3. NUTRIENT SOURCES - COMPOSITION OF FEEDSTUFFS AND FERTILIZERS (cont.)

3.8 Single cell proteins

Single cell protein (SCP) is a term applied to a wide range of unicellular and filamentous algae, fungi and bacteria which can be produced by controlled fermentation processes for use as animal feed. Compared with conventional plant and animal feed proteins these micro-organisms offer numerous advantages as protein producers:

• Their production can be based on raw carbon substrates which are available in large quantities (ie. coal, petro-chemicals, natural gas) or on agricultural or cellulosic waste products which would otherwise cause an environmental hazard.

• The majority of micro-organisms cultured are highly proteinaceous (40–80% crude protein on a dry weight basis, depending on species).

• They have a very short generation time; under optimum culture conditions bacteria can double their cell mass within 0.5–2h, yeasts within 1–3h, and algae within a 3–6h period.

• They can be cultivated in a limited land space and produced continuously with good control independently of climate.

• To a certain extent their nutritional composition can be controlled by genetic manipulation.

In addition to the use of monocultures of SCP for protein production, there is also the possibility of using mixed SCP cultures such as activated sludges (ie. mixed suspension of bacteria, algae and unicellular animals) resulting from the biological oxidation of specific waste streams such as brewery waste, human sewage, and paper processing waste.

In general these microbial products are good sources of dietary protein, with methionine generally being the first limiting essential amino acid within algae, yeast and activated sludges, and lysine within bacterial SCP (Schultz and Oslage, 1976). In contrast to conventional plant and animal feeding stuffs a significant proportion of the nitrogen contained within SCP is present in the form of high-polymer nucleic acids and their decomposition products. For example, Kihlberg (1972) reported total nucleic acid values of 5–12% for yeasts and 8–16% by weight for bacteria, as a percentage of the dry matter. The value of these non amino acid N-containing substances in the nutrition of monogastric animals, including fish and shrimp, appears to be minimal (Tacon and Jackson, 1985). In general SCP are poor sources of dietary lipid and calcium, but are an excellent source of dietary vitamins (ie. B-vitamins, inositol and choline within yeast SCP; Tacon, 1987) and are good sources of dietary phosphorus. For a review of the composition and nutritive value of SCP see Schultz and Oslage (1976).

The average proximate and essential amino acid composition of SCP is shown in Table 21 and 22 respectively.

¹ The data presented represents the mean values from various sources, including: Allen (1984); Appler and Jauncey (1983);Bath et.al., (1984); Cooley (1976); Gohl (1981); Imada et.al., (1979); Janssen (1985); Kaushik and Luquet (1980); Ling (1967);Matty and Smith (1978); Murray and Marchant (1986); NRC (1983); Orme and Lemm (1973); Parsons, Stephens & Strickland(1961);Schultz & Oslage (1976); Smith and Palmer (1976); Smith et.al., (1975); Soeder (1981); Tacon and Ferns (1979); Tacon et.al.,(1983); Verkataraman, Becker and Shamala (1977); Windell, Armstrong and Clineball (1974); Yoshida and Hoshii (1980);Zimmerman and Tegbe (1977).

² W-Yeast is bakers yeast which has been grown in a culture medium supplemented with fish oil or cuttle fish liver oil(Imada et.al., 1979).

³ Mixed fungal culture of Hansenula anomala, Candida Kruzei and Geotrichum candidum (Murray and Marchant, 1986).

⁴ Data as presented by Ling (1967).

⁵ Data only available on a dry matter basis (Parsons, Stephens and Strickland, 1961).

¹ The data presented represents the mean values from various sources, including: Allen (1984); Bolton and Blair (1977);Cooley (1976); D'Mello, Peers and Whittemore (1976); FAO (1970); Kaushik and Luquet (1980); Murray and Marchant (1986);NRC (1983); Orme and Lemm (1973); Smith and Palmer (1976); Smith et.al., (1975); Soeder (1981); Windell, Armstrong andClineball (1974); Tacon (1979); Zimmerman and Tegbe (1977).

² Mixture of H. anomala, C. kruzei and G. candidum (Murr and Marchant, 1986).

