GCP/CAF/007/NET Field Document 2 June 1984

by

K.W. Chow
Fish Feed Technologist

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 1984

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TABLE OF CONTENTS

1. INTRODUCTION

2. SUMMARY AND RECOMMENDATIONS

2.1 Feeds and Feed Formulation

2.1.1 Feed requirement
2.1.2 Ingredient supply
2.1.3 Ingredient quality
2.1.4 Feed formulation
2.1.5 General conclusions on feed ingredient supply and feed formulation and recommendations

2.2 Diet-Making Machinery and Equipment

2.2.1 State of existing machinery
2.2.2 Repairs and upgrading made on machinery
2.2.3 Recommended purchase of spare parts
2.2.4 Equipment fabrication
2.2.5 Recommended purchase of additional diet manufacturing equipment

2.3 Feeding Trials for Clarias Culture in 1984

2.3.1 Comparative feeding trials
2.3.2 Biculture of Clarias and Tilapia (pond)
2.3.3 Extensive culture involving compost

LIST OF FIGURES

1. Parts of a steam cooker for moist, pelleted feed manufacture

2. Schematic and experimental design for extensive polyculture of Clarias and Tilapia

1. INTRODUCTION

The Hatchery Production and Research Centre at Bangui-Landjia Project was established in 1980 under the FAO/Government Cooperative Programme (GCP/CAF/007/NET) with funds provided by the Government of the Netherlands.

The project is engaged primarily in work on the African catfish (Clarias lazera), although activities outside the hatchery building itself include pond experiments and small-scale commercial production of Clarias and tilapia in polyculture.

Because catfish culture generally requires artificial feeding, these experiments are important in determining the technical and economic feasibility for commercial production of the species, using feeds made from a rather limited selection of local ingredients.

The need to process compound feeds arises from the desire for diets with high water stability in order to prevent feed wastage and to control fish disease. Feed processing equipment purchased earlier under the FAO project Vulgarisation de la Pisciculture et Autofinancement des Stations Piscicoles Principales (CAF/80/002), referred to in this report as the other FAO project, are employed in making all feeds presently required for the project.

As part of the operation of the project, FAO assigned Dr K. W. Chow, Fish Feed Technologist, Aquaculture Development and Coordination Programme, as a consultant to the project. This report summarizes the consultant's findings made during the period 7 to 17 November, 1983, concerning the supply of feed ingredients to meet both present and future needs of the station and the state of existing feed manufacturing machinery and their need for repairs and upgrading. It also includes a brief description of repairs carried out on the machinery during the period, construction of equipment for moist, pelleted feed production, and discussions with Mr J. A. L. Janssen, FAO Fish Culture Expert on the project, concerning his work plan for 1984.

2. SUMMARY AND RECOMMENDATIONS

2.1 FEEDS AND FEED FORMULATION

2.1.1 Feed requirement

Feed requirement for the project is presently estimated at about 50 t/ year. The requirement of the other FAO project, mainly for poultry and pig diets, is a little over 40/t. Total requirement for feeds, therefore, is about 90 t/year. While fish diets weigh heavily on high-protein feed supplements, diets for pigs and poultry place more emphasis on feed grains and other high-energy feed ingredients. At present, these needs are met by locally available maize, oilseed cakes, brewery waste products and slaughter house waste products (principally blood meal).

2.1.2 Ingredient supply

During the past year, two events adversely affected the supply of feed ingredients to the station. The first was the closure of the only flour mill in the country due to a change in government policy concerning import duties on wheat and wheat flour. This closure effectively dried up supplies of wheat bran and pollard to the station. Secondly, rainfall during the first half of the year had been much less than usual, resulting in a very poor rice crop. Consequently, the supply of rice bran had been very much reduced. At the time of the consultant's visit, rice bran was no more available.

With the loss of supplies of rice bran and wheat milling by products, there is greater reliance on maize as the chief energy feed. The supply of this ingredient, too, has been affected by newly created demand for it by a new brewery that came into operation during the past year. As a result, the price of maize has risen by almost 50 percent.

A list of available ingredients appear in the following table:

A note of interest is the currently lower price for oilseed cakes compared with maize. Notable also is the rather high cost of vitamin supplements (constituting almost 15 percent of the total cost of a typical formulation used at the present time).

2.1.3. Ingredient quality

An inspection of the ingredients currently used at the station shows that oilcakes in general, because of the expeller process employed for oil extraction, are high in residual fat content and prone to rancidity under the tropical conditions. Levels of natural toxins such as gossypol in cottonseed cakes and aflatoxins in groundnut cakes have not been ascertained. This knowledge is important because of the high level of usage of these items. Samples of the ingredients will be sent to Holland for assay of these toxins. The local maize is of the waxy variety. Waxy starch is not as easily digested as non-waxy starch by simple stomach farm animals. Unfortunately, no information on this exists for fish. Local blood meal has a rather inconsistent quality, often with highly fluctuating bone content. The presence or absence of salmonella (a common contaminant of meat by-products) has also not been ascertained.

