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2.3 Manufacture and storage of complete pelleted diets

2.3.1 Background

Feed manufacturing is concerned with the physical transformation of a written formulation into a compounded “edible” diet. A wide variety of techniques exist for the manufacture of complete aquaculture feeds; ranging from straight mixing/blending (dry feed mash, hand compacted semi-moist/moist feed mash, ball, paste, or cake: New, 1987), flaking (flaked dry larval diets: Meyers and Hagood, 1984), dravo processing (non-compacted semi-moist or dry feed crumble or pellet; Pigott, 1980), wet compaction pelleting (semi-moist or moist pellets: AQUACOP, 1978; New, 1987), dry or steam compaction pelleting (dry pellets: Csavas, Majoros and Varadi, 1979; Robinson, 1976; Hastings and Higgs, 1980, New, 1987), extrusion/expansion pelleting (dry, moist or rehydratable expanded pellets: Smith, 1976; Williams, 1986; Melcion et al., 1983; Hilton, Cho and Slinger, 1981; Vens-Cappell, 1984; Werner & Pfleiderer, Struttgart, Federal Republic of Germany - Processing sales literature: extrusion cooking for improved shrimp feeds), to microencapsulation (dry and rehydratable microencapsulated larval diets: Nixon, 1976; Jones and Gabbot, 1976; Chow, 1980; Meyer, Butler and Sirine, 1971; Jones, 1984; Scura, Fischer and Yunker, 1984). The choice of manufacturing process to be employed will depend on the feeding habit of the fish or shrimp to be fed (ie. benthic, pelagic or surface feeder; visual or olfactory feeder; moist or dry diet feeder; rapid or slow feeder) and its physical feed requirements (ie. feed size, bouyancy, texture, palatability, and desired water stability) for all stages of the culture cycle. These technical factors will inturn have to be balanced against the market value of the cultured species and the availability of cash funds, feed ingredients and services. It is not the intention here to mechanically describe each of the above mentioned feed manufacturing processes (the techniques are well established and readers requiring this information should consult the individual review papers mentioned above; for a general review see ADCP, 1980 and New, 1987), but rather to focus on some of the problems which are unique to the manufacture of complete pelleted aquaculture diets.

2.3.2 Grinding

The efficiency of a feed manufacturing process and the biological efficacy of a compounded diet will depend upon the initial grinding, and consequent particle size, of the basic raw feed materials used. The advantage of grinding are two fold; to the nutritionist it facilitates the destruction of the heat labile anti-nutritional factors invariably present and it improves nutrient digestibility by increasing the surface area of the feed particles; to the animal feed compounder grinding improves feed acceptability and pelletability (it prolongs die life, facilitate the penetration of steam within the feed particles, and increases the horsepower efficiency), it improves the mixing property of individual feed ingredients, and also increases the bulk density of the feed stuff (Tacon and Jackson, 1985). However, in contrast to the intensive poultry and livestock feed manufacturing industry, where incoming ingredient sources are seldom ground to a particle size below 1mm, the manufacture of good quality pelleted aquaculture feed necessitate that all feed ingredients be first ground so as to pass through a 0.25mm sieve (for premixes and starter crumbles) and a 0.35mm sieve (for grower and broodstock pellets) so as to meet the physical size requirement of the animal farmed and for maximum nutritional benefit to be gained from the nutrients present. Furthermore, for the early larval growth phase of many marine fish and shrimp species, the preparation of microencapsulated or microparticulate larval diets necessitate the use of very finely ground ingredient sources forthe production of complete rations which may range in size from 10 to 500μm (Kanazawa et. al., 1982a). In fact, one of the major problems encountered with the manufacture of pelleted aquaculture feeds within developing countries is that aquaculture feeds are invariably produced within feed mills specifically designed and geared for the manufacture of poultry and livestock feeds, and as such do not have the necessary capacity for fine grinding nor the material through - put to justify the purchase of such equipment. Needless to say the cost of fine grinding, both in terms of equipment procurement and energy consumption, is high (for review see Hastings and Higgs, 1980; New, 1987, and Pfost, 1976).

2.3.3 Pelleting

Steam compaction pelleting is by far the commonest production technique employed for the commercial manufacture of aquaculture feeds (for review see Hastings and Higgs, 1980; Csavas, Majoras and Varadi, 1979; Robinson, 1976; and New, 1987). However, apart from the generally recognised benefits ascribed to conventional dry or steam compaction pelleting (Figure 2; Heinemans, 1986), the recent development and application of extrusion (ie. expansion) pelleting techniques 1 has offered some new horizons for the aquaculture feed compounder. The advantages of the extrusion pelleting over conventional steam pelleting can be summarized as follows:

1 Extrusion or expansion pelleting is a moist heat process whereby the preground and blended dry feed ingredients are first conditioned with steam and/or water under atmospheric pressure (feed mixture at this stage will contain 20–30% moisture; conditioning temperature 65–95°C) and then conveyed to a pressurised extrusion barrel (known as an extruder) where the feed mixture is then cooked to a temperature of 130–180№C by means of heat and mechanical shear for 10–60 seconds (cooking period and temperature depending on the particle size of the feed ingredients, the composition of the feed mash, and the physical property of the extruded diet required). The cooked meal is then extruded via a tapering screw through a die plate at the end of the pressurised extrusion barrel to the exterior where it then expands and is cut into the desired length or physical form. During this process the extrusion cooked feed emerges from the die with a lower bulk density and having a moisture content of 25–30%, which then requires further drying. The extrusion process requires a certain amount of carbohydrate (as starch) to be present; starch on gelatinizing becomes plastic, absorbs water and on superheating vapourises with consequent expansion. A typical flowsheet for a feedmill utilizing a extrusion-cooking system is shown in Figure 3.

Figure 2

Figure 2. Advantages of pelleting (Source: California Pellet Mill-Pelleting Handbook - no date given)

Figure 3

Figure 3. Typical flow sheet for a animal feed manufacturing plant utilizing a extrusion-cooking system (Source: Horn, 1979; Williams, 1986)

However, on the negative side it should be pointed out that extrusion pelleting is more expensive than regular steam pelleting (both in terms of equipment procurement and operating energy costs, including the added cost of drying the extruded feed) and may result in the loss or damage of heat-sensitive nutrients (ie. such as ascorbic acid, thiamine, poly-unsaturated fatty acids and lysine) if cooking is not correctly controlled (Melcion et. al., 1983; Hilton, Cho and Slinger, 1981; Hilton and Slinger, 1983; Slinger, Razzaque and Cho, 1979; Vens-Cappell, 1984; Horn, 1979). Rather than over fortifying the feed mash before extrusion cooking, heat sensitive additives (ie. marine lipids, vitamins, antioxidants, emulsifiers, and pigments) may be sprayed onto expanded pellets after extrusion (Hastings and Higgs, 1980). Further-more, in view of the high carbohydrate requirement (c. 15-25% diet) for adequate extrusion cooking, care should be taken when fixing dietary carbohydrate levels within formulations intended for carnivorous fish or shrimp species which have a low dietary tolerance for digestible carbohydrate (Hilton, Cho and Slinger, 1981; Hilton and Slinger, 1983). Example formulations of extruded rations are shown in Table 5 (formulation no 6 and 11).

2.3.4 Storage

The manufacture of an aquaculture diet inevitably entails a storage period for the finished ration within the factory warehouse or farm store prior to feeding. Since feed rations are composed of perishable nutrients, it follows that this storage period should be kept to a minimum and that adequate storage conditions are provided so as to prevent deteriorative changes occuring in nutrient composition through oxidative damage and/or through microbial, insect or rodent infestation. The deleterious effect of prolonged storage on the stability of dietary vitamins and lipids has been discussed previously (Tacon, 1987; Section 3.7.4 and 5.5.1), and so reference here will only be made concerning the relationship between environmental storage conditions and pest infestation.