3.9 Invertebrate food organisms

In numerous aquaculture systems live zooplankton (ie. rotifers, copepods, brine shrimp nauplii) are commonly used as live food organisms for the mass propagation of many marine and freshwater fish and shrimp larvae. These live foods are generally produced at high densities, in specialized units, separated from the fish or shrimp culture tanks. Although the nutritive value of zooplankton for fish or shrimp will depend on the physical size, strain, source and developmental status of the animal in question, the proximate, mineral and amino acid composition of individual species is relatively constant. By contrast, the fatty composition within individual species has been found to vary considerably, depending on strain, the developmental status of the animal, and the culture method used for its production. In fact, it is generally believed that the essential fatty acid profile (EFA) of living zooplankton and phytoplankton feeds is the principal factor governing their success (or not) as feed for larval fish and shrimp; zooplankton containing a high proportion of the essential polyunsaturated fatty acids (ie. w6:fatty acids - 18:2w6 and 20:4w6 or w3 fatty acids-20:5w3 and 22:6w3) possessing the highest nutritional value for freshwater or marine larval fish/shrimp species respectively. Live zooplankton is a good source of dietary protein (although the protein is often deficient in sulphur amino acids), lipid, minerals, vitamins and carotenoid pigments. For a review of the chemical composition and nutritive value of zooplankton see Watanabe, Kitajima and Fujita (1983) and Simpson, Klein-MacPhee and Beck (1983).

In addition to the common use of live zooplankton as complete larval feeds, considerable interest has also been focussed on the use of selected macro-invertebrates animals, either alive or in their processed or byproduct form, as feed for fish and shrimp. In particular, emphasis has been centred on the use of those insect larvae and oligochaete worms which have the ability of utilizing waste streams (ie. animal manures, domestic sewage, agricultural wastes) which would otherwise have little or no direct feed value within a compounded animal diet. By virtue of their ability to utilize and upgrade waste nutrients into a ‘palatable’ nutrient rich package, these macro-invertebrate food organisms constitute a potentially valuable source of dietary nutrients for farmed fish and shrimp. For a review of the chemical composition and nutritive value of selected macro-invertebrate food organisms see Yurkowski and Tabachek (1978), Gohl (1981), Ling (1967) and Stafford (1984).

The average proximate and amino acid composition of selected invertebrate food organisms is shown in Table 23, and 24 respectively. In view of the direct effect of the culture medium and diet on the fatty acid composition of zooplankton, the fatty acid composition of these live food organisms will be dealt with under larval feeds within part III of this training manual series.

¹ The data presented represents the mean values from various sources, including: Allen (1984); Choubert and Luquet (1983);Cresswell and Kompiang (1981); Deshimaru and Shigeno (1972); Deshimaru et.al., (1985); Elmslie (1982); Gallagher andBrown (1975); Gohl (1981); Hilton (1983); Imada et.al., (1979); Ling (1967); Mathias et.al., (1982); Meyers (1986, 1987);Newton et.al., (1977); NRC (1983); Seidel et.al., (1980); Simpson, Klein-MacPhee and Beck (1983); Stafford and Tacon(1984, 1985); Tacon (1986a); Tacon, Stafford and Edwards (1983); Watanabe, Kitajima and Fujita (1983); Yoshida andHoshii (1978) and Yurkowski and Tabachek (1978), Leger et.al., (1986).

² Data obtained from Watanabe, Kitajima and Fujita (1983).

³ Data obtained from Leger et.al., (1986); no information provided on moisture, crude fibre or NFE content-the carbohydratecontent being represented by a single value.

⁴ Data compiled from Watanabe, Kitajima and Fujita (1983) and Yurkowski and Tabachek (1978).

⁵ Data obtained from Meyers (1986); crude protein (N×6.25) values do not correspond to the corrected true protein valueof 53.5% and 22.8% for shrimp heads and shrimp hulls respectively (ie. values corrected for chitin content)

⁶ Data obtained from Newton et.al., (1977); no value is presented in this table for NFE, as the existing values reportedby these authors total 106.4%.

¹ The data presented represents the mean values from various sources, including: Allen (1984); Cresswell and Kompiang (1981); Deshimaru and Shigeno (1972); Deshimaru et.al., (1985); Gallagher and Brown (1975); Hilton (1983); Mathias et.al.,(1982); Meyers (1986); Newton et.al., (1977); NRC (1983); Seidel et.al., (1980); Stafford (1984); Tacon, Staffordand Edwards (1983); and Watanabe, Kitajima and Fujita (1983).

² Mean of the eight amino acid analyses presented by Watanabe, Kitajima and Fujita (1983).

³ Origin of meal not specified (Deshimaru and Shigeno, 1972).

⁴ Tacon, A.G.J. (unpublished data).

