PART II TECHNICAL PAPERS(Cont.)

STATUS OF SHRIMP FEED DEVELOPMENT AT
BADC JEPARA, INDONESIA

by

Sri Umiyati Sumeru¹

1. INTRODUCTION

In Indonesia the production of shrimp feeds is still relatively low and undeveloped compared with the production of shrimp itself. It is for this reason that most of the shrimp feed used in intensive culture has to be imported, mainly from Taiwan. In order to ensure the success of shrimp culture, an adequate and ready supply of high quality shrimp feed is very important.

Good growth and high survival in the early stage of the life cycle of the penaeid shrimp requires highly nutritious food. At present, seed production of penaeid shrimp depends mostly on natural food. In BADC Jepara the use of Artemia flake diet has already been tried for shrimp post larvae but live Artemia nauplii still constitute the main feed.

Like other crustaceans, Penaeus monodon requires highly nutritious food for good growth and survival in the early stages of its life cycle. Artificial feed is a reliable alternative and may be used as a substitute or a supplement to live feed. However, in Indonesia artificial feed is very expensive because these have to be imported. At the Brackishwater Aquaculture Development Centre (BADC), the development of shrimp feed using locally available materials is part of its on-going activity.

In the formulation of shrimp feed, the following factors are considered:

1. availability and cost of feedstuff;
2. the proximate analysis of feedstuff; and
3. basic data on nutritional requirements of shrimp.

2. LARVAL DIET DEVELOPMENT

There are two types of artificial feed for shrimp: wet and dry. The wet product includes egg microencapsulated diet and egg custard whereas the dry product includes artificial plankton for larvae, flake diet for post larvae, pellet for juveniles and for growing to marketable size.

The use of wet feed material has several advantages. These are: (a) it can be prepared with simple equipment; (b) it is cheaper; (c) it attracts shrimp faster than dry feed; and (d) the nutrients remain intact because there is no hearing or drying involved. However, it has also several disadvantages. These are: (a) lack of stability (it breaks down easily); and (b) rapid oxidation (especially its ascorbic acid component) except if the product is frozen.

2.1 Wet diet

The simplest type of wet feed is one using only egg yolk as ingredient. This is prepared for feeding by homogenizing in a blender, then adding about 150 ml of boiling water while the blender is still running. This results in the coagulation of the egg yolk material into microparticulates. About 100 ml of chilled water is then added to stabilize the microparticles, this diet is designated as L-87-01.

Another type of wet diet that has been formulated at BADC consists of readily available basic ingredients as shown in Table 1.

¹ Chief, Milkfish Culture Sub-Section, Brackishwater Aquaculture Development Centre, Jl. Pemandian Kartini, P.O. Box 1, Jepara, Indonesia

Table 1. Wet diet feed formulation, L-87-02

All the dry ingredients except for the vitamins and antibiotics are mixed with the egg. The mixture is then steamed in an ordinary kitchen steamer. Upon cooling the vitamins and the antibiotics is then kneaded by hand into the steamed feed patty. This is designated as L-87-02. The nutritional analysis of the feed patty is shown in Table 2.

Table 2. Nutritional content of wet shrimp feed L-87-02
(BADC Chemist Laboratory, 1987)

The two types of wet diets were tested on Penáeus monodon larvae from zoea to post larval stage. The steamed patty (L-87-02) was tested using two methods of application. One, direct feeding by crumbling the patty in the larval rearing water. Two, by homogenizing 100 g patty in 200 ml water in a blender to produce a feed suspension. Result of the feed testing showed that the simple egg yolk feed (L-87-01) gives better result than L-87-02 when fed directly. However, L-87-02 feed in suspension form are better results than the egg yolk diet as shown in Table 3. The larvae were also observed to be healthiest when L-87-02 was fed in suspension form.

Result of feed testing when fed to shrimp larvae at each stage of all treatment is shown below.

The results of experiment from Zoea to Mysis indicated that Diet B resulted in significantly lower survival rates than that of the control as well between B and C (a: 0.05). The result of the feeding experiment showed that feeding L-87-01 (treatment A) resulted in significantly higher survival rate over that of L-87-02 fed directly (treatment B). However, when fed in suspension form (treatment C), L-87-02 definitely resulted in better survival rate than L-87-01. The result of treatment C is not significantly different over the control which used commercial larval feed (Frippak) as shown in Appendix 1.

2.2 Artificial plankton

The artificial plankton was prepared by first converting the ingredient into flake form using an electro steam double drum dryer. The flakes were then pulverized using a micro-pulverizer and sieved through 100 micron screen.

An artificial plankton formulation has also been developed at BADC. The composition of this artificial plankton, designated as (L-87-03) is shown in Table 4, while its nutritional analysis compared with that of a commercial preparation (BP, Nippon Sea Farm Co.) in Table 5.

Table 3. Result of the survival rate (%) of shrimp larvae using egg yolk,
L-87-01, L-87-02 and control

Remarks:
A — egg yolk, L-87-01 (suspension)
B — wet diet feed formulation, L-87-02
C — L-87-02 (suspension)
D — control, fed with Frippak

Table 4. Artificial plankton formulation

Table 5. Artificial plankton analysis
(BADC Chemist Laboratory, 1987)

^* BP — Artificial plankton by Nippon Sea Farm Co. Ltd., Japan
^** BADC — Artificial plankton by Brackishwater Aquaculture Development Centre

The experiment indicated that the use of artificial feed alone produce significantly lower survival rate than the use of either Tetraselmis chuii alone or T. chuii supplement (Kontara, et al., 1987). Numerically, a combination diet of T. chuii and BADC larvae diet resulted in the highest survival rate at 79.8 percent from Zoea to Mysis III. However, this was not significantly higher than that for the treatment with T. chuii + BP artificial plankton (79.0 percent) or that for treatment with Tetraselmis chuii only (77.56 percent). The combination diet of T. chuii and BADC larvae diet demonstrated its superiority in terms of final size attained by the larvae. The treatment with this combination diet resulted in the production of Mysis III larvae with an average standard length of 3.06 mm. This was statistically higher than that of T. chuii and BP (2.82 mm) and that of T. chuii only (2.78 mm). Again the treatment using only artificial plankton produced the smallest larvae at 1.63 and 1.65 mm for BADC and BP diet.

The survival rate of Penaeus monodon fed with various diets for an eight-day period (from the Zoea-1 stage to the Mysis-3 stage) is shown in Table 6.