The most important environmental factors governing the storage or shelf life of a manufactured feed are ambient temperature and humidity; these factors dictating the rate at which chemical changes take place, the increase in moisture content of the stored product, and the growth of contaminating pests such as fungi, bacteria, and insects within the feed. For example, Figures 4/5 and Table 6 show the relationship between ambient temperature and relative humidity on pest/fungal infestation and feed moisture content within stored animal feedstuffs, respectively. By far the greatest pest hazard within hot and humid climates is the microbial infestation of stored feeds with filamentous fungi or moulds; moulds normally only being active at relative humidities above 70%, and activity generally being greatest at temperatures of 35–40°C (Cockerell, Francis and Halliday, 1971). By constrast, bacterial infestation only generally occurs within stored feeds posessing a moisture content in excess of 25% (equivalent to a relative humidity above 90%). The most common fungi involved in the spoilage of feedstuffs include Aspergillus, Cladosporium, Penicillium and Helminthosporioum (Figure 5). The detrimental consequences of mould growth within stored feeds can be summarised as follows:

Table 6. Effect of storage relative humidity on feed moisture

Feed rationRelative humidity (%)
 Feed moisture (%)
Pig starter8.113.419.3
Swine grower10.214.616.9
Cattle ration8.113.717.7
Urea cattle supplement8.913.617.6
Dehydrated alfalfa6.812.016.3

Source: Jones (1987)

Figure 4

Figure 4. Relationship between ambient temperature and feed moisture content on the risk of pest infestation within stored feedstuffs (Source: Zuercher, 1987)

Figure 5

Figure 5. Temperature and relative humidities at which species of fungi commonly found on stored feed materials may be most important: a - Aspergillus candidus; b - A. flavus; c - A. fumigatus; d - A. tamarii; e - A. niger; f - A. glaucus; g - A. terreus; h - Penicillium cyclopium; i - P. martensii; j - Cladosporium spp; k - Sporendonema sebi (Source: Cockerell, Francis and Halliday, 1971)

The basic requirements for a good feed storage structure is that it should provide protection against high temperatures, humidity, moisture, insects and rodents. A common fault in the design of storage buildings is to neglect to provide for an adequately constructed floor. This, like the walls, should be effectively damp-proofed, and bags containing feeds should always be stored on wooden pallets. Ideally, moist/semi-moist aquaculture rations should be stored under refrigeration or used on the same day of preparation to avoid vitamin losses (Tacon, 1987; section 5.5.1). Similarly, dry pelleted feeds should be stored under clean dry ventilated conditions, avoiding high temperatures and direct sunlight, and used within two months of manufacture. In practice, however, feed storage periods will range from as little as a few hours to as long as six months, depending upon the availability of feeds, the minimum feed order of the factory, the size of the fish or shrimp farm, and the financial status of the farmer. For a review of the chemical preservatives which can be used within feed rations to combat mould growth and oxidative damage see Table 5 (formulations No. 4, 5, 10, 11, 17 and 19) and Tacon (1987a; section 4.1). Guidelines for good feed storage are given by Chow (1980a) and New (1987).

2.4 Feeding practices

2.4.1 Feeding of marine fish and shrimp larvae1

In this review emphasis will be placed on the complete diet larval feeding methods currently employed for the mass propagation of marine fish and shrimp species; the majority of whom have small bouyant eggs (< 1.5mm diameter) with poor yolk sac reserves, and on hatching produce vulnerable and small planktonic larvae (0.3 - <5mm body length: Blaxter, 1969). The feeding of freshwater fish larvae (which tend to be larger in size than their marine or brackishwater counterparts) will not be dealt with here, as these species are usually produced using semi-intensive pond nursery feeding methods.

According to Kuronuma and Fukusho (1984) the principles guiding the feeding of larvae in tanks or enclosures, are:

On the basis of the above criteria, four larval or ‘hatchery’ feeding strategies are currently available for the mass propagation of marine fish and shrimp larvae, through metamorphosis, to the post-larval or fry stage. These include:

1 Larvae refers to the period between hatchling (yolk sac individuals) and the fish fry or shrimp post-larval stage (when the individual has completed metamorphosis and takes on the appearance of a subadult).

At present almost all commercial marine shrimp and fish hatchery operations rely on the exclusive use of a succession of live food organisms or zooplankton, and in particular the rotifer Brachionus plicatilis (size range: 100–400um, wet weight c. 0.003mg) and the brine shrimp Artemia salina (newly hatched nauplii size range: 420–520um, wet weight 0.01–0.03mg, dry weight 1.6–3.3ug; hydrated decapsulated cyst size range: 200–270um), for the larval culture cycle. The mass production and nutritive value of live food organisms will not be discussed here, as this aspect will be covered in a separate manual (‘La Produccion de Alimento Vivo y su Importancia en Acuacultura’, Torrentera Blanco and Tacon; in preparation). Table 7 summarises the live food feeding regimes currently employed for the mass propagation of the major cultured marine fish and shrimp species. Despite the economic efficacy of a well managed shrimp or marine fish hatchery using a live food feeding regime, there are a number of disadvantages associated with an intensive live food hatchery feeding strategy (Tacon, 1986), including:

Table 7. Live food feeding regimes for marine fish and shrimp larvae

Species:RED DRUM (Sciaenops ocellatus)
Egg diameter 0.9–1.0mm
Standard length at hatching 1.7–1.8mm
Metamorphosis completion 28–42 days from hatching at 25°C
Source of feeding example cited: Holt, Arnold and Riley (1987) Temperature: 25–30°C Salinity: 25–30 parts/thousand (ppt) Larval density: 10–20/1 for Ist 10 days, 1–2/1 next 14 days, 0.5/1 next 14 days. Survival: 5–10% after 30 days. Fish length at metamorphosis is about 25mm.
Further reading: Anon (1986), Chamberlain, Miget & Haby (1987), Roberts, Morey, Henderson & Halscott (1978), Holt (1987) and Henderson-Arzapalo (1987).

Species:EUROPEAN SEA BASS (Dicentrarchus labrax)
Egg diameter 1.1–1.3mm
Standard length at hatching 3.5–4.0mm
Wet weight on hatching 0.25–0.45mg
Metamorphosis completion 50–60 days from hatching at 20°C
Source of feeding example cited: Freddi (1985) Temperature: 20°C Salinity: 35ppt Larval density: egg incubation 50–70/1 (hatching 90%, viability 95%) Survival: 15–20% at end of metamorphosis (c. day 60) from egg incubation stage. Fish weight on metamorphosis is about 50mg.
Further reading: Barnabe (1986), Girin (1979), Kentouri (1980), Johnson & Katavic (1984), Ravagnan (1984), Gatesoupe & Luquet (1981), Gatesoupe & Robin (1982), Lumare (1978), Johnson & Katavic (1986), Katavic (1986), Hadj Kacem, Aldrin & Romestand (1986).

Species:GILTHEAD BREAM (Sparus aurata)
Egg diameter 0.9–1.0mm
Standard length at hatching 2.0–2.5mm
Wet weight on hatching 0.2–0.3mg
Metamorphosis completion 50–60 days from hatching at 23°C
Source of feeding example cited: Freddi (1985) Temperature: 23°C Salinity: 35ppt incubation/day 10–60, 25ppt hatching to day 10. Larval density: egg incubation 50–70/1 (hatching 90% viability 80%). Survival: 10–15% at end of metamorphosis from egg incubation.
Further reading: Person-Le Ruyet & Verillaud (1980), Barnabe (1986), Freddi, Berg & Bilio (1981), Lumare (1978), Kentouri, Divanach & Paris (1981), Tandler & Helps (1985).

Species:TURBOT (Scophthalmus maximus)
Egg diameter 0.9–1.2mm
Standard length at hatching 2.1–2.8mm
Wet weight on hatching 0.1–0.3mg
Metamorphosis completion 30–40 days from hatching at 15–18°C
Source of feeding example cited: Person-Le Ruyet (1986) Temperature: 18–20°C. Salinity: 20–34ppt. Larval density: 20–40/1 to day 20–25, thereafter 5/1. Survival 0–40% at end of metamorphosis. Fish weight after one month about 50–70mg.
Further reading: Bromley & Howell (1983), Gatesoupe (1982), Person-Le Ruyet et. al., (1983), Kuhlman, Quantz & Witt (1981). For composition of weaning diets see Gatesoupe (1982) and Person-Le Ruyet et. al., (1983). Lumare (1978).

Species:SOLE (Solea solea/S. vulgaris)
Egg diameter 1 – 1.6mm
Standard length at hatching 2.5–3.8mm
Wet weight on hatching 0.4–0.6mg
Metamorphosis completion 15 days from hatching (17–19°C)
Source of feeding example cited: Person-Le Ruyet (1986) Temperature 18–20°C. Salinity 20–34ppt. Larval density 50–80/1, after metamorphosis 2–10,000/m2. Survival 60–80% at one month. Weight after one month is about 50–75mg. Normal weaning period 25–30 days after hatching; period can be reduced to 10–15 days by using semi-moist crumb diet (Gatesoupe, 1983)*
Further reading: Cadena Roa et. al., (1982); Fuchs (1982), Gatesoupe (1983), Metailler, Menu & Moriniere (1981), Dendrinos et. al., (1984), Lumare (1978), Girin & Person-Le Ruyet (1977), Metailler et. al., (1983), Lumare (1978).
* Used larval densities of 15–28/1. Feed size 315um from day 10, 650um at day 17, feed given continuously during the day.