3.10 Vertebrate animal by-products

Almost all slaughterhouse, poultry, fish and milk by-products can be considered for use within aquaculture feeds. With the exception of specific products such as blood meal and hydrolysed feather meal (which despite a high crude protein content have specific amino acid imbalances), the majority of animal by-products have a well balanced essential amino acid profile (thus complementing the lysine and methionine deficiences of plant based feeding stuffs) and are good dietary sources of protein, lipid, energy, minerals and vitamins. For a review of the nutritive value and processing techniques used for the preparation of individual animal by-products see Barlow and Windsor (1984), Gohl (1981) and Mann (1962).

The average proximate, amino acid and fatty acid composition of the major animal by-product feeds used within aquaculture feeding strategies is shown in Table 25, 26 and 27 respectively.

¹ The data presented represents the mean values from various sources, including: Allen (1984); Barlow and Windsor(1984); Bath et.al., (L984): Bolton and Blair (1977); Cooley (1976); Davies, Rumsey & Nickum (1976); Gohl (1981);Hastings (1974); Jackson, Kerr and Cowey (1984); Ling (1967); Lovell (1979); McDonald, Edwards and Greenhalgh (1977);NRC (1982, 1983); Reece et.al., (1975); Rumsey et.al., (1981); Tacon (1982); Tacon (1986); Tacon, Webster & Martinez(1984); Tatterson and Windsor (1974); Wee, Kerdchuen and Edwards (1987); Wilson, Freeman and Poe (1984) and Wood,Capper and Nicolaides (1985).

² Dairy processing wastes, including the processing of cheeses; carbohydrate content expressed as 34.1% lactose(Rumsey et.al., 1981)

³ Due to the wide variation in proximate composition of fish (depending on species, time of year, growth, nutritionalhistory, and spawning period, etc), the 5 categories of Gohl (1981) are presented; Group A - oysters and clams;Group B - Carp, cod, flounder, haddock, hake, mullet, oceanperch, pollack, rockfish, whiting, crab, scallop andshrimp; Group C - Halibut and tuna; Group D - Anchovy, herring, mackerel, salmon, sardine; and Group E - Siscowetlake trout (Cristivomer namacush)

⁴ Catfish processing wastes includes head, skin and viscera: mean water content of waste reported as 67% (Lovell, 1979).

⁵ Includes various marine species such as Gadidae/Lophiidae/Rajidae, which have a white flesh and low lipid content.

⁶ Mean of various freshwater fish species as reported by Allen (1984).

⁷ Condensed fish solubles is a product (press liquor) resulting from the pressing of fish during the fish mealmanufacturing process (Barlow and Windsor, 1984).

⁸ Fish protein concentrate is the product arising from the solvent extraction of fish meal.

⁹ Acid preserved silages are produced by the external addition of mineral or organic acids to the macerated whole fishor wet fish by-product.

¹⁰ Composition presented is for a high lipid sprat silage, after a 2-week storage period at 20°C with added ethoxyquinantioxidant (Jackson, Kerr and Cowey, 1984).

¹¹ Composition presented is for a 6-month old silage (18°–22°C storage temperature; Wood, Capper and Nicolaides, 1985).

¹² Fish silage produced by lactic acid bacterial fermentation in the presence of a suitable carbohydrate substrate.

¹ Data presented represents the mean values from various sources, including: Allen (1984); Barlow and Windsor (1984);Bolton and Blair (1977); FAO (1970); Jackson, Kerr and Cowey (1984); NRC (1982/1983); Tacon (1982); Wilson, Freemanand Poe (1984); Wood, Capper and Nicolaides (1985).

² Values for fresh fish obtained from FAO (1970).

³ Composition presented is for a silage after a 8-week storage period at 20°C with added ethoxyquin: Authors reporta 54.5% loss in tryptophan from an initial concentration of 0.55% after a 8-week storage period; Methionine andCystine reported as total sulphur amino acids (Jackson, Kerr and Cowey, 1984).

⁴ Composition presented is for a silage after a 6-month storage period at 18–22°C; values are expressed as % of totalrecovered amino acids (Wood, Capper and Nicolaides, 1985).

¹ Data represents the mean values from various sources, including: Austreng, Skrede and Eldegard (1979); Barlow and Windsor (1984);Castell (1978); Deshimaru, Kuroki and YoneÅ (1982, 1982a); Kanazawa et.al, (1979, 1979a); Takeuchi and Watanabe (1978); Takeuchi,Watanabe and Ogino (1978, 1979); Thomas and Paulicka (1976); Watanabe and Takeuchi (1976); Stickney and Wurts (1986).