2.1.4 Feed formulation

Formulation of compound feed for Clarias culture at the station has been dictated more by ingredient availability than by the need to meet precise, known, nutrient requirements of the species. Mr Janssen has a good grasp of feed formulation concepts. A typical formulation for Clarias fingerlings that has been producing fairly good response consisted of: cottonseed cake, groundnut cake, maize, brewery waste (dried), blood meal, dicalcium phosphate and vitamin and trace mineral supplements.

Because of the changed situation in feed ingredient availability, as already mentioned in Section 2.1.2, this consultant has recommended a partial switch to moist pellet production. The following is the composition of a binary-type test diet that was formulated and prepared on 14 November 1983.

¹ Used as a mould retardant

The “wet” and “dry” groups of components were mixed separately. The mixed “wet” components were steamed for 30 minutes in a container specially fabricated for this purpose (see Section 2.2 on Diet Making Machinery and Equipment). The result was a moist cake which was then blended into the “dry” mixture, with a further addition of 4 litres of cold water.

Steaming the “wet” components gelatinized starch that was present in the mixture to give the latter the sticky consistency which was desirable for producing a water stable end product.

Moist pellets produced from the above formulation, while water-stable after sun drying, broke up fairly rapidly when placed fresh in water. This is because of the high proportion of coarse, fibrous brewery waste in the mixture and the nature of starch present in the local maize variety.

A second formulation in which wet brewer's yeast was substituted for part of the brewery waste and maize gave better results. Semi-dry pellets from this formulation remained stable in water for more than two hours.

A return of supplies of rice bran, better yet wheat bran, in the future, will enable the production of stable moist pellets, because cooked rice starch is more “sticky” than waxy maize starch.

2.1.5 General conclusions on feed ingredient supply and feed formulation and recommendation.

While nothing can be done to alter the feed ingredient situation, certain remedial actions can be immediately taken to optimize the use of available ingredients and to bring down the cost of feed compounded at the station.

From a purely economic standpoint, a critical feed supply situation occurs only when feed production cannot continue because essential ingredients become unavailable and no substitutes are found, or when the high cost of ingredients make production of fish by intensive feeding, uneconomical. Under this definition, fish production by intensive feeding in Bangui is still highly profitable, principally because of high value of the product in the local market. The situation may change, however, if there is unexpected cut-off of supply of imported oilcakes from Chad, or rapid rise of ingredient prices due to greater demand.

To prepare the station for this eventuality, this consultant recommends the greater utilization of brewery waste by turning to alternative processing methods of compound fish feeds. This method (of moist pellet manufacture) will be discussed further in a later section. Another immediate action recommended to reduce cost is to find alternative supplies of less-expensive micro ingredients. Vitamin supplements normally constitute less than 5 percent of the total ingredient cost in compound feeds. At present, this is up to 15 percent. Use of more concentrated forms of vitamin supplements can reduce this cost.

Present high levels of usage of maize in all diets at the station is due to such diets being prepared in the dry form. High cost maize and the availability of fairly large quantities of cheap wet waste from the local breweries make a change in feed formulation strategy desirable. The introduction of moist pellet production for Clarias and wet mash for pigs makes this switch possible.

2.2 DIET-MAKING MACHINERY AND EQUIPMENT

2.2.1 State of existing machinery

Pellet mill

The California Laboratory Pellet Mill presently used at the station is about ten years old. For some time before the start of the Clarias project, it was in disrepair and disuse. According to Mr Janssen, before it could be recommissioned three years ago, the electrical control had to be rewired because of the burnt-out main circuit breaker. The rewiring that was carried out simply linked the main power supply directly to the motor starters. This, therefore, caused the ammeter for the main water to be bypassed. Without an ammeter to monitor electrical power consumption and without protection of circuit breakers, the mill had to be operated at below optimum capacity to prevent main motor burnout.

Inspection of mill components indicated many worn parts. The drive chain of the feeder was broken and temporarily held together by a wire. This made it impossible to increase the rate of feed entering the pellet chamber. The feeder control handle was also broken and was held in place by another wire. Two of the four screws that held the roller in place in the pelleting chamber were also broken.

Operation of the mill under the above conditions resulted in production far below capacity, estimated at 25 kg/h, compared with the equipment manufacturer's specification of at least 75 kg small diameter pellets per hour.

Grinder

The 5 HP full-screen grinder is a fixed-hammer type impact grinder. Output of this machine was also far below expected levels, at less than 50 kg/h through a screen size of 2.5 mm. The reasons for the low capacity were: (a) motor-drive belt slippage. The flat-type drive belt is worn and loose, and there is less than full transmission of power from the motor to the grinder, especially under increasing load; (b) worn edges of the hammers. The efficiency of grinding declines steeply as the angular edges of the hammers of such grinders become worn or rounded. Production was also affected by underloading for fear of motor burnout because of the absence of an ammeter to monitor current consumption.

Mixer

For Clarias diets, mixing was done by hand on the floor. An improvised hand-power horizontal drum mixer made from a 200-litre oil barrel was used for mixing feed for pigs and poultry.

2.2.2 Repairs and upgrading made on machinery

Pellet mill

(a) Ammeter

The main-motor ammeter was reinstalled by this consultant. Although no new circuit breaker was available, the now functional ammeter permits safe use of the mill at full power (at 3 amps as indicated on the ammeter).