Species:GREY MULLET (Mugil cephalus)
Egg diameter 0.8–1.0mm
Standard length at hatching 2.2–3.5mm
Wet weight on hatching 0.2–0.3mg
metamorphosis completion 40–50 days from hatching at 20–22°C
Source of feeding example cited: Nash & Konongsberger (1981) Temperature 20–22°C. Salinity 32–35ppt, reducing to 30ppt by day 7 and 20ppt by day 30. Larval density no more than 6/1 at start, with anticipated density at day 21 of 0.33/1. Survival 5% of original number of eggs after 50-day culture cycle.
Further reading: Liao (1975), Kuo & Nash (1975), Nash, Kuo & McConnell (1974), Lumare (1978), Nash & Shehadeh (1980), Cataudella et. al., (1988).

Species:RABBITFISH (Siganus guttatus)
Mean egg diameter 0.45–0.6mm
Standard length at hatching 2mm
Metamorphosis completion 24–35 days from hatching at 26–32°C
Source of feeding example cited: Juario et. al., (1985) Temperature 26–30°C. Salinity 34ppt. Larval density 5–125/1. Larval survival 0.7–24.7% (day 35)
Further reading: * Artificial diet - Lim, Sukhawongs & Pascual (1979) Bryan & Madraisau (1977), May, Popper & McVey (1974), Popper, May & Lichatowich (1976), Akatsu, El-Zahr & Al-Aradi (1983)

Species:BROWN-SPOTTED GROUPER (Epinephelus tauvina)
Mean egg diameter 0.75mm
Standard length at hatching 2.25mm
Metamorphosis completion 30–40 days from hatching at 27–31°C
Source of feeding example cited: Akatsu, Al-Abdul-Elah & Teng (1983) Temperature 27–31°C. Salinity 25ppt. Larval density 52/1 day 1–20, reducing to 1/1 from day 21–40. Survival 31–55% at 27–29°C day 1–12; 85–91% survival at 31°C from day 19–33.
Further reading: Hussain & Higuchi (1980), Chen et. al., (1977)

Species:GIANT SEAPERCH/SEA BASS (Lates calcarifer)
Mean egg diameter 0.8mm
Standard length at hatching 1.5mm
Metamorphosis completion 18–20 days from hatching at 27°C
Source of feeding example cited: Tattanon & Maneewongsa (1982) Temperature 27°C. Salinity 20ppt. Survival 85% egg hatching rate, 37% day 1–7, 81% day 8–15, 70% day 16–23, 85% day 24–30. Larval density 30–40/1 day 1–7, 15–20/1 day 8–15, 5–10/1 day 16–23, 2–5/1 day 24–30.
Further reading: FAO/SCS (1982), Bagarinao & Kungvankij (1986), Moore (1982)

Species:MILKFISH (Chanos chanos)
Egg diameter 0.8–1.2mm
Standard length at hatching 3.5–4.3mm
Metamorphosis completion 18–21 days from hatching at 26–29°C
Source of feeding example cited: Juario et. al., (1984) Temperature 26–29°C. Salinity 34ppt. Larval density 8–17/1 (fertilized egg incubation). Larval survival 19–56% (over 21 days)
Further reading: Vanstone et. al., (1977), Chaudhuri et. al., (1978), Liao et. al., (1979), Duray & Bagarinao (1984), Pantastico, Baldia & Reyes (1986), Santiago, Banes-Aldaba & Songalia (1983), Juario & Storch (1984)

Species:FRESHWATER PRAWN (Macrobrachium rosenbergii)
Mean egg diameter 0.6–0.7mm
Standard length at hatching 1.9–2.0mm
Metamorphosis completion 25–45 days from hatching at 25–30°C
Source of feeding example cited: AQUACOP (1984) Temperature 29–31°C. Salinity 10–12ppt. Larval density 100/1 (initial) Survival 51–74% after 37–40 days. Size at P1 7–8mm standard length.
* Diet fed at 0800 and 1000h. Typical diet: 20% squid flesh, 20% shrimp flesh, 20% hens egg, 20% herring roe, 2% vitamins, 1% minerals
15% cod liver oil, alginate 2% (all on dry weight basis).
Further reading: New & Singholka (1982), Menasveta & Piyatiraatitivokul (1980), Fujimura & Okamoto (1970), New (1982), Nai-Hsien Chao & Liao (1977), Uno & Kwon Chin Soo (1969), Adisukresno, Escritor & Mintardjo (1982), Dungan, Hagwood & Frakes (1975), Hagwood & Willis (1976), Kwong (1984), Tansakul (1983), Cohen, Finkel & Sussman (1976), Meyers and Hagwood (1984).

Mean egg diameter 0.25–0.29mm
Standard length at hatching 0.3–0.4mm
Metamorphosis completion 10–15 days from hatching at 25–30°C
Size at P1 4–5mm total length
Source of feeding example cited: Vielka Morales de Ruiz - Personal communication, Panama, March 1988). Shrimp species: P. vannamei. Temperature 27–29°C. Salinity 30–35ppt. Larval density 60/1 (nauplii). Survival 50% from nauplii to Pl stage.
Further reading: Kitani (1986. 1986a), Kafuku & Ikenoue (1983), Treece (1985), AQUACOP (1984), Heinen (1976), Leger, Sorgeloos & Chamoro (1987). Liao & Hung (1973).

MARINE FISH LARVAE - JAPAN (Watanabe, Kitajima & Fujita, 1983)
Further reading: Kuronuma and Fukusho (1984), Fujita (1979)

Initial larval density 100–120/l. Temperature 25–29°C. Salinity 35ppt. pH 8.2
Survival rate:65–80% from nauplius to P4 stage for P. merguiensis, P. indicus, P. vannamei and P. stylirostris 45% from nauplius to P4 for P. monodon.

Initial larval density 100–120/1. Temperature 27–29°C. Salinity 25–35ppt pH 7.8 – 8.2. No data on survival given.
Further reading: Chamberlain, Haby & Miget (1985), Simon (1981), Yang (1975), Kuban, Lawrence & Wilkenfeld (1985), Sanchez (1986), Mock, Revera & Fontaine (1980), Wilkenfeld, Lawrence & Kuban (1984)

MARINE SHRIMP LARVAE - PHILIPPINES (Kungvankij et. al., 1986)
Initial larval density 100–150/1. Temperature 26–31°C. Salinity 30–32 ppt. pH 7.5–8.5 Survival 30–40% to P1 for P. monodon.
Further reading: Liao (1984), Yap (1979), SEAFDEC (1984), FAO/SCP (1982a), Mochizuki (1978), Tobias-Quinitio & Villegas (1982).
*  Equivalent to a mysis consumption of 20–50 nauplii/day
** Equivalent to a mysis consumption of 100–200 rotifers/day

In the past, attempts to replace live food organisms with inert or artificial complete diets have resulted in reduced larval survival, delayed larval development, and often total larval mortality (New, 1976, Seidel et. al., 1980). To a large extent, this has been due to the use of inadequate feed management techniques (ie. infrequent feed presentation and water exchange, poor understanding of larval feeding behaviour and physical feed requirements), poor feed water stability and a consequent loss of water soluble nutrients and increased water pollution. However, recent improvements in our understanding of larval nutrition (ie. high dietary requirement for highly unsaturated fatty acids - Leger, Sorgeloos and Chamorro, 1987, Cho, Cowey and Watanbe, 1985), larval digestive physiology (ie. possible dietary requirement for purified enzyme preparations/ enzyme ‘triggers’ and for soluble or highly digestible dietary feed ingredients - Cruz-Ricque and AQUACOP, 1987, Maugle et. al., 1982, 1983, 1983a, Kanazawa et. al., 1982, Jones, Kurmaly and Arshard, 1987, Dabrowski, 1984), larval feeding (ie. importance of frequent feeding and tank design - Charlon and Bergot, 1984, Teshima and Kanazawa, 1983, Dabrowski and Kaushik, 1985), and larval feed manufacturing techniques (Meyers, 1979; Cho, Cowey and Watanabe, 1985; Mylvaganam, 1988), has stimulated renewed interest in the development of artificial larval diets to replace live food organisms during the hatchery cycle.