2.3 Post larval diet

The production of flake food needs expensive equipment such as electro steam double drum dryer. One of the most popular flake diet is brine shrimp flake. This product is very expensive in Indonesia, it can cost as much as US$75 per kilogram. At BADC a brine shrimp flake (PL-87-01) has been produced using dried adult Artemia biomass and other ingredients as shown in Table 7. The nutritional composition of a shrimp flake is shown in Table 8.

Table 6. The survival rate of Penaeus monodon by artificial plankton

Remarks:
A — Tetraselmis chuii
B — BADC diet
C — BP
D — Tetraselmis chuii and BADC diet
E — Tetraselmis chuii and BP diet

Table 7. The brine shrimp flake formulation

Table 8. Nutritional composition of brine shrimp flake developed at BADC

The effect of Artemia flake diet on the growth and survival of Penaeus monodon post larvae at various feeding rates is shown in Table 9. The feeding levels are 50 percent; 75 percent, 100 percent and 125 percent total biomass with a period of 16 days. The shrimp post larvae fed with Artemia flake diet at 125 percent biomass showed weight and length gained at 2.63 mg and 12.06 mm, respectively. The average length and weight of the shrimp seed increased within the feeding level. More experiments will be necessary to determine whether the growth and survival rate can still be improved by increasing the feeding level beyond 125 percent biomass daily. The initial stage of the larvae averaged 4.87 mm in length and 0.189 mg in weight. At PL1 to PL5 with Artemia flake diet was given along with six Artemia nauplii per shrimp larvae per day. After PL5 only Artemia flake diet was used. The result of the experiments is shown in Table 9.

Table 9. The growth and survival rate of Penaeus monodon post larvae fed
with Artemia flake diet at different feeding rate for a 16-day period

2.4 Grow-out diet

Four pellet formulations of feed were prepared for testing. The composition of each formula is given in Table 10. The protein level of these feeds were: (A) 37.21, (B) 35.14, (C) 32.14 and (D) 30.16.

Table 11 shows that treatment A gave a better growth than the other treatments. From the mean initial weight of 1.523 mg, the shrimp attained 34.21 mg after one month of rearing in the container. While treatments B, C, and D show that the mean final weight were 32.14 mg; 31.17 mg and 31.14 mg, respectively. Generally, survival rates on all treatments were low, between 49.0 percent to 57.0 percent. However, in this case treatment A have the highest survival rate (57.0 percent). Looking at the two parameters, survival rate and weight of shrimp, treatment A show better results than the other treatments. This might be due to the combination of squid meal, Acetes and soybean meal as major component and protein source for treatment A.

2.5 Feed research programme

Many experiments have been done at BADC such as feed formulation for larvae, post larvae and grower diet. The feedstuffs used were locally available materials. Feeding experiments are conducted to compare the effectivity of the BADC shrimp feed with that of commercially made products. One important problem for shrimp feed is the source of attractant. BADC as a center of brackishwater aquaculture technology in Indonesia has a continuing programme to develop cheaper feeds for shrimp to eventually replace imported feeds. Several experiments on feeds formulation for shrimp and grower are necessary. This is possible to replace Taiwan feeds which are imported and expensive.

Table 10. Composition of pellet feed formulations

Table 11. Mean initial weight, final weight and survival rate of Penaeus monodon juvenile

3. ACKNOWLEDGMENT

The author is indebted to Dr. Ir Made L. Nurdjana and Mr. Wilfredo G. Yap for critical review of the manuscript and their valuable suggestions; also to thank Mr. Arief Taslihan who helped in the analysis of data for this paper.

4. REFERENCES

Kontara, E.K. and S.U. Sumeru. 1987 Makanan Buatan Untuk Larva Udang Penaeid. Infis Manual Seri. Dir. Jen. Perik. Indonesia. 29p.

Kontara, E.K., H.S. 1987 Woro and Harsito. The effect of various artificial plankton. In BADC Bulletin. Dir. Gen. of Fish. Indonesia. pp. 86–93.

Sumeru, S.U. and E.K. Kontara. 1987 Teknik Pembuatan Pakan Udang. Infis Manual Seri No. 50. Dir. Gen. of Fish. Indonesia. 26p.

Sumeru, S.U. and A. Nur. 1987 Preliminary test on the effect of feeding rate of Artemia flake diet on the growth and survival of Penaeus monodon. In BADC Bulletin. Dir. Gen. of Fish. Indonesia. pp. 94–99.

Appendix 1

1. Result of testing of wet diet feed formulation (L-87-01, L-87-02a, L-87-02b and control) for Zoea — Mysis (Z-M)

ANOVA Table

^* Significant

LSD test

LSD (0.05) = 4.83

A — B = 4.36
A — C = 3.94
A — D = 5.45*
B — C = 8.30*
B — D = 9.81*
C — D = 1.51

* Significant

2. Result of testing of wet diet feed formulation (L-87-02a, L-87-02b and control) for Mysis — PL (M-PL)

ANOVA Table

* Significant

LSD test

LSD (0.05) = 2.14

A — B = 4.46*
A — C = 0.10
A — D = 0.87
B — C = 4.36*
B — D = 5.33*
C — D = 0.97

* Significant

3. Result of testing of wet diet feed formulation (L-87-01, L-87-02a, L-87-02b and control) for Zoea — PL (Z-PL)

ANOVA Table

^* Significant

LSD test

LSD (0.05) = 2.17

A — B = 1.89
A — C = 1.75
A — D = 2.79*
B — C = 3.64*
B — D = 4.68*
C — D = 1.04

* Significant

PRELIMINARY STUDY ON THE EFFECT OF FORMULATED FEED
USING FERMENTED AQUATIC WEEDS INGREDIENT
TO THE GROWTH RATE OF RED TILAPIA

by

Sri Hartati Suprayitno¹ and Djati Widagdo

ABSTRACT

Feeding trial on red tilapia had been conducted in wooden tank covered with plastic sheet of 600 l each. Twenty fish of red tilapia were stocked per tank at the range of body weight of 4.29–5.25 g each. Four kinds of formulated feed using fermented ingredients with different protein source and commercial feed were compared in 40 days of feeding trials.

This formulated form of pellet is referred as diet A, B, C, D and E. The fish were fed the diets ad libitum, with feeding frequency two times a day. The result showed that red tilapia fed with diet A had average weight gain and daily growth rate highest compared to others. There were significant (P>0.05) with fish fed with diet A was not significant (P<0.05) with fish fed with diet E (commercial feed). There is an indication that Lemna sp. gives a better performance than Salvinia sp.

