum protein retention. The efficiency of nitrogen utilization for growth is highest with a protein intake of 7 to 8 g/kg body weight/day. Crude protein levels ranging from 30 to 38 percent appear to satisfy the fish optimally. This level has been determined by using semi-purified diets containing a single high-quality protein source (casein, whole-egg protein or fishmeal). When the diet contains sufficient digestible energy, the optimal protein level can be effectively kept at 30–35 percent (Watanabe, 1982).
The quantitative requirement for amino acids has been determined by several studies and is shown in Table 4.1.There are some minor differences in the requirement for individual amino acids, depending on the growth stage. The lysine requirement at the fingerling stage is 2.25 percent of the diet (6 percent protein) and decreases to 1.75 percent (5.4 percent) at the fingerling stage, whereas the methionine requirement does not change. As has been recognized in other fish species, cystine and tyrosine can spare or replace certain portions of dietary methionine and phenylalanine, respectively (Takeuchi, Satoh and Kiron, 2002). It remains questionable whether carp requires dietary taurine supplements. Ogino (1980) reported that the amino acid requirements could be estimated from data on the amino acid profile of the whole-body and daily body protein deposition.
Data shown in Table 4.2 are based on the assumption that fish consuming a diet containing 35 percent protein with 80 percent protein digestibility and fed daily at a level of 3 percent of the body weight deposits 0.58 g of protein per 100 g of body weight daily. However, in this approximation of deposition rate, metabolic pathways of amino acids that do not lead to protein synthesis are not accounted. The absorption of individual amino acids differs greatly, depending on the protein source and time after feeding (Dabrowski, 1983, 1986). Although the absorption rate is a useful tool for describing metabolic amino acid requirements, further studies are needed in this area.
Dietary lipids requirements
As an omnivorous fish, common carp can effectively utilize both lipids and carbohydrates as dietary energy sources. The enrichment of the digestible energy content from 13 to 15 MJ/kg diet by addition of lipid at levels of 5–15 percent to diets did not result in higher growth rate or improved net protein utilization (Takeuchi, Watanabe and Ogino, 1979a). Increasing dietary lipid seems to increase its body deposition. From the essential fatty acids, common carp requires both n-6 and n-3 fatty acids. Supply of 1 percent of each of these fatty acids leads to best growth and feed efficiency in juvenile common carp (Takeuchi and Watanabe, 1977). Phospholipids (PL) have numerous roles in larval feeding, so they have to be supplied when common carp larvae are fed on artificial diets instead of PL-rich live food. Radunzneto, Corraze and Charlon (1994) found that during the first two weeks, dietary PL supply seemed to be more critical for early larval survival and growth than a supply of n-3 fatty acids from cod liver oil.
Dietary carbohydrate requirements
Studies on carbohydrate utilization in common carp have shown that the amylase activity in the digestive tract and the digestibility of starch in fish are generally lower than those of terrestrial animals. Common carp, being omnivorous, has an intestinal activity of amylase that is higher than in carnivorous fish. It was found that the ratio of intestinal length to body length in carp is 1.8–2, i.e. four times greater than that of rainbow trout (Oncorhynchus mykiss) and Japanese eel (Anguilla japonica). This accounts for the better utilization of carbohydrates by common carp. Murai, Akiyama and Nose (1983) investigated the effects of various dietary carbohydrates and the frequency of feeding on feed utilization of common carp. While the starch diet produced the highest weight gain and feed efficiency at two daily feedings, glucose and maltose were as efficiently utilized as starch when fed at least four times daily. This indicates that there is a drop in the absorption efficiency of glucose and maltose when large amounts are fed at a time. Other investigators found that common carp used carbohydrate effectively as an energy source. Later, Takeuchi, Watanabe and Ogino (1979b) also confirmed the dietary value of carbohydrates. The optimum range of dietary carbohydrate may be considered to be 30–40 percent for common carp, as proved by many studies in this field.