Two new artificial diet feeding systems have been introduced recently as ‘viable’ alternatives to the live food production system: 1) the exclusive useof a rehydratable microencapsulated or microparticulate larval diet (Cho, Cowey and Watanabe, 1985; Mylvaganam, 1988; Meyers, 1979), and 2) the exclusive use of a crustacean tissue suspension (Hameed Ali, Dwivedi and Alikunhi, 1982; Tacon, 1986a; Kungvankij et. al., 1987). Although both methods rely on feeding a single, non-living food item for the entire larval culture phase, they differ in the feed resources used and the degree of sophistication of feed preparation. For a review of microencapsulation and microparticulate larval diet preparation techniques see Jones, Kanazawa and Rahman (1979), Scura, Fischer and Yunker (1984), Jones et. al., (1984), Chow (1980), Gatesoupe and Luquet (1977), Teshima and Kanazawa (1983), Kanazawa et. al., (1982, 1982a), Cho, Cowey and Watanbe (1985), Le Moullac et. al., (1987) and Galgani and AQUACOP (1988). For example, Table 8 summarises the results of Kanazawa et. al., (1982) with P. japonicus larvae using a variety of microencapsulated and microcoated artificial diets.

Table 8. Effect of different artificial diet feeding regimes on the growth and survival of Penaeus japonicus larvae (initial larval density 100Z1/800ml, salinity 34–35ppt, temperature 27–29°C; source: Kanazawa et al 1982a)

Diet typeIngredientSize(um)Feeding concentration mg/larvae/daySurvival % at P1Developmental stage reached
Nylon microencapsulated diet 1Mysid extract/hens egg 250–1000.44–0.60 378P1 (8 days)
Nylon microencapsulated diet 1Diet A/hens egg 450–1000.44–0.6070P1 (8 days)
Zein microencapsulated diet 5Mysid extract100–1500.3342P1 (8 days)
Zein microencapsulated diet 6Diet A100–1500.330M1 (5 days)
Zein microencapsulated diet 6Diet B 7100–1500.330M2 (5 days)
Zein microcoated diet 8Diet A10–500.2094P1 (8 days)
Zein microcoated diet 8Diet B10–500.2075P1 (8 days)
Live food 9Chaetoceros, Artemia--95P1 (7 days)
No food (starved)---0Z2 (3 days)

1 Nylon-protein encapsulated diets were prepared by the interfacial polymerisation procedure of Chang, MacIntoshand Mason (1966) as modified by Jones et. al., (1976) using 1, 6-diaminohexane, sebacoyl chloride and a suspensionof the finely ground (less than<10–20um) diet to be encapsulated.
2 To 2g of mysid extract or diet A, chicken egg (1.34g in dry weight) was added as the homogenate (20ml) of wholechicken egg-distilled water (1:1, v/v) and encapsulated.
3 To supply a concentration of 500–700 capsules/ml water.
4 For the composition of diet A see Table 5 (formulation 19: Kanazawa, Teshima and Tokiwa, 1977).
5 Zein microencapsulated diet (ethanol method); the powdered diet (6g) was mixed with zein (1.2g) dissolved in76% ethanol (74ml) with continuous stirring, and then distilled water (150ml) was added drop by drop to thissuspension to form the Zein-encapsulated diet.
6 Zein microencapsulated diet (sodium hydroxide method); the powdered diet (7g) was suspended in a sodium hydroxidesolution (pH 12, 70ml) containing zein (1.4g) with continuous stirring by means of a magnetic stirrer. The suspensionwas diluted with distilled water (120ml) and acidified with acetic acid to a pH value of 4.5 to form the zein-encapsulated diet.
7 Commercial diet for P. japonicus (Evian, Kyowa-hakko Kogyo Co. Ltd).
8 Zein microcoated diets were prepared by first drying, crushing and sieving the dietary ingredient mixture. To thepowdered diets (less than <10–20um; 8g), zein (5g) dissolved in 60% ethanol (25ml) was added, mixed thoroughly, andthenheated in an oven at 40°C for 24–48h. The dried diets were then powdered into particles of 10–50um.
9 Control group were fed on Chaetoceros gracilis (50–70,000 cells/ml) until mysis stage and then on newly hatched Artemia nauplii (15 nauplii/ml).

2.4.2 Dietary feeding regimes and allowances

Maximum benefit from complete diet feeding will only be achieved if the food is ingested in its entirety by the fish or shrimp species in question. To obviate the difficulties of feed disintegration and solubilization within water it is essential therefore that the period the feed remains in water is kept to a minimum and that the feed is presented to the fish or shrimp in the correct physical form (ie. size) and in such a manner over the working day so as to elicit a maximum feeding response and optimal growth and feed efficiency. For example, Figure 6 shows the effect of dietary feeding rate (expressed as a percentage of the body weight per day) on food conversion efficiency (feed intake divided by live weight gain) and specific growth rate ([loge final body weight - loge initial body weight] divided by the total growth period in days, multiplied by 100) of common carp (C. carpio) post-larvae and fry. From the data presented it is clear that for each species age class and diet there is a dietary feeding rate range where both growth and feed efficiency are optimal. A similar relationship has also been observed between feeding frequency and growth; the frequency of food presentation required to promote optimum growth and feed efficiency varying with diet and age class from juvenile grouper (E. tauvina) which require ‘satiation’ feeding (ie. ad libitum or feeding to appetite) only once every two days on a trash fish diet (Chua and Teng, 1980), to the post-larval phase of common carp and the African catfish (C. lazera) which require continuous or very regular feeding throughout a 24-h cycle (Bryant and Matty, 1981; Yamada, Tanaka and Katayama, 1981; Hogendoorn, 1981). Furthermore, Wankowski and Thorpe (1979) found a direct relationship between growth rate and feed particle size in juvenile Atlantic salmon (S. salar); the feed particle size required for maximum attack response and growth increasing in direct proportion to fish body length ( fish from 4.2 to 20.3cm in length showed maximum growth on feed particle diameters 0.022 to 0.026 × fish fork length, as compared with 0.009 to 0.018 × fish fork length for first-feeding fry of 2.8cm body length; Featherstone, 1981). A similar relationship has also been observed between mouth size and prefered food size; optimal feed sizes generally being computed as 0.4 to 0.6 of mouth width (Knights, 1983; Dabrowski and Bardega, 1984).

The importance of correct feed presentation and feeding level cannot be under emphasised; dietary failures usually attributed to formulation or manufacturing deficiencies often being the result of poor feed management on the farm (ie, due to inadequate feed particle size and feeding frequency, and over or under feeding; Charlon and Bergot, 1986; Dabrowski et. al., 1984; Uys and Hecht, 1985). In general, feeding practices have been related to the convenience of the feeding technician during his or her working day rather than to the behavioural feeding requirements of the cultured fish or shrimp species. For example, despite the nocturnal feeding behaviour of marine shrimp (Cuzon et al., 1982; Apud, Deatras and Gonzalez, 1981) and the rapid loss of water soluble nutrients from rations on prolonged immersion in water (Cuzon et. al., 1982 report a 20% loss of dry matter/ crude protein and up to 95% loss of water-soluble vitamins through leaching from a conventional pelleted shrimp ration after a one hour immersion period; see also Forster, 1972 and Jones et. al., 1984), the majority of semi-intensive shrimp farmers still only feed their animals once or twice daily (during the early morning and/or late afternoon) instead of distributing their feed at regular intervals during the night from dusk to dawn. Clearly, this situation must be remedied if maximum benefit is to be gained from complete diet feeding; farmers and researchers alike must be made aware of the nutritional and economic losses they will be incurring for every additional minute or hour that their feed remains uneaten in water.