Survival rate was 100 percent in all treatments. The water quality during trials supported the growth rate performance.

1. INTRODUCTION

Tilapia nilotica had been developed since 1972 in Indonesia with the annual production of about 16 100 tons in 1986 (Fisheries Statistics of Indonesia, 1988). The main purpose to develop this species is to increase fish consumption for the people in rural areas due to its low price and easy to culture. However, in 1981 red tilapia was introduced in Indonesia because the species might give a promising result in terms of growth rate as well as its production. Besides, for the near future red tilapia might be able to become an export commodity.

Red tilapia can be cultured in intensive or extensive culture system, where both require an artificial feed usually in the form of pellet. Meanwhile, the price of commercial feed nowadays is getting high which is not feasible for red tilapia culture. Therefore, some experiments have to be conducted to find a formula with local ingredients available and certainly the production cost of feed will be reduced.

In extensive culture system, most of the farmers make their own feed for fish and as a supplement feed they use local ingredient such as ricebran. However, aquatic weeds is not yet commonly used as an ingredient for making artificial feed. Thus, the purpose of this preliminary study is to evaluate the acceptability of fermented aquatic weed in feed formula to the growth rate of red tilapia.

2. MATERIAL AND METHOD

Fifteen rectangular wooden tanks covered with plastic sheet, each tank has its own water supply with water debit about 2 liters per minute and equipped with a standing pipe for water outlet. The volume of each tank is 600 l.

¹ Chief, Freshwater Aquaculture Development Centre, Jalan Selabintana 17, P.O. Box 67, Sukabumi, Indonesia

The stocking size of red tilapia ranges from 4.29–5.52 g were used in this experiment. During acclimation, artificial feed containing 26 percent protein level was fed to the fish. Afterwards, they were randomly selected and stocked at the rate of 20 fish per tank.

Four formulated diets using fermented ingredients were prepared. For the fermentation of Salvinia sp., Lemna sp. and ricebran; 10 g of sacaromyces yeast per kg ingredient was used. The fermentation process takes about seven days under wet and unaerobic condition. While trash fish was turned to silage by adding propionic acid. Besides four formulated diets, commercial feed was fed for comparison. The percentage of formula for each diet used in this experiment is shown in Table 1.

The experiment consists of five treatments with three replicates for each treatment by means of ANOVA classification design. The fish were fed the test diets ad libitum. Feeding frequency was two times at 8:00 in the morning and 2:00 in the afternoon. Every morning siphoning had been conducted to remove all the wastes out. All the fish in each tank were weighed every 10 days to calculate the individual body weight gain and survival rate. This feeding experiment had been conducted for forty days.

3. RESULT AND DISCUSSION

The growth curves of red tilapia fed with five kinds of fermented diets for 40 days experiment is presented in Figure 1.

During the first 10 days, the fish in all treatment grew at approximately the same rate. After the second 10 days up to fourth 10 days of experiment, the growth rate of fish in the treatment A was the highest compared to others (E, C, B and D).

The average weight gain (g), daily growth rate (%) and survival rate of the fish in all treatments are given in Table 2. Fish fed with the diets A, E, C and B which the average weight gain were 3.04 g, 2.78 g, 2.42 g and 2.40 g are not significant (P<0.05). And fish fed with diet D was significant (P> 0.05) with others. There were significant (P> 0.05) differences in daily growth rate among different fermented diets. However, the daily growth rate of fish fed with diet A was not significant (P< 0.05) with fish fed with diet E (commercial feed).

Diet A had the highest average weight gain and daily growth rate compared to E, B, C and D where diet D was the poorest. It is perhaps due to protein content in diet A which was the highest, 32.1 percent (see Appendix 1). Jauncey and Ross (1982) mentioned that the protein requirement of Oreochromis niloticus with the size range from 0.5–35 g each was 35 percent and lipid requirement was 8 percent which is almost the same amount in diet A.

The increment of protein level in fermented diets has a trend in increasing the average weight gain, while the increment of using aquatic weed in diet formula 30 to 50 percent indicated lower growth performance. This result is similar to Almazan, et. al., (1986) in their experiment using various percentage of Azolla in diet formula, where the results indicate a trend in lowered growth performance with increasing Azolla incorporation. The results show that the fish fed with Lemna sp. have a better growth rate than that fed with Salvinia sp. The protein content of fermented Lemna was 28.3 percent compared to 23.9 percent of fermented Salvinia (see Appendix 2). Maria (1988) had carried out a proximate analysis of fresh Lemna with protein content under dry matter basis which was 25.5 percent. Furthermore fresh Lemna and Azolla were compared as feeds for grass carp where the result showed that Lemna was better than Azolla. Actually, the protein content of duck weed (Lemna) depends on the fertility of water body which might range from 7.4–42.6 percent (Edward, 1980). Based on previous study, red tilapia prefers eating fresh Lemna to fresh Salvinia.

Table 1. The percentage of formula for each diet fed to red tilapia

Table 2. Average weight gain, average growth rate per day and survival rate of red tilapia feed experimental diets

During the experiment no mortality had occurred. This might be supported by a good water quality where water temperature ranged from 25 to 29°C, dissolved oxygen was 4.05 to 6.75 ppm, ammonia was 0.15 to 0.42 ppm and pH was 6.3 to 7.5.

REFERENCES

Almazan, J.G., R.G.V. Pullin, A.F. Angeles, T.A. Manalo, R.A. Agbayani, T.B. Trono. 1986 Azolla pinnata as a dietary component for Nile tilapia, Oreochromis niloticus. Proc. of the First Asian Fisheries Forum, Manila, Philippines. p. 523–528.

Anonymous. 1988 Fisheries Statistics of Indonesia. Directorate General of Fisheries. Department of Agriculture. Indonesia. p. 75.

Edward, P. 1980 Food potential of aquatic macro-phytes. ICLARM Studies and Review 5. Manila, Philippines. p. 51.

Jauncey, K. and B. Ross. 1982 A guide to tilapia feeds and feeding. Institute of Aquaculture. University of Stirling. Scotland. p. 111.

Maria, K. 1988 The feeding effect of Azolla (Azolla pinnata), Lemna (Lemna sp.) and its combination to growth rate of grass carp (Ctenopharyngodon idella C.V.). Thesis. Bogor Agricultural University. Bogor. p. 43. (In Indonesian).