(b) Roller

The broken roller screws were extracted at a local workshop and new screws found to replace them.

(c) Drive chain and control

The wire holding the two ends of the drive chain was replaced temporarily by a more proper link obtained from another chain. Although not quite the correct size; this link permits operation of the feeder at a higher speed.

A new drive control arm of the feeder was fabricated at a local machine shop according to a design provided by this consultant. The installation of this arm will ensure more steady feeding of feed mix into the pelleting chamber.

With the above repairs carried out, production was very much speeded up (almost doubled).

Grinder

(a) Ammeter

An ammeter was purchased and installed to monitor current load. Maximum load should give a reading of 6 amps. Due to belt slippage, this has not yet been achieved.

(b) Hammers

Hammers were replaced for more efficient grinding.

(c) Drive belt

Specifications were given to a local workshop to provide new pulleys and belts to convert the transmission system from flat-belt to V-belt drive.

Until the new transmission system is in place, capacity is not expected to increase significantly due to slippage. However, when installed, the new transmission should make possible grinding capacity of 150–250 kg/h, depending on screen size.

Mixer

Specifications have been recommended to Mr Mievis for his drum mixer to improve its efficiency and to cut down on the time required for each mixing cycle. These modifications include, basically, the welding of vanes in a certain pattern to the inner wall of the drum.

2.2.3 Recommended purchase of spare parts

Pellet mill

The following is a list of spare parts compiled by Mr Janssen and the consultant for immediate purchase from CPM in Holland.

Spare Parts List

2.2.4 Equipment fabrication

The mass production of moist pellets required specially made equipment. Designs for steam cooking diet mixtures were provided to the station's mechanic who fabricated a large steam cooker from a steel oil drum, angle irons and round steel bars used in building construction, and wire netting (Fig. 1).

2.2.5 Recommended purchase of additional diet manufacturing equipment

The following purchases of equipment are recommended to upgrade the diet manufacturing capability of the station:

1. Vertical, fountain-type, mixer of 250 kg capacity.

2. Hobart-type, mixer-mincer for moist diet mixing and extrusion.

2.3 FEEDING TRIALS FOR CLARIAS CULTURE IN 1984

An active work programme has been planned for 1984 involving comparative feeding trials and testing of different systems of culture.

	Lid for Cooker
	Made from scrap metal sheet
	Basket
	Made from round steel bars and wire netting
	Stand for Basket
	Made from round steel bars
	Cooker
	Made from bottom-half of 200-litre oil drum
	Stand for Cooker
	Made from angle irons and round steel bars

Fig. 1 Parts of a steam cooker for moist, pelleted feed manufacture

2.3.1 Comparative feeding trials

Larval Diets: Hatchery

An experiment will compare the efficacy of the following diets for Clarias larvae:

• decapsulated artemia
• hatched artemia
• freezedried micro-encapsulated whole egg diet
• mixed zooplankton (fresh)
• a commercial diet preparation of mixed zooplankton of German origin

Fingerling Diets: Hatchery

An experiment to compare two levels of animal protein (blood meal) and three mixtures of oilseed cakes (cottonseed and groundnut cakes).

Fingerling Diets: Ponds

As above.

2.3.2 Biculture of Clarias and tilapia (pond)

Experiments to compare four stocking densities (10, 20, 40, 80 fish/m²) and four stocking ratios of the two species.

2.3.3 Extensive culture involving compost

This consultant has suggested a test to determine the possibility of increasing the effectiveness of a compost system by increasing the perimeter to surface area ratio of a compost heap.

The experiment will involve two perimeter/area ratios (one five times the other) and two stocking densities, three and six fish/m², in biculture with tilapia (see Fig. 2).

Comment on Disease affecting Clarias

At the time of the visit there was a serious outbreak of disease among Clarias fingerlings in the hatchery. The disease symptoms were quite typical. Lacerations were found on the posterior end of the fish and the dorsal fins in most cases were rotted away. This disease appears also to afflict other Clarias species and has been blamed for massive fish losses in Thailand.

When a slide preparation was made by Mr Janssen from scrapings from affected fingerlings, two things were very evident. Not only were myxobacteria found in abundance, the slides also showed even heavier infestation of saphrophytic fungi. The hyphae of these parasitic fungi were scattered all over the entire field of the slide.

Although the etiology of this common disease afflicting Clarias has not been determined, this consultant hypothesized that primary body lesions are caused by the hyphae of the parasitic fungi. The fungi probably are first produced from spores (found in natural water supplies in warm climates) attached to food remnants. These remnants then get lodged in the fin webs of the fish and the hyphae of the fungi attack the adjoining skin surfaces. Once open wounds are produced, proliferation of myxobacteria occurs as a secondary infection. The best means of preventing the disease is to prevent overfeeding and to include a mould retardant in the feed.

Recommended Compost

Large Perimeter

Fig. 2 Schematic and experimental design for extensive polyculture of Clarias and Tilapia

Stocking Ratio: Tilapia (T) to Clarias (C)

Stocking Density: No. fish/m²