Figure 6

Figure 6. Effect of feeding rate on growth (•) and food conversion (o) of common carp post-larvae (initial weight 15mg) and fry (initial weight 100mg) fed a commercial trout fry diet (composition: moisture 9.5%, crude protein 52.1%, lipid 8.2%, ash 11.5%) at 2-hourly intervals at 24 ± 0.5°C (Bryant and Matty, 1981)

Table 9 presents examples of some recommended complete diet feeding regimes and allowances for use within intensive aquaculture systems. However, although the information presented on feed particle size may be applied with a certain degree of confidence, the daily feeding allowances shown are diet and farm specific and as such should only be treated as very tentative guidelines by persons wishing to devise their own farm feed management programme; optimal daily feeding frequency and feed intake being dependent on the digestible energy content of the diet, water temperature, water quality (dissolved oxygen concentration), fish or shrimp size, and gastro-intestinal evacuation rate (Elliot, 1975; Gwyther and Grove, 1981; Grove, Loizides and Nott, 1978). Since fish and shrimp eat primarily to satisfy their energy requirements (assuming that the diet is palatable), it follows therefore that the digestible energy content of the diet will determine the amount of feed consumed; animals fed low energy diets requiring a higher dietary feed intake than animals fed high energy rations (Cho, Cowey and Watanabe, 1985). Consequently, since the energy requirements of an animal are directly proportional to the metabolic activity of the organism, it follows that feed intake and feeding frequency will be paced at gradually declining rates with increasing fish or shrimp size and/or decreasing water temperature (Brett and Groves, 1979; Tacon and Cowey, 1985). Thus, for animals such as tropical shrimp and fish larvae which have a very high metabolic activity and a rapid gastro-intestinal evacuation rate, it is essential that their high energy requirements are met by more or less continuous saturation feeding. However, the success of such a feeding strategy will in turn depend on good water management (see Charlon and Bergot, 1984). Clearly, considerable further studies are required in this important area of feed management. For example, only by reducing the ‘normal’ dietary feed intake of rainbow trout broodstock by one half, egg fecundity can be increased with no loss in larval survival (Springate and Brommage, 1984; 1985).

For information on conventional hand/mechanical feed application methods readers should refer to the excellent reviews of Varadi (1984), New (1987), Rodeia (1985) and Berka (1973), and the papers of Charlon and Bergot (1986) and Meriwether (1986). On a general basis, the feeding technique employed will depend on the intensity and size of the farming operation, and service /labour availability and cost. However, when ever possible hand feeding is recommended so that regular checks can be kept on feeding behaviour, water quality and fish/shrimp health.

Table 9. Selected examples of recommended complete diet feeding regimes and allowances

1. Rainbow trout (S. gairdneri) 1

Fish size
Feed composition
(% CP, EE, CF, Ash)
Feed size
(mm diam)
Feeding frequency
(No. feeds/day)
Feeding rate2
(% body weight/day)
0–0.553,12,0.5,190.5–0.8 granule182.1–6.3
0.5–453,12,0.5,190.8–1.8 granule162.1–6.3
4–650,12,1.5,141.8 shortcut pellet122.0–6.0
6–1050,12,1.5,141.8 pellet101.8–5.3
10–1547,12,2.5,142.4 pellet81.6–4.7
15–2547,12,2.5,142.4 pellet81.4–4.0
25–5045,12,4,133.2 pellet61.2–3.5
50–7545,12,4,133.2 pellet61.1–3.1
75–10045,12,4,134.8 pellet41.0–2.8
100–15045,12,4,134.8 pellet40.9–2.5
150–25045,12,4,136.4 pellet30.8–2.3
250–50045,12,4,136.4 pellet20.7–1.9
500–100045,12,4,138.0 pellet20.6–1.5
1000+45,12,4,139.6 pellet20.5–1.3

1 Source: Tyrell, Byford & Pallet Ltd., Norfolk, England (February, 1985)
2 Feeding rate range presented is for 4°C–20°C Further reading: Billard (1986), Cho, Cowey and Watanabe (1985), Zendejas Hernandez (1987), Hilton and Slingerv (1981), Klontz, Downey and Focht (1983), NRC (1981), Storebakken and Austreng (1987).

2. Atlantic salmon (S.salar) 1

Fish size2
Feed composition
(% CP, EE, CF, Ash)
Feed size
(mm diam)
Feeding rate 3
(% body weight/day)
0–0.554,19,1,100.3–0.6 granule1.4–6.5
0.5–1.254,19,1,100.6–1.1 granule1.0–4.5
1.2–554,19,1,101.1–1.5 granule0.7–2.9
5–1254,19,1,101.5–2.0 granule0.5–2.2
12–4054,19,1,102.0–3.0 / 1.5 pellet0.3–1.5
40-transfer50,17,1,92.0 pellet0.3–1.1
Transfer-9050,17,1,92.0 pellet0.6–2.8
90–15046,16,1,103.0 pellet0.5–2.4
150–25046,16,1,105.0 pellet0.4–2.0
250–40046,16,1,105.0 pellet0.4–1.7
400–70046,16,1,106.5 pellet0.3–1.5
700–100046,16,1,106.5 pellet0.3–1.3
1000–200046,16,1,108.0 pellet0.2–1.0
2000+46,16,1,108.0 pellet0.2–0.8

1 Source: Ewos Baker Ltd., Bathgate, Scotland (February, 1984)
2 Freshwater phase 0–40g transfer, thereafter sea-water grow-out Further reading: Thorpe and Wankowski (1978), Wankowski and Thorpe (1979), Cho, Cowey and Watanable (1985), Featherstone (1981), Piper et. al., (1982), Klontz, Downey and Focht (1983), NRC (1981), Storebakken and Austreng (1987a)

3. Tilapia (O. niloticus/O. mossambicus)

Fish size
Feeding rate 1
(% body weight/day)
Fish size
Feeding rate 2
(% body weight/day)
Fish size
Feed size 3
(mm diam.)
0–530 reducing to 20<2510 reducing to 80–1<0.5–1.5
5–2014 reducing to 1225–1506 reducing to 41–301–2
20–407 reducing to 6.5150–200320–1202
40–1006 reducing to 4.5>2002100–2503
100–2004 reducing to 2  >2504
200–3001.8 reducing to 1.5    

1 Source: After Melard and Philippart (1981) cited by Coche (1982). Data is for O. niloticus in tanks and cages at 27–31°C using a 46% protein commercial fish ration for the entire culture phase
2 Source: Personal communication of Campbell cited by Coche (1982)
3 Source: For O. mossambicus/O. niloticus (Jauncey and Ross, 1982). These authors cite the studies of Macintosh (1982) and Macintosh and De Silva (1982) who recommend a feeding rate of 36% body weight/day for first feeding fry, decreasing to 12% by day 20, to 6% for fish above lg, and to 3% for 50g fish (the results are based on the use of a commercial trout fry feed for the entire culture period (diet contained 49% crude protein). The same authors suggest a daily feeding frequency of 4–8 feeds/day for fry, 4–5 feeds/day for fingerlings, and 2–3 feeds/day for adults under intensive culture.
Further reading: Philippart and Melard (1987), Pullin and Lowe-McConnell (1982), Zendejas Hernandez (1987), Melard (1986), Macintosh and De Silva (1984).

4. Channel catfish (I. punctatus)

Water temperature
Fry or fingerlings 1Food size fish 1Fish size
Feed size
Feeding frequency
Feeding * rate
Feeding frequency
Feeding rate
10–13alternate days2alternate days1  
<9once/3–4 days1once/3–4 days0.5  

1 Source: Dupree (1984)
2 Source: Winfree and Stickney (1984)
* Murai and Andrews (1976) reports an optimal feeding frequency of 8 feeds/day (once every 3 hours; feed intake 8–10% body weight/day) for < 1.5g fish, and 4 feeds/day for 1.5–4g fish (once every 3 hours between 8.00am and 5.00pm; feed intake c. 5% body weight/day). These experiments were performed at 27±0.5°C using a commercial fry feed (composition not given). Further reading: Robinson and Lovell (1984) and Robinson and Wilson (1985).

5. African catfish (C. lazera/gariepinus) 1

Days from first feedingFeed composition
(%CP, EE)
Feed size
Feeding frequency
Feeding rate 2
(% body weight/day)
0–455.4,9.11125–2006 (once every 4h)25
5–855.4,9.11200–2506 (once every 4h)25
9–1155.4,9.11250–3506 (once every 4h)25

1 Source: Uys and Hecht (1985) - experiment was conducted at 23±0.5°C using newly hatched larvae(larvae start exogenous feeding 4 days after hatching).
2 Hogendoorn (1981) reports an optimal feeding rate of 10% body weight/day for fingerlings (0.5–10g in weight) fed a commercial ration (‘Trouvit starter’; 50% protein, 9.5% lipid) at 30°C and with continuous 24-h feeding.
Further reading: Janssen (1985), Viveen et al., (1985), Machiels and Henken (1986).