Milner, M., D.I.C. Wang and Scrimshaw. 1978 Protein resources and technology: Status and research need. AVI Publishing Company, Inc. West-port Connecticut. p. 503–520.

Winarno, F.G. and A. Rahman. 1974 Protein and its roles. Department of Agricultural and Food Technology. Fatemeta. Bogor Agricultural University. Bogor. p. 85. (In Indonesian).

Figure 1. The growth curves of red tilapia fed with five kinds of experiment diet

Appendix 1
THE PERCENTAGE OF NUTRIENT FOR EACH DIET FED TO RED TILAPIA

Appendix 2
THE PERCENTAGE OF NUTRIENT FOR EACH FERMENTED INGREDIENT

SOME ASPECTS OF THE USE AND MANUFACTURE
OF FORMULATED FISH FEEDS

by

Kwan Foo Seong
Chee Kheng Stock-Feeds Mfg. Co., Ltd.¹

1. INTRODUCTION

Fish and shrimp production, like other forms of livestock production is a function of several independent variables, among which are feed quality and quantity, feeding frequency, stocking rate, stocking size, time and temperature. In extensive and integrated forms of aquaculture, the success of such operations depends on the ability of the farmer to circumvent the need to use formulated fish feeds. These operations employ low stocking rates, some form of non-specific feed like ricebran, copra cake, even agricultural/animal wastes, plus organisms which the cultured species could capture from its environment. As long as production is low, such a system can operate with a reasonable chance of success.

However, the use of non-specific food is inefficient in utilization of human and land resources and results are to a certain degree, unpredictable and unreliable, because culturists must depend on many factors beyond their control.

With the intensification of production, the farmer immediately encounters the problems of supplying an adequate quantity of properly formulated feed presented in a manner suitable and acceptable to the animal. The contribution by natural food will be proportionately less in such an environment, and hence the manufactured feed must contain all the nutrients, both macro- and micro-nutrients, at the levels known to be essential for maximum growth at lowest cost. Therefore, intensive culture of fish and shrimp depends on feed, and of all the functions relating to production, feed quality and quantity are probably the most important. Assuming that this feed is consumed and the nutrients in it are available and assimilated without causing a stress to the animal, we can say that there is no production without feed.

2. TYPES OF FEED

Fish feeds can be classified as wet, dry or mixed depending on the quantity of moisture contained in it. Wet feeds are simply mash mixed with a certain amount of water. Natural wet feeds are obtained from the water environment and are vital food sources in extensive culture systems. Dry feeds generally entail fewer storage and handling problems to the farmer than high moisture feeds.

At the present stage of development in feed technology, live feeds are still necessary for feeding very young fish and shrimp, and rotifer, moina and artemia are cultured for such purpose.

¹ Chee Kheng Stock-Feeds Mfg., Co., Ltd., 2400 MK-1 Tingkat Perusahaan 2, Prai Industrial Complex, PW Penang Malaysia

Note: The views expressed in this paper are those of the author and do not necessarily reflect the views of FAO.

Catfish fry (Clarias macrocephalus) are still given moina for the first 30 days. According to Tan (1988), 18 cigarette tins of wet moina are required to feed 10 000 catfish fry for the first 21 days. At the cost of $2.50 per tin from the moina farm, the cost of feeding 10 000 fry to weaning is $45.00. The survival of the fry was better than 90 percent. However, this statement needs clarification. The broodstock were able to produce gametes equal to 20 percent of their own body weight. The gametes had excellent batching rates (>95 percent) and subsequent survival. The breeding fish were kept in aquarium tanks and their only source of nutrients came from a feed containing 32 percent protein. Freshly captured females from the wild are unlikely to produce gametes of such quantity and quality because of their uncertain nutrition.

Some hatcheries use tubifex worms and Artemia with success. Tubifex worms are, however, uncertain in quality because they may have been collected from environments with polluted water.

Trash fish, if available, is an important food for cultured species, and is used on a large scale. Due to its high moisture content, about 7 kilos of trash fish are required to produce 1 kilo of siakap (seabass) and catfish. The price per kilo of trash fish varies from 15 cents in Lumut to 35 cents in Kukup and hence the feeding cost of 1 kilo of siakap varies from $1.05 in Lumut to $2.45 in Kukup without accounting for mortality. The quantity of dry matter in trash fish varies from 17 percent to 25 percent depending on the size and species of trash fish. This means that the dry matter of trash fish required to produce 1 kilo of siakap is about 1.2–1.8 kilos. To be attractive for the farmer to use, trash fish must be cheap because use of this material involves much handling and storage problems either to the farmer or to the supplier of trash fish. Trash fish and fish by-products would be better if heated to deactivate thiaminase, or thiamin supplementation is necessary.

The difficulty of feeding a carnivorous species like siakap with artificial feed can be overcome by the use of wet feeds. Early attempts to feed carnivorous species met with difficulties and wet feeds which could be mixed with trash fish and slaughter-house by-products, were found to be readily acceptable to such fish like eels which were difficult to train to eat dry feeds.

Manufactured moist feeds are still used on a large scale in some countries, but trucks specially equipped with cold storage facilities are necessary. However, the wet feed can be simply prepared on-farm by blending manufactured feed in mash form with water and trash fish, and the resulting dough can be fed directly to cultured fish. Ghittino, (1979) reported that moist diets can induce diseases such as kidney diseases, nocardiosis and ichthyophoniasis. Generally, fish fed with wet diets have lower organoleptic properties, the meat is less consistent and contains higher fat levels. On the other hand, dry diets can also induce fish diseases such as hepatoma when they contain aflatoxin, nephrocalcinosis and granulomatosis, but research in progress indicates the possible prevention of such dietic diseases.

Dry feeds, because of their obvious advantages of convenience, flexibility in manufacture and ready availability in any quantity will be increasingly used in feeding fish. The development and use have greatly influenced culture and management techniques leading to high stocking density and automatic feeding.

Dry feeds can be made as mash, pellets or crumbles. The pellets can be made in various sizes to suit the needs of fishes of different sizes. A substantial portion of the formulation is still fish meal, although literature review shows that the fish meal can be replaced by suitable substitutes like soybean oil meal (Viola, et. al., 1982) and other substitutes (Greenland, et. al., 1984), without sacrificing much in performance parameters if the amino acid profile and energy level are re-balanced. The carbohydrate portion can be from maize, rice or wheat, while soybean oil meal and ground nut meal are imported sources of protein. In addition, micro-nutrients like vitamins and trace minerals can be added in very precise quantities.