Vitamin requirements
The qualitative and quantitative vitamin requirements of carp are also well investigated (Table 4.3). The dietary requirements for folic acid and vitamins B12, D and K have not been determined, but it is supposed that some of these vitamins can be synthesized by the intestinal microflora in common carp, as in other freshwater fish (Lovell and Limsuwan, 1982; Hepher, 1988). The vitamin requirements of common carp are affected by various factors, such as size of fish, water temperature and diet composition. For example, fingerling or adult common carp do not require vitamin C because they can synthesize ascorbic acid from D-glucose. The vitamin E requirement may increase corresponding to the level of polyunsaturated fatty acids in the diet. As extrusion techniques to make floating feeds become more popular, it seems certain that vitamins may be destroyed during feed manufacture and storage. Hence, the supplemental levels of vitamins in fish diets are always two to five times higher than the requirement levels.
Mineral requirements
Mineral requirements are summarized in Table 4.3. Common carp requires cobalt, copper, iron, magnesium, manganese, phosphorus and zinc. Since common carp lacks an acid-secreting stomach essential for digesting and solubilizing various compounds containing both calcium and phosphorus, the availability of phosphorus depends on the water solubility. Phosphorus from tricalcium phosphate or fishmeal (FM) is less available than that from the more soluble mono- and dicalcium phosphates. Supplementation of monobasic phosphate to FM-based diets resulted in an increase in growth response of common carp (Takeuchi, Satoh and Kiron, 2002).
It was also found that exogenous supply of copper, manganese, magnesium and zinc is necessary for carp diets. Tricalcium phosphate may inhibit the availability of trace elements, such as zinc and manganese, although to a much lesser extent than in rainbow trout (Satoh et al., 1989). Dabrowska, Meyer-Burgdorff and Gunther (1991) found a significant interaction between magnesium supply and protein level of feed when feeding young carp with diets containing graded levels of magnesium and protein. A magnesium level of 0.6 g/kg was required to elevate plasma and bone magnesium content and to reduce clinical signs of hypercalcinosis, but a further increase of dietary magnesium up to 3.2 g/kg did not affect fish growth. In magnesium-deficient fish, a considerable amount of magnesium was absorbed via extra-oral routes; however, this way of meeting the need for magnesium is inadequate in fast-growing fish. These non-oral routes of mineral uptake may be important, especially in pond conditions. In a study on the interaction between zinc deficiency and lipid intake, Taneja and Arya (1994) observed that the malabsorption of nutrients was linked to the deposition of lipid in the intestine.
Energy requirements
The energy requirements of carp are much less investigated than other aspects of nutrition. As described in other teleosts, both fasting metabolic rates and maintenance energy requirements are affected by water temperature. The resting metabolic rates at temperatures below 17 °C are quite low. A linear relationship between nitrogen (N) intake and heat increment in feeding was also proposed, with a value of around 40 kJ/g N intake (Chakraborti, Ross and Ross, 1992; Kaushik, 1995).
Protein and lipid requirements are related to digestible energy. The optimum range of the digestible energy/protein ratio for maximum growth was 97–116 when based on the measured digestible energy (Takeuchi, Watanabe and Ogino, 1979b). Ohta and Watanabe (1996) provided a dietary energy budget for carp fed a practical diet comprised of 25 percent FM, 4 percent meat meal, 10 percent soybean meal and 8 percent maize-gluten meal as the main protein sources. Gross energy intake (100 percent) was partitioned as follows (Ohta and Watanabe, 1996):
- 29.9 percent lost as faecal energy;
- 1.5 percent as non-faecal energy;
- 31.9 percent as heat increment; and
- 36. 7 percent as net energy (including 12.6 percent for maintenance and activity and 24.1 percent as productive energy).
It was also reported in the same study that the digestible energy requirements for maximum growth were 285, 548 and 721 kJ/kg body weight/day (at feeding rates of 1.83, 3.60 and 5.17 percent of body weight/day, respectively).