6. European eel (Anguilla anguilla)

Fish size
Feed size 1
(mm diam)
Eel stage and sizeFeed size 2
(mm diam)
0–0.50.25–0.71First feeding elversNatural and/or paste feeds
0.5–10.35–1.00Weaned elvers (0.2g)0.43–0.85
1–50.50–1.00Fingerlings (0.2–5g)0.86–1.40
5–100.71–1.40Fingerlings (2–10g)2mm pellets + 0.51–0.85mm
  Eels (10–100g)2.6mm pellets

1 Source: Kastelein (1983)
2 Source: Knights (1983)
Feed particle sizes recommended by EWOS AB, Sodertalje, Sweden: 0.25–0.8mm crumble for 0–1.5g eels, 0.8–1.4mm crumble for 1.5–10g eels, 1.4–2.4mm crumble for 10–60g eels, and 2.4–4.0mm crumble for 60–300g eels (feed composition: crude protein 48%, lipid 17.5%, fibre 1.0%. ash 9.0%; 1984–85 Product line).

7. Common carp (C. carpio)

Fish larval size
Feed composition
(% CP,EE,CF,Ash)
Feed size
(mm diam)
Feeding rate
age, day

1 Source: EWOS AB, Sodertalje, Sweden (1984–85 Product line) - feed to be distributed by automatic feeder (4 times/hour, 15 hours/day) or by hand feeding (approximately 10 times/day, 15 hours/day). Feeding rate described is for use at 25°C.
2 Further reading: Charlon and Bergot (1984), Bryant and Matty (1981), Charles et. al., (1984), Dabrowski, Bardega and Przedwojski (1983), Appelbaum (1977), Zendejas Hernandez (1987), Jhingran and Pullin (1985), New (1987).

8. Kuruma shrimp (P. japonicus) 1
Shrimp size
Daily feeding rate (% body weight/day)

1 Source: Boonyaratpalin et. al., (1980) - feeding regime for shrimp in circular running ponds in Kagoshima, Japan, using a high protein diet (ie. Kyowa Hakko Kogyo Co. Ltd., produces shrimp feed containing ≥60% protein, ≥6% lipid, <7% fibre, 15% ash and 9% moisture, with a water stability of 3 days in water. Feed is normally fed once daily, before sunset. Feed sizes used by Kyowa Hakko Kogyo Co. Ltd include:

P1-P5 - crumble (pass through 60 mesh)Further reading: Sedgwick (1979), Lim and Pascual (1979), Pascual (1983), New (1987), Taechanuruk and Stickney (1982), Kafuku and Ikenoue (1983), Liu and Mancebo (1983), Spotts (1984).
P5-P20 - crumble (pass through 40–60 mesh)
0.01g-0.015g- crumble (pass through 20–40 mesh)
0.015g-1.0g - crumble (pass through 10–20 mesh)
1g–2g- crumble (pass through 10-on)
Above 2g- pellet (2.5mm diameter × 20 length)

9. Larval shrimp (general) 1

Larval stageFeed size
(um diam)
Feeding rate 2
(g feed/tonne water/feeding)
Feed concentration
(feed particles/ml)

1 Source: Jones et al., (1984) - feeding regime for the use of a commercial microencapsulated larval shrimp diet (Frippak Feeds, Basingstoke, Engl and). Feed capsule composition given as 49% crude protein, 13% lipid,and 11% ash.

2 Based on 5 feedings per day.
Further reading: Teshima and Kanazawa (1983), Scura, Fisher and Yunker (1984) and Tacon (1986a).

2.5 Economics of complete diet feeding and choice of strategy

2.5.1 Objectives and cost of compound feed manufacture

According to Palmer - Jones and Halliday (1971) the profitability and success of compound feed production depends on the fulfillment of three often conflicting objectives, namely:

Although the economics of feed manufacture will vary from country to country depending on raw material ingredient costs and processing and sales costs, full economic analyses must be undertaken to justify the use or not of a particular feed manufacturing process. Clearly, the possible additional cost of for example fine grinding or extrusion pelleting over standard grinding or steam pelleting must be economically justified by an equivalent improvement in animal survival, growth or feed conversion efficiency and consequently income over total outlay. To facilitate such a decision, Table 10 presents three examples of economic analyses undertaken for the small-scale manufacture of compound farm animal feeds and fishfeeds, respectively. For additional information on the economics of compound feed manufacture readers should refer to Patton (1976), Horn (1979) and Crampton (1985).

2.5.2 Economic considerations

Since food and feeding costs generally constitute the highest operating cost item of intensive fish and shrimp grow-out farming operations (Kim, 1981; Shang, 1983; Huguenin and Ansuini, 1978; Chua and Teng, 1980; Sungkasem, 1982), it is essential that the feed is formulated and presented in such a manner so as to provide maximum production efficiency at a minimum cost. Comercial fish and shrimp farmers are concerned therefore with converting fish or shrimp feed into fish or shrimp flesh as quickly and as efficiently as possible. However, the relative importance of growth rate and feed conversion efficiency or survival (in the case of larvae/juveniles) will depend upon the cost of the feed in relation to the market value of the farmed product. For example, Figure 7. shows the market value of different salmonid species, and of different sizes, in the UK (data from Crampton, 1985). A comparison of the feed costs and market value of the respective fish age class shows, in the case of Atlantic salmon (Salmo salar) smolts, that a relatively low cost feed item is converted into a very high cost salmon smolt; here, the farmer is therefore interested in maintaining high growth rate so as to increase turnover (and also reducing fixed/overhead costs). Under these conditions reduced feed costs or increased feed efficiency would not have much effect on profitability, where as increased growth rate and survival would have a significant effect on profitability (a similar situation exists for the mass hatchery production of shrimp or prawn post-larvae). However, the reverse would be true for trout growers; the difference between the price of trout feed and the market value of trout flesh being much less. Here, increased feed efficiency would be more important than increased fish growth.

Table 10. Economic analysis of compound feed manufacture

1. Capital and operating costs for compound animal feed manufacture (£ Sterling 1970) 1

Plant modelABCD
 Feed output per hour (tons)12.558
 Feed output per year (tons)2,4006,00010,50016,800
 Feed typeDairy compoundDairy compoundPoultry productsPoultry products
Capital costs£% Total capital costs£%Total capital costs£%Total capital costs£% Total capital costs
1.Factory building1,0352.51,4641.41,9601.24,0651.6
3.Machinery and equipment 26,74516.426,35925.633,44719.940,72816.0
4.Spare parts1,6003.92,0001.92,6501.64,2001.6
5.Installation cost4751.19500.91,3000.82,5001.0
6.Contingencies 39432.32,4392.43,5432.15,0952.0
7.Total fixed capital19,798 51,212 74,400 106,988 
8.Working capital 421,43352.051,60450.293,80655.8147,53058.0
9.Total capital invested41,231 102,816 168,206 254,518 
Annual operating costs£%Total operating costs£%Total operating costs£%Total operating costs£%Total operating costs
10.Raw materials64,72274.0161,80576.9302,54979.0484,07880.4
12.Electricity (a) demand charge3150.361,1450.541,4720.381,7300.29
               (b) current charge5940.687270.341,0530.271,2540.21
13.Spare parts 58000.911,0000.471,3250.352,1000.35
14.Product delivery1,8002.14,5002.17,8752.112,6002.1
15.Manpower 67,2008.211,0505.214,9003.916,6002.8
16.Maintenance 79251.13,1231.54,1811.15,4350.90
17.Insurance and administration 86210.711,5770.752,6290.694,0250.67
18.Advertising 93,2363.78,0903.815,1273.924,2044.0
19.Rent on land370.04700.031210.031940.03
20.Unforseen 104,0824.79,8294.717,8684.728,1014.7
21.Interest on working capital 111,7152.04,1282.07,5042.011,8022.0
22.Total operating costs 1287,447 210,544 382,729 601,923 
  £ £ £ £ 
23.Sinking fund (a) buildings 13940 1,824 3,135 5,103 
                  (b) machinery1,140 3,708 4,782 6,135 
                  (c) total2,080 5,532 7,917 11,238 
24.Total outlay 1489,527 216,076 390,646 613,161 
25.Cost/ton of output 1537.3 36.0 37.2 36.5 
26.Price/ton at 15% profit 1639.9 38.6 39.6 38.8 

1 Source: Tropical Devlopment and Research Institute, London (Palmer-Jones and Halliday, 1971).
2 Machinery and equipment: includes grinding, blending, mixing, pelleting and steam production equipment.
3 Contingencies: 5% of rows 1–5.
4 Working capital: calculated as one quarter annual operating costs, rows 10–20.
5 Spare parts: annual requirement calculated as one half row 4.
6 Manpower: includes management, clerical, supervisory, semi-skilled and unskilled personnel.
7 Maintenance: calculated as 2.5% of rows 1–2 plus 10% of row 3.
8 Insurance and administration: insurance and administration: insurance is 1.5% of row 7. The rest is based on 0.5% of row 10.
9 Advertising: 5% of row 10.
10 Unforseen: 5% of the sum of rows 10–19.
11 Interest on working capital: 8% of row 8.
12 Sum of rows 10–21.
13 Sinking fund contribution: this sum covers the depreciation and interest payments on the cost of buildings and plant. It consists of a series of constant annual sums which completely amortise the buildings in 25 years and plant and machinery in 15 years, when interest is paid on the repaid capital at 8% per year.
14 Row 22 plus row 23c.
15 Row 24 divided by annual output.
16 Row 24 plus 15% of row 9 divided by annual output. Note that in this costing no allowance has been made for taxation. It will normally be necessary to use a greater mark-up than 15% in order to allow for the incidence of tax.