Therefore, depending on needs, dry feeds can be made as complete feeds, protein and/or energy supplements. The feed can be supplied in bulk, bags of 50 kilos or less, and their keeping qualities can be improved by the use of anti-oxidants and anti-mould agents. Storage presents no problems, and any rat-free, fairly dry room with good air movement can be used to store the feed.

3. PRODUCTION CAPACITY AND NEEDS

Any feedmill equipped with pelleting facilities is in a position to produce fish pellets without much modification other than to install another hammermill screen for finer grinding, and perhaps addition of a second mill for double grinding.

In 1984, the production of freshwater fish amounted to 11 900 tonnes comprising mainly of carps, gouramy, tilapia and the freshwater fish. Marine cage culture produced 800 tonnes of seabass, grouper and the mangrove snapper, while the shrimp industry produced 600 tonnes of tiger shrimp (Ubaidillah, 1985). From our knowledge of the production of freshwater fish, the apparent feed conversions have been 1.3 for cage cultured tilapia in mining pools, 1.8 for catfish in ponds, and up to 2.4 for tilapia and catfish cultured in tanks on the same feed. We cannot state that the tilapia and catfish cultured in various sites and under various systems were homogeneous population, but we have obtained similar results from three years of observations. Therefore, we can say with some degree of confidence that at most 19 000 tonnes of fish feed would be sufficient to feed all the freshwater fish in the country, provided that all the fish are given only feed! Pond results show apparent feed conversions of 2.3 for the tiger shrimp, and a good feed for the seabass under cage culture would be expected to give efficient efficiencies of 2.2. Therefore, we would need 1 800 tonnes of feed for the marine fish and 1 400 tonnes of feed for the shrimp. The total feed for aquaculture species calculated in this arbitrary way would amount to 22 000 tonnes per year or 71 tonnes daily.

At least eight feedmills in the country can produce this quantity of fish mash in four hours, and one or two could produce this quantity in less than two hours. Producing the fish feed as pellets would need an easy eight-hour day. The only bottleneck in the manufacture would be the need to grind the feed finely. An additional cost factor due to operations would be the greater processing loss involved. Since only a small amount of fish feed is actually used by farmers, local mills have the capacity to meet the needs of the aquaculture industry for a long time to come.

The exception is the production of floating feeds, the use of which is justified as an aid to management. It is a great advantage to be able to see whether fish have been given adequate quantities of feed, and a floating feed enables the farmer to assess the growth and condition of his fish.

4. FLOATING FEEDS

The manufacture of floating feed involves the use of fairly high levels of carbohydrates expanded during the extrusion process. The feed, when freshly made, appears foamy, and the net result is that the density is reduced. There is also a degree of gelatinization of the starch leading to improved digestibility. Flour from rice, corn and wheat make good carbohydrate material for the extrusion process. Live steam, pressure and heat are produced as a result of this process, and bacteria and salmonella are destroyed. Consequently, the shelf life of the product is enhanced.

The production cost is higher, and an imported floating feed containing 28 percent protein is available in the country for about $1.30 per kilo. Due to a requirement for higher starch levels in the formula, there is a disadvantage of lower flexibility in feed formulation.

From a review of literature available, the extruded pellet appears to be nutritionally no better than the ordinary pelleted feed of the same formula. Hilton, et al., (1981) noted that the extruded pellet was more durable, had superior water stability and absorbed more water than the pellet made from the same formula. However, rainbow trout fed the ordinary pellet gained significantly more than the fish fed the extruded pellet but had lower feed efficiency after 13 weeks of feeding. MgBenka and Lovel (1984) fed channel catfish on an all extruded diet to satiation daily, while other groups of catfish were given equal weights of the same feed as pellets, or 45 percent pellets and 55 percent extruded pellets. They found no significant differences in growth, feed conversion, body composition or size variation among the treatments. The decision to use extruded or normally pelleted feeds must be based on management needs rather than on nutritional reasons, at least for the time being. However, there may be a case for using extruded feeds for shrimp because of its better durability and water stability, but this decision must be balanced against higher feed costs.

Floating feeds have been found to be acceptable to carnivorous fish like seabass. To compete against trash fish, the floating feed must cost less than $1.40 per kilo and give an efficiency of not more than 1.8. The production cost would then be less than $2.52 per kilo of fish. We can be fairly certain that such a feed might be acceptable to farmers in Kukup, but will be rejected in Lumut.

5. CONSTRAINTS TO FEED DEVELOPMENT

The machinery required for the manufacture of a floating feed is very expensive. Dry extruders are cheaper. The demand for fish feed is too small to justify the installation of extruders for their production. Some feedmills have installed extruders, but not for the production of fish feeds. Attempts by importers to introduce floating feeds to siakap farmers have met with failure possibly because the feeds were too highly priced to be acceptable.

The production of shrimp feeds also faces similar problems of a small and dispersed market. Feedmills, for greater economy, are constructed to operate on a large scale. The minimum batch size for many mills is 2 tonnes and the capacity is often 20–40 tonnes per hour. In most cases, the pelleting and cooling sections of a feedmill cannot even operate smoothly unless there are at least 2–4 tonnes of pellets in the system. Clearly, it is not economical for feedmills to produce large quantities of aquaculture feeds when the demand is very small. Feeds are perishable materials, and under the prevailing conditions of high humidity, feed will deteriorate quickly. The storage should not exceed seven days and feed must be used quickly.

There is no doubt, however, that use of aquaculture feeds will expand, but this will probably take a little more time.

Other constraints facing the feedmills are the lack of precise data on the nutritional requirements of local fishes, and the possible shortage of certain ingredients leading to high prices.

The physical requirements for a good aquaculture feed are by now, well known and there is no need to discuss factors like pellet durability, water stability, etc. When producing aquaculture feeds, the nutritionist is faced by a bewildering array of species, some omnivorous while some are carnivorous, with different diet preferences and feeding habits. The feedmill nutritionist has to interpret research findings and apply nutrition concepts according to the ingredients he uses. He will always try to formulate for best growth and feed efficiency bearing in mind that concepts and findings in nutrition are always applied in the most economical way. Even then, any feed after being formulated and well processed, may not be used in the way the nutritionist has planned, because other factors like pond fertility and usage rates are not under his control.