² Mean fatty acid content of the whole body lipids of four freshwater fish species (Sheeps herd, Tullibee, Maria and Alewife; Castell, 1978).

³ Mean fatty acid content of lipids extracted from manufactured fish meals (Barbow and Windsor, 1984).

3.11 Mineral supplements

Table 28 summarises the elemental composition of the major salts commonly used as dietary mineral mixtures within complete diets for fish and shrimp.

¹ Adapted from Bolton and Blair (1977); for detailed information on thecomposition of mineral supplements see NRC (1982).

3.12 Chemical fertilizers

Table 29 summarises the elemental composition of the major chemical fertilizers commonly used for increasing the natural productivity of water bodies.

¹ Values expressed as a percent of the pure salt.

² Liming materials differ in their ability to neutralize acid; the neutralizingvalue of the pure salts of CaCO₃, CaMg(CO₃)₂ and CaO being 100%, 109%, 136%, and179% respectively (Boyd, 1979).

³ Super phosphate is a mixture of Ca(H₂PO₄)₂ and CaSO₄ (gypsum) and is produced bytreating fluoroapatite ((Ca₃(PO₄)₂)₃.CaF₂) with sulphuric acid (H₂SO₄) as follows:(Ca₃(PO₄)₂)₃.CaF₂ + 7H₂SO₄ → 2Ca(H₂PO₄)₂ + 7CaSO₄ + 2HFSuperphosphate has a P₂O₅ equivalence of 16–20%, 85% of which is water soluble(Boyd, 1979).

⁴ Triple superphosphate is a more concentrated form of Ca(H₂PO₄)₂ and is producedby treating fluoroapatite with phosphoric acid (H₃PO₄) as follows:(Ca₃(PO₄)₂)₃.CaF₂ + 14H₃PO₄ → 10Ca(H₂PO₄)₂ + 2HFTriple superphosphate has a P₂O₅ equivalence of 44–54%, 85% of which is watersoluble (Boyd, 1979).

3.13 Organic manures

Organic manures include all plant and animal materials which in their fresh, decomposed or dried form can be used as fertilizers to enhance the production of natural live food organisms within an enclosed water body containing fish or shrimp; the increased production of live food organisms (ie. phyto-zooplankton, algae, bacteria, plants, micro and macro-invertebrates) inturn serving as a direct source of dietary nutrients for the farmed fish or shrimp. The most commonly used organic manures include fresh or dried livestock manure (ie. farm animal faeces, with or without urine), fresh or dried plant residues (ie. straw, husks, leaves, vegetable waste, grass cuttings, tree by-products, seaweed), farmyard manure (ie. mixture of animal faeces and urine with crop residues, usually straw or sawdust, and occasionallysoil), compost (ie. partially decomposed mixture of animal and/or vegetable materials), and human waste (ie. nightsoil, sewage and sewage effluents).

The fertilizer value of an organic manure will depend primarily upon its carbon (C), nitrogen (N), phosphorus (P) and potassium (K) content, and its consequent susceptibility to bacterial degradation within the water body. For example, the C:N ratio of the applied manure will determine its rate of bacterial decomposition and hence the time lag between application and increased pond productivity; manures with a low C:N ratio (<50; animal faeces/urine/green weeds/grass) being more rapidly decomposed by bacteria than manures with a high C:N ratio (>100; straw, sugar cane bagass, sawdust). Table 30 summarises the average composition of the major organic manures used within aquaculture systems. For a more indepth review of the nutritive value of organic manures see Misra and Heese (1982) and Müller (1980).

¹ Adapted from Misra and Heese (1982)

² Mean moisture content of the fresh faeces of bffalo, cattle, sheep, horse, pig,poultry and humans is approximately 81%, 83%, 65%, 78%, 75%, 73% and 80%respectively.

³ Data from Bressani et.al., (1975).

⁴ Nitrogen figure reported is low:average nitrogen content of dried leafy grassis c. 4%.

⁵ Gotaas (1956) reports C/N ratio and nitrogen content of dried seaweed as 19 and1.9% respectively.

⁶ Gotass (1956) reports C/N ratio and nitrogen content of dried farmyard manureas 14 and 2.15% respectively.

⁷ Data from Little (1979).

⁸ Data from Gotaas (1956)