2. Estimates of production costs for the small scale manufacture of pelleted fish feed in a ‘typical’ developing country (£ Sterling, 1985)

Production itemFeed output in tonnes/month
(No. of men)(2) (2) (3) (3) (4) (4) 
  a) Fixed charge150.7150.4150.3150.2150.2150.1
  b) Consumption charge351.7701.81051.81401.81751.82101.8
Miscellaneous handling charges100.5200.5300.5400.5500.5600.5
Raw materials150074.0300076.0450076.1600076.8750076.7900076.9
Production cost/tonne203 197 197 196 196 195 

Source: Tropical Development and Research Institute, London (J. Wood, Personal Communication, February, 1985).
In this example, no allowance has been made for buildings, purchase of vehicles or repayment of the loan for the purchase of the pelleting plant. The packaged pelleting plant for which the above production costs refer, has a batch mixing capacity of approximately 150–180kg and an output of approximately 200kg/h of 3mm pellets. The cost analysis for the plant (February 1985) is as follows: package unit - £17,500 (including 15HP hammer mill, 4HP horizontal mixer, 10HP pelletizer, auger, elevator, cooling bin, cyclones and control box), shipment cost - £2500 (CIF UK-Pakistan), spares for package unit - £2,500, tool kit - £300, beam scales (x2) - £2,500, bench scale - £1,000, sack trucks (x2) - £400, pallet truck - £850, bag stitcher - £1,000, infra red moisture balance (optional) - £1200, refrigerator for vit ins/mineral storage - £250. Total cost analysis for feed package plant - £30,000.

Notes: 1. Feed package plant has output of approximately 20–25 tonnes/month of three mm pellets. 2. Electricity fixed charge - estimate for maximum demand or other standard charge. 3. Consumption charge at £0.05/kwh and 70kwh/tonne. 4. Labour at £50/man/month. 5. Miscellaneous handling charges at £1.0/tonne. 6. Bag charges at £0.3/25kg bag, 40 bags/tonne = £12/tonne. 7. Administration add £5/tonne. 8. Raw materials estimated at £150/tonne for mixed feed of 30% crude protein. 9. Transport cost at £10/tonne. 10. Profit at £10/tonne.

3. Economic analysis of small-scale fish feed manufacture in the Central African Republic (C.F.A. Franc, 1984) 1

(a) Production of dry pelleted fish feed - 200kg/day, 50 tons/year

Fixed costs  Cost (F)/annum
    Warehouse/housing10×15m, at 10,000F/m2, replacement period 30 years 50,000
    Pelleting machine6,885,000F, replacement period 15 years 459,000
    Grinding/mixing2,500,000F, replacement period 15 years 166,667
  Interest, 10%67,567
  Grand total743,234
Operating costs   
    Labour/workmen (2)25,000F/month each 600,000
    Pelleting machine spares, roller plus drives (2 sets) at 324,000F each648,000
      Maintenance costs  50,000
      Electricity1750h/annum, at 2kw/h and 50F/kw 175,000
    Mixer/grinder spares-hammers (3 total), at 8,000F each18,000
      Sieves (2)25,000F each 50,000
      Electricity - grinding 500h/annum, at 5.5kw/h and 50F/kw137,000
                     - mixing 1h/day, 250h/annum, 1.5kw/h and 50F/kw18,750
    Ingredients + transport 5,042,950
    Unforseen/extras15% 1,011,030
  Grand total7,751,230
Pelleted food cost (based on all fixed and operating costs)
Fixed costsCost(F)/yearCost (F)/kg feed% total% operating
Operating costs    
Grand total8,494,464169.9100100

(b) Production of moist pelleted fish feed - 500kg/day, 125 tons/year, 50 weeks

Fixed costs  Cost (F)/annum
Store room10×15m, at 10,000F/m2, replacement period 30 years 50,000
Grinder/mixer2,500,000F, replacement period 15 years 166,667
Pelleter/mixer3,500,000F, replacement period 15 years 233,333
  Interest 10%45,000
  Grand total495,000
Operating costs   
Labour/personnel (2)25,000F/month each 600,000
Grinding/mixing spares - hammers (6) at 6000F each 36,000
Sieves (4)25,000F each 100.000
Electricity - grinding 1250h/annum, 5.5kw/h and 50F/kw 343,750
 - mixing 2h/day, 1.5kw/h and 50F/kw 37,500
Extruding/mixing - maintenance 150,000
Electricity7h/day, 1.5kw/h and 50F/kw 131,250
Ingredients125,000kg at 84.9F/kg 10,612,500
Transport125,000kg at 16F/kg 2,000,000
Unforseen/extras 15%  2,101,650
  Grand total16,112,650

Pelleting food cost (based on all fixed and operating costs)

Fixed costsCost (F)/yearCost (F)/kg feed% total% operating
Operating costs    
Grand total16,607,650132.8100100

(c) Production of dry mixed flour - 1000kg/day, 250 tons/year at 250 days

Fixed costs  Cost (F)/annum
Store room10×20m, at 10,000 F/m2, replacement period 30 years 66,667
Mixer/grinder2,500,000F, replacement period 15 years 166,667
  Interest 10%23,333
  Grand total256,667
Operating costs   
Labour/personnel (2) 25,000F/month each 600,000
Mixing/grinding spares - hammers (10), at 6000F each 60,000
Sieves (6)25,000F each 150,000
Electricity- grinding 1750h/annum 481,250
 - mixing 4h/day, 1.5kw/h and 50F/kw 75,000
Ingredients250,000kg at 84.9F/kg 21,225,000
Transport250,000kg at 16F/kg 4,000,000
Unforseen/extras15% 3,988,688
  Grand total30,579,938

Mixed food cost (based on all fixed and operating costs)

Fixed costsCost (F)/yearCost (F)/kg feed% total% operating
Operating costs    
Grand total30,836,605123.4100100

1 Source: Janssen (1984) - data presented is for the production of a feed for the African catfish (C. lazera)in the Central African Republic. Costs are calculated using a grinder/vertical mixer (250kg capacity) and apelleting machine (California Pellet Mill) with a production capacity of 200kg pellets/day. The compositionof the diet for which the analyses have been made include: brewery draft 10%, rice bran 15%, maize 7.25%,cottonseed cake 25%, groundnut Cake, sesame oilcake 10%, blood meal 5%, CMC (carboxymethyl cellulose) 0.25%,bicalcium phosphate 1%, burnt bone meal 1%, and salt 0.5%.

Figure 7

Figure 7. Market value (£ Sterling) of salmonids in the United Kingdom (from Crampton, 1985)

Foot note: Salmon smolts of 45g sell at £1.0 each, and so are worth £22.2/kg. Rainbow trout of 200–300g sell at £1.5/kg and 5g fry sell at £5.6/kg. Feed cost: Salmon smolt feed sells at £0.65/kg, trout fry feed sells at £0.6/kg, and trout grower feed sells at £0.40/kg. Value of fish production: fish food is ×34 for salmon smolts, ×9.3 for trout fry, and ×3.7 for trout growers.

For an indepth view of the principles of agricultural and aquaculture production economics readers should refer to Schaefer-Kehnert (1977); Shang (1981) and Shang and Merola (1987), respectively.