Our field observations show that the local catfish, can achieve the same final weight in the time on either a feed with 32 percent protein or 24 percent protein. However, with a 32 percent feed, farmers use a level of 2.5 percent, while on the 24 percent feed, they use a level of 6 percent based on catfish biomass. The final feed efficiencies are 1.8 for the 32 percent and 2.4 feed for the 24 percent feed. Personally, it is felt that 6 percent of the fish biomass is too high to feed, and it is doubtful if the fish can consume this quantity. Our own tank experiments showed that catfish and tilapia cannot finish feed given at 6 percent of the fish biomass. Water pollution occurred and fish growth was retarded. Some farmers cannot accept that feed should be given at 1 to 2.5 percent of fish biomass.

Management expertise differs in different farms. Some farmers stock catfish at 120 000/ha at starting size of 1-inch and get a final survival rate of only 30 percent. Another, much wiser, will stock 50 000/ha with a starting rate of 2.5 inches, and gets a final survival rate in excess of 70 percent. A stocking policy could define the best pond and stocking conditions so that all involved in aquaculture can expect to obtain uniform and comparable results as in the poultry industry, but formulation of such a policy will be difficult because of differing pond conditions.

Even if formulated by computer, two feeds do not always give the same level of production. The computer does not distinguish feed ingredients quality unless the operator programmes certain ingredients into the formula. Also, the computer programme does not allow for the nutritional effects of increasing quantities of a given ingredient and calculations are based on the assumption that effects are linear.

Lastly, the supply of quality raw materials for aquaculture feed may present a problem in one or two cases on a temporary basis. Materials used for manufacturing feeds are fish meal, soybean meal, ground nut meal, rice, corn, wheat, ricebran, corn gluten, wheat gluten, squid and shrimp waste meal.

The supply of fish meal is affected by the monsoon and during such seasons, fish meal is poor in quality and price is high. The supply of squid meal and shrimp waste meal is always poor, although they may not be necessary in feeds for the catfish and tilapia. Some large corporations are now beginning to process poultry on a large scale, and hopefully, the resulting feathers and by-product will be rendered to produce hydrolysed feather and poultry by-product meals which can replace fish meal in the feed.

Corn gluten and wheat gluten are byproducts of the cereal industries and are usually imported from Europe. Again it is hoped that corn gluten will be produced by a Penang-based company which is processing corn for sugars. The country produces large quantities of palm kernal meal, but our work shows that at levels above 15 percent in the diet, growth rate of the tilapia is depressed (Unpublished data).

Aquaculture feeds generally contain high levels of protein compared with those feeds for terrestrial farm animals, and so high protein materials are used in aquaculture feeds. As has been shown in the country many year ago, further research may lead to formulation for aquaculture feeds with lower protein in the future, resulting in more efficient feeding.

6. SOME QUALITY CONSIDERATIONS

It is not difficult to monitor the quality of any given feed. The chemical properties can be measured by proximate analysis in the laboratory to ensure that the feed has met the specifications. Growth and feed utilization are useful biological parameters to observe, although the interpretation of feed conversion data can mislead many. The quality of a feed is dependent on the quality raw materials used in its manufacture. For example, fish meal may become damaged during storage due to the presence of highly reactive fat, and lysine availability can drop nearly 20 percent compared with the undamaged meal.

The presence of toxins is always a problem in feed manufacture. The most common is aflatoxin which can contaminate almost any material used in the feed, and very often the feed itself. In two experiments, corn that had been contaminated by aflatoxin B1 was incorporated into fish feed at various levels, so that the feed contained graded levels of aflatoxin B1. This feed was given to tilapia and catfish fingerlings. The tilapia fingerlings suffered almost 100 percent mortality and the catfish only slightly less when the feed contained less than 30 ppb of aflatoxin B1, a level generally regarded as safe (Unpublished data).

Two feeds with the same protein levels may not give the same performance, nor do they cost the same. This is an effect of ingredient quality. Therefore, the real economic growth worth of a feed is not the price of feed per kilo, but the monetary worth of the fish produced by a unit, say a dollar worth of the feed.

In general, low protein high moisture and bulky feeds can be regarded as feeds of low quality. They involve more transport and handling, and may also put a stress on the environment and/or the fish.

Finally, the farmer may decide to carry out on-farm mixing of feed. Costs of on-farm mixing are often under-estimated because farmers usually do not put a price on their own management time and analysis costs. If costs are realistically calculated, and the farmer can obtain quality ingredients, there is no reason why fish feed cannot be produced on-farm.

REFERENCES

Ghittino, P. 1979 Formulation and technology of moist feeds. In Proc. World Symp. Finfish Nutrition and Fish-feed Tech. Hamburg, 20–23 June 1978. Vol. II. pp. 37–40.

Greenland, D.C., H.K. Dupree and C.H. Long. 1984 Growth, studies conducted on channel catfish fed diets with fish meal or fish meal substitute. Feedstuffs, 56:20.

Hilton, J.W., C.Y. Cho and S.J. Slinger. 1981 Effects of extrusion processing and steam pelleting on pellet durability, pellet water absorption and the physiological response of rainbow trout (Salmo gairdmeri R.). Aquaculture, 25:185-194.

MgBenka, B.O. and R.T. Lovell. 1984 Feeding combinations of extruded and pelleted diets to channel catfish in ponds. Prog. Fish. Cult. 46: 245–248.

Tan, E.S.P. 1988 Pers. Comm.

Ubaidillah, Abdul Kadir. 1985 Strategi dan Program Pembangunan Akuakultur. Persidangan Akuakultur, 9–12 Dec. 1985. Johor Baru.

Viola, S., S. Mokady, U. Rappaport and Y. Arieli. 1982 Partial and complete replacement of fish meal by soybean meal in feeds for intensive culture of carps. Aquaculture, 26:223-236.

THE AVAILABILITY OF FORMULATED FEEDS, THEIR MANUFACTURE AND
FEED CONVERSION VALUES FOUND IN WEST MALAYSIA

by

S. Pathmasothy¹ and Lim Teck Jin

1. INTRODUCTION

Freshwater fish culture has been gradually gaining popularity as indicated by the increasing number of fishponds and farms as well as by the increasing demand for fish seeds. It is even expected to further develop in the coming years mainly due to the aggressive developmental stand now being pursued by the Department of Fisheries, Malaysia. As the industry grows, the demand for fish feed will simultaneously increase as shown by the livestock industry where feedmilling industry developed in parallel with the development of the swine and poultry industry. A similar pattern of development is at present taking place in the cattle industry where these animals are being fed formulated concentrates instead of forage only.

Similarly in the area of freshwater fish culture we are at present in an identical transition phase where farmers are shifting from the traditional extensive system of culture depending on just pond fertilization to semi-intensive system requiring supplementary feeding and some totally intensive culture requiring complete feed. Although there are about 11 500 fish farmers in the country at present, there are still no reliable figures indicating the number of farmers involved in the various types of culture but general observations indicate that a majority of the farmers practice semi-intensive culture where some kind of supplementary feeds are given. A list of the commonly utilized supplementary feeds are presented in Table 1. Wherever large fish farms are developed on a commercial scale, utilization of formulated feeds is common and can be safely said to be prerequisite to the viability of that project.

¹ Staff, Freshwater Fish Research Centre, Melaka

Table 1. List of the commonly utilized supplementary feeds in West Malaysia

* All values expressed in terms of percentage of dry weight.

In the year 1986, the total surface area of freshwater ponds stood at 2 594.3 ha along with 1 296 ha of tin mining pools and another 8 101 sq m under cage culture, (Annual Fisheries Statistics, 1986). If one is to use just the acreage of ponds under culture with the assumption that under normal culture practice one would obtain about 2 to 3 mt/ha of fish with a feed conversion of 2, then the total feed that would have been utilized in that year would have amounted to about 10 000 to 15 000 mt of fish feed. Similarly the net production of all freshwater fishes for the year 1986 was 4 709 mt and on assuming that it was cultured with formulated feeds with a feed conversion of 2, then the amount of feed utilized in the particular year would have been about 9 418 mt. Although these figures are based on partial acreage and on certain assumptions and not including the fact that not all freshwater fishes feed on supplementary or formulated feed, we can, however, safely say that there is a need for locally produced fish feeds.

2. NUTRITIONAL REQUIREMENTS OF WARMWATER FISHES

The practice of intensive culture resulting in the nullification of any contribution by the rich natural feeds in the pond has placed a demand for data on the nutritional requirements of warmwater fishes the major requirements for proper feed formulation. The response from the fish nutritionist have been good, however, there are some large variations in the optimal requirements such as in the case of proteins the major ingredient in feed. However, the general requirements of protein for most warmwater fishes can be safely said to be in the range of 28 to 36 percent crude protein in production diets and even higher in the case of frys and fingerlings which may require as high as 45 percent. Some of the research findings of the various workers are presented in Table 2. Production diets of carps have a lipid content of 10 to 15 percent (NRC, 1977) but levels as low as 6 percent have resulted in good growth. Similarly research is under progress to determine not only the amount of lipid need at various stages of growth but also on the type and percentage of fatty acids needed. Less attention has been paid to carbohydrates, for fish do not utilize this source as efficiently as protein or lipid but is said to have protein sparing effect and in certain cases helps in protein digestion (Ufodike, 1983). More work has been done on vitamins than on mineral requirements but the consensus of most workers is that the requirements laid down by the National Research Council on Nutrient Requirement of Warmwater Fishes can be utilized as a suitable guide. Thus, with the various data available at present the local feedmillers in this country can successfully formulate feeds for freshwater fishes which can result in feed conversion values of two and below.

Table 2. Protein requirements of some freshwater fishes

3. STATUS OF MANUFACTURING FISH FEED

Commercial feedmilling in Malaysia started about some 30 years ago in parallel with the development of the swine and poultry industry which at present is the major industry for the supply of edible protein. Thus, one can confidently say that the local feedmilling industry has the ability and capability to produce high quality feeds. Similarly, one can safely conclude that the availability of the raw ingredients for the manufacture of fish feed is not a problem even though most of the raw ingredients are imported. For example, Malaysia imported about 1.4 million mt of animal feedstuff in the year 1985 (Babjee, 1987). A list of the commonly utilized raw ingredients are presented in Table 3.

Table 3. A list of the commonly available raw ingredients utilized in fish feeds

* Adapted from Devendra, 1979

Although the 65 or so feedmillers can formulate a pellet high quality feed to meet the nutritional requirements of the fish, the end product, however, does not meet the physical requirements that is long term water stability and integrity of the pellet. Certain feedmillers even do not attempt to produce pellets of uniform length. Water stability is a prerequisite for all fish feeds both in dry and wet form. Most feedmillers today have their machinery geared towards the efficient production of dry pellets which are ideal for land animals. Thus, these feeds with very low water stability although nutritionally satisfactory, on contact with water will immediately start to disintegrate resulting in it becoming a high quality fertilizer rather than feed. Observations have shown that a 24 percent crude protein pellet with long term stability produce higher production in culture ponds rather than a 32 percent crude protein pellet with very low water stability. This indicates that water stability is a very important factor to be considered and is the major constraint in the production of local feeds.

This critical problem can be overcome by either adding binders or by utilizing extruders rather than the conventional pelleting machine. Both of these two steps will result in a higher cost of production. This fact should be accepted by all and what has to be studied now is how to keep this extra cost to a minimum during the production of long term water stable pellet. If the cost of the pellet is very high, most farmers will not purchase it unless it is profitable which depend on the feed conversion and selling price of the fish. Fish with a high price may be cultured economically but generally most cultured freshwater fishes do not fetch a high price compared to prawns and shrimps. But unlike prawn and shrimp feed which require pellets with hours of water stability, fish pellets need to be water stable for at least 5 minutes but longer periods are more desirable especially when the feed is utilized by a farmer with no fish culture experience. One method of reducing the cost of binders is to incorporate raw ingredients in the feed formulation which have nutritional value as well as binding properties. Examples of such materials are fish solubles, dried whey, wheat middlings, wheat gluten and wheat flour (Chua and Teng, 1980; New 1986). These and other similar materials when subjected to fine grinding and steam pelleting results in partial gelatinization of the starches which helps to bind the feed to make it sufficient. Similar raw ingredients in feed mixtures when passed through an extruder which cooks the feed under higher temperature and pressure results in pellets with very long term water stability, which can also be made to float if required. In this process a greater degree of gelatinization of the dietary starch place, thus increasing the bio-availability of the carbohydrate which in turn may also have better protein sparing effect (Hilton, et al., 1981). It may be due to this reason that some feedmillers producing extruded feed tend to reduce the protein content in their feed. Finally, the pellets can also be coated with oil to increase their stability.

4. AVAILABILITY OF FORMULATED FISH FEEDS

Only recently can a local fish farmer purchase some fish feed in small quantities, that is about 100 to 200 kg at a time. In the past most feedmillers insist that one has to procure this specially prepared in bulk that is 1 to 2 tons at a time which is totally not viable to small farmers. This amount is said to be the filling capacity per run in large feedmills. However, some feedmillers are not appointing agents to do the selling in small quantities. This slow and cautious attitude of the local feedmillers to invest in extruders has forced the farmers to purchase floating feed that are imported. Today, these imported floating feeds are easily available throughout the country.