2.5.3 Choice of complete diet feeding strategy

For a fish or shrimp farm to run profitably it is essential that the correct dry or live food feeding strategy is employed. In general, the choice of intensive feeding strategy is based on three basic criteria:

As a guide, Table 11 summarises the major factors which should be considered when selecting a live food or dry food hatchery feeding strategy for the intensive mass propagation of marine shrimp or fish larvae.


Four basic hatchery feeding strategies are currently available for the mass propagation of marine shrimp or fish larvae from first feeding, through metamorphosis, to the post-larval stage. These include:

Each hatchery feeding strategy should be assessed as follows:



  1. Source of culture organisms
    1. Local
      • species available
      • seasonality
      • personnel requirement for collection
    2. Imported
      • dependability of supplier
      • minimum quantity of order
      • lead time on orders
      • variability in performance (ie. hatchability of cysts)
      • import restrictions (ie. licence, tax, credit facilities)
  2. Maintenance and production of culture organisms
    1. Stock cultures
      • space requirement (ie. phycolaboratory, culture room)
      • personnel requirement (ie. specialized training)
      • service requirements (ie. electricity, gas, UV, water, aircon)
      • culture media requirement (ie. inorganic salts, vitamins, antibiotics, chelating agents)
      • equipment requirements (ie. autoclave, filters, glassware, cell counter, microscope, culture vessels)
    2. Production cultures
      • extensive continuous culture (green water system) requirements (ie. fertilizers, personnel, air supply, space, tanks, backup)
      • intensive batch culture system requirements (ie. space, air and CO2 supply, personnel, fertilization, UV and light, plankton culture vessels, phycolaboratory)
    3. Survival/stability
      • survival and shelf life of stock cultures
      • survival of production cultures and frequency of batch failures
      • necessity to keep stock cultures all year round


  1. Sources
    1. Fishermen
    2. Processors
    3. Farm staff or hired labour
  2. Quality
    1. Species available
    2. Forms available
      • whole
      • heads, tails, skin, bones
      • offal
    3. Handling at source
      • icing
      • freezing
      • boxing
      • salting
      • air drying
      • storage
    4. Handling and processing on site
      • service requirements (ie. electricity, gas, air, water, backup)
      • equipment requirement (ie. mincing, blending, sieving, boiler, drier)
      • personnel requirement
      • storage requirement (ie. space, refrigeration)
    5. Nutrient content
      • proximate composition
      • particle size requirement
      • seasonal variation
      • possible contaminants and anti-nutritional factors
      • spoilage characteristics and storage life
    6. Larval feeding requirements
      • manual feeding
      • automatic feeders
      • service requirements (ie. electricity, air)
      • personnel requirements for feed preparation and feeding (ie. man hours per day)
  3. Quantity available
    1. Daily or weekly basis
    2. Seasonality
    3. Dependability of supplier
    4. Alternative species available
    5. Transport requirements for feed delivery to hatchery
    6. Minimum quantity of order


  1. Feed ingredient availability
    1. Local ingredient sources
      • nutrient content and digestibility
      • variability in composition
      • seasonality
      • particle size
      • possible contaminants and anti-nutritional factors
      • processing (ie. grinding) or cooking requirements
      • spoilage characteristics and storage life
      • storage requirements
      • dependability of supplier
      • minimum quantity of order
    2. Imported ingredients
      • nutrient content and digestibility
      • variability in composition
      • seasonality
      • particle size
      • possible contaminants and anti-nutritional factors
      • processing (ie. grinding) or cooking requirements
      • spoilage characteristics and storage life
      • storage requirements
      • dependability of supplier
      • minimum quantity of order
      • lead time on orders
      • import restrictions
  2. Feed preparation and handling
    1. Power requirement
      • electricity, gas, petroleum and steam
      • dependability of pwer supply and backup
    2. Water requirement
    3. Personnel requirement
      • training requirement
      • man hours per day
    4. Feed preparation space requirement
    5. Feed processing equipment requirement
      • grinder, hammermill, blender, mixer
      • extruder, pelletizer
      • freeze drier, solar drier, air drier, freezer
    6. Larval feeding requirements
      • manual feeding
      • automatic feeders
      • service requirements (ie. electricity, air)
  3. Feed storage
    1. Shelf life and stability
    2. Freezing and refrigeration requirement
    3. Packing requirement
    4. Maximum storage capacity
    5. Minimum production batch


  1. Source and availability
    1. Sources (ie. country)
    2. Dependability of supplier
    3. Minimum quantity of order
    4. Lead time on orders
    5. Import or credit restrictions
  2. Quality
    1. Nutrient content
      • proximate composition
      • particle size distribution
      • stability in water
      • variability in composition
      • spoilage characteristics
    2. Larval feeding requirements
      • manual feeding
      • automatic feeders
      • personnel requirement (ie. man hours per day)
  3. Storage
    1. Storage space requirement
    2. Power supply requirement (ie. electricity, gas, petrol)
      • refrigeration
      • dependability of power supply and backup
    3. Packing and shelf life of feed


  1. Behaviour of feed in water
    1. Buoyancy
    2. Aggregation/dispersion characteristics
    3. Stability and leaching characteristics
      • rate of nutrient loss
      • effect on water quality
      • inducement of algal or bacterial growth and contamination
    4. Swimming behaviour of planktonic food organisms
  2. Feed requirement for each critical growth phase
    1. Mg feed or number of food organisms per larvae per day
    2. Food density per larvae per day
    3. Particle size requirement for each growth phase
  3. Larval development
    1. Feed days required for each growth phase
    2. Larval size or weight for each growth phase
  4. Feeding behaviour of larvae
    1. Distribution of larvae within culture tank
      • even distribution
      • clumping/aggregation
      • surface/mid-water/bottom
    2. Ability to capture prey or feed particles
    3. Feeding incidence of larval population (%)
    4. Visibility of faecal strands
    5. Feed palatability and attack response
    6. Abnormal swimming behaviour
    7. Incidence of cannibalism
  5. Larval survival
    1. Mean survival rate (%) for each critical growth phase
    2. Frequency of mass larval mortalities and batch failures
    3. Incidence of pathogenic infections related to poor water quality resulting from poor diet stability
    4. Incidence of larval deformities
      • scoliosis/lordosis
      • short body dwarfism
      • tissue wasting disease (pin heads)
      • moulting capability
      • frequency size distribution
  6. Additional hatchery service requirements related to feeding option used
    1. Water exchange (%) frequency
    2. Aeration
    3. Lighting
    4. Tank cleaning
    5. Water sterilization
    6. Use of antibiotics


  1. Capital (fixed) costs, related to feeding option1
    1. Land - total hatchery area devoted to live food production, feed preparation and storage
    2. Structures - shed, store, laboratory, tanks etc. devoted entirely to live food production, feed preparation and storage, installation cost
    3. Machinery/equipment - pelletizer, grinder, feed dispensers, blender, boiler, silos, oven, freeze drier, autoclave, refrigerator, freezer, pumps, filters, microscope, air conditioner, mincer, sieves, etc. directly associated with feeding option
  2. Operating (variable) costs related to feeding option
    1. Personnel - manpower requirement, including level of technical skill required
    2. Energy - electricity, fuel and oil
    3. Feed procurement, handling (delivery), storage and processing cost. Additional factors which may also have to be taken into consideration include import duties/taxes, availability of foreign exchange and credit facilities.
    4. Maintenance and spares
    5. Fertilizers and chemicals
    6. Insurance and administration
    7. General supplies and materials
    8. Rent on land
    9. Unforseen/miscellaneous
  3. Market value of fish/shrimp and revenue from sales per year or cycle

  4. Total cash outlay of hatchery/year or cycle (includes hatchery operating costs, sinking fund, insurance etc.)

  5. Cash outlay/106 larvae produced/unit time

  6. Net income (before taxes, 3–4)

  7. Income over total outlay (%)

Source: Tacon (1986).

1 Although the capital items listed represent the total fixed capital investment for a particular feeding regime, for economic evaluation only the toal fixed or capital outlay will be considered. This outlay is primarily in the form of a sinking fund contribution, which covers the depreciation (amortization period) and loan interest payments on the cost of the land, structures and machinery or equipment over a pre-determined period. For complete financial analysis (since many capital items listed have dual functions, ie. not necessarily restricted to the feeding option alone), all aspects of the hatchery operation must be considered (ie. investment requirements such as hatchery building, larval rearing tanks and accessories, installation cost, electrical facilities including backup services, air supply, water supply, plumbing, filter systems, utilities, laboratory equipment, vehicles etc.) together with insurance costs, business permit/license fees and land taxes where applicable.

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