5. FEED CONVERSION EFFICIENCY OF LOCAL FEEDS

Feed conversion values are a very valuable guide to gauge the quality of a particular feed. At the Batu Berendam Freshwater Fish Research Station, our aim is to produce feeds that can provide a feed conversion of below 2.0 in all tank and pond culture systems. This does not, however, mean that feeds having feed conversion of greater than two are not encouraged. The acceptability of such feed will depend on cost of the feed. Some of the feed conversion values attained at the station experimental tanks and ponds are presented in Table 4.

It is important to emphasize here that before one can comment on any feed conversion value one has to consider a large number of other parameters other than feed alone. For example, in the hands of inexperienced farmers even the best feed will result in poor feed conversion. Other parameters which affect feed conversion are as follows:

1. Water quality parameters such as pH, temperature, dissolved oxygen, ammonia and turbidity all affect feed consumption.

2. Biomass of the fish, heavy stocking in static ponds may affect water quality via accumulation of metabolites which influences feeding and growth rate.

3. Sex and strain of the fish. In certain species males and females have different growth rate. Oreochromis niloticus male have a growth rate of 1.7 times that of the female and even greater when the female starts to breed. Breeding activities also affect feed consumption. Certain strains due to inbreeding may not have good growth rates and hence influences feed conversion.

4. Management of feeding that is feeding regime, frequency and schedule. Excess feeding will not only affect feed conversion directly but also indirectly by affecting the quality of the pond water. In certain species feeding twice a day has better results than once a day. Fishes trained to feed at fixed times everyday respond by being present at the feeding area which makes feeding efficient.

Table 4. Some feed conversion values obtained with local feeds in tank and pond culture trials

¹ Pathmasothy and Lim, in press
² Pathmasothy and Lim, 1987
³ Pathmasothy and Omar, 1982
⁴ Pathmasothy and Omar, 1982
⁵ Pathmasothy and Lim, 1988

Observations have shown that farmers who understand the above factors are the ones who have attained good feed conversion values and only their data can be utilized by both the feedmillers and fish nutritionists. In conclusion, at present some of the feeds produced in this country have a feed conversion of below 2 and with improvement in the water stability of the pellet more farmers will be able to achieve this target.

ACKNOWLEDGMENTS

The authors would like to acknowledge the Director General of Fisheries and the Head of the Batu Berendam Fisheries Station for their support in the field of fish nutrition.

REFERENCES

Aizam, Z.A., S.G. Ross and H.A. Sharr. 1983 Growth of Ikan Patin, Pangasius sutchi, fingerlings fed with varying dietary protein levels. Pertanika, 6(2):49–54.

Babjee, A.M., 1987 Animal feed industry in Malaysia. Proc. 10th Ann. Conf. MSAP. pp. 1–13.

Chua, T.E. and S.K. Teng. 1980 Economic production of estuary groupers, Epinephelus salmoides, reared in floating cages. Aquaculture, 27(3):273–283.

Cruz, E.M. and I.L. Laudencia. 1978 Preliminary study on the protein requirements of Nile tilapia (Tilapia nilotica) fingerlings. Fish. Res. J. Philipp., 3(2):34–38.

Dabrowski, K. 1977 Protein requirement of the grass carp fry Ctenopharyngodon idella Val. Aquaculture, 12:63–73.

Davis, A.T. and R.R. Stickey. 1978 Growth responses of Tilapia area to dietary protein quality and quantity. Trans. Am. Fish. Soc., 107(3): 479–493.

Devendra, C. 1979 Malaysian feedstuffs (Mardi), Serdang, Selangor.

Hilton, J.W., C.Y. Cho and S.J. Slinger. 1981 Effect of extrusion processing and steam pelleting diets on pellet durability, pellet water absorption and the physiological response of rainbow trout (Salmo gairdneri. Aquaculture, 25:185–194.

Jauncy, K. 1982 The effect of varying protein level on the growth, food conversion, protein utilization and body composition of juvenile tilapias (Sarotherodon mossambicus). Aquaculture, 27:43–54.

New, M.B. 1986 Aquaculture diets of postlarval marine fish of the super-family Percoidae, with special reference to seabass, sea bream, groupers and yellowtail. A review. Kuwait Bull. of Marine Sc. (7):75–148.

Ogino, C. and K. Saito. 1970 Protein nutrition of fish. I. The utilization of dietary protein by carp. Bull. Jpn. Soc. Sci. Fish., 36:250–254.

Pathmasothy, S. and R. Omar. 1982 The effect of four different diets on the growth of Leptobarbus hovenii. MARDI Res. Bull., 10(1):110–113.

Pathmasothy, S. and R. Omar. 1982 Growth performance of Leptobarbus hovenii fingerlings fed isocaloric diets with variable protein levels. MARDI Res. Bull. 10(3):418–424.

Pathmasothy, S. and T.J. Lim. 1987 Effect of feeding virginiamycin on the growth rate, feed conversion and carcass composition of Pangasius sutchi (Fowler). Proc. 10th Ann. Conf. MSAP. pp. 197–200.

Pathmasothy, S. and T.J. Lim. 1987 Comparative study of the growth rate and carcass composition of the striped catfish, Pangasius sutchi (Fowler) fed with chicken viscera and pelleted feeds in static ponds. Fish. Bull. No. 50.

Pathmasothy, S. and T.J. Lim. 1988 The response of Pangasius sutchi (Fowler) fingerlings fed on isocaloric diet with variable protein levels. In press. Malaysian Agri. Journal.

Pathmasothy, S. and T.J. Lim. 1988 The culture of all male, all female and mixed populations of Nile tilapia, Oreochromis (Sarotherodon) niloticus (Family cichlidae) in static ponds. Presented at the Fisheries Research Seminar, 28–29 June 1988.

Teshima, S., G.M.O. Gonzalez and A. Kanazawa. 1979 Nutritional requirements of tilapia: Utilization of dietary protein by Tilapia zillii. Mem. Fac. Fish. Kagoshima Univ., 27(1):49–57.

Ufodike, E.B.C. and A.J. Matty. 1983 Growth responses and nutrient digestibility in mirror carp (Cyprinus carpio) fed different levels of cassava and rice. Aquaculture, 31:41–50.