FAO/UNDP FISH NUTRITION AND AQUACULTURE DIETS PROJECT
THA/89/003

By

Hassanai Kongkeo

DRAFT

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Table of Contents

Terms of Reference

Itinerary

Persons Met

Organization of Research Programmes on Shrimp Feed Management

Organization of Training/Demonstration Programmes on Shrimp Feed Management

Training Manual for Shrimp Feed Management

Development of Economized Marine Shrimp Feed

Development of Economized Marine Finfinish Feed

Other Duties

Recommendations

I. TERMS OF REFERENCE

The Term of Reference for the two-month consultancy of a Fish Feed Technologist was to assist the Project in:

• organizing research and training/demonstration programmes in shrimp feed management

• developing economized marine shrimp and finfish feeds

II. ITINERARY

III. PERSONS MET

Dr. Plodprasop Suraswadi
Director General, Department of Fisheries

Mr. Somsak Singholka
Deputy Director General, DOF

Ms. Bung-orn Saisithi
Deputy Director General, DOF

Dr. Kitjar Jaiyen
Director, National Inland Fisheries Institute

Mr. Prasert Sitasit
National Project Manager, THA/89/003

Dr. Mali Boonyaratpalin
Senior Nutritionist
National Institute of Coastal Aquaculture, Songkhla

Ms. Nanthiya Unprasert
Nutritionist, NIFI

Mr. Pairat Kosutaruk
Nutritionist, NIFI

Ms. Benjaluck Lertbhuddhikul
Administrative Assistant, THA/89/003

Mr. Thienthong Uvetvatana
Director, Surat Thani Inland Fisheries Research and Development Centre

Mr. Anuwat Ratanachote
Chief, Surat Thani Brackishwater Fisheries Station

Mr. Singha Chansawang
Manager, Kanchanadit Shrimp Farming Co-operative
Surat Thani

Mr. Hong Suthitanakom
Namchai Shrimp Farm, Klongkone
Samutsongkhram

Mr. Donchuen Ruangsung
Kula Thong Farm, Tahsala
Nakorn Srithamrat

Mr. Somchai Klinkachorn
SPK Farm, Klang
Rayong

Mr. Michael B. New
Coordinator, EEC/ASEAN/ADCP, Bangkok

Mr. Imre Csavas
Regional Aquaculture Officer, RAPA Bangkok

IV. ORGANIZATION OF RESEARCH PROGRAMMES ON SHRIMP FEED MANAGEMENT

Research activities on shrimp feed management should be generally carried out at the farm sites in order to keep the environmental condition as close to that of actual farming as possible. At present, there are five specific sites being selected for testing of marine shrimp feed formulae and feed manufacturing machinery, as follows: Kanchanadit Shrimp Farming Cooperative. Surat Thani; Surat Thani Brackishwater Fisheries Station. Surat Thani; Kulathong Farm, Nakorn Srithamrat; Namchai Shrimp Farm, Samutsongkhram; and SPK Farm, Rayong. To make it less expensive for the Government to operate, four of these are private/cooperative farms. The private sector can play an important role on these research activities by providing all or sharing in the provision of facilities, expenses and labour. The project designs the experiments and follows them up as frequently as is feasible. For emergency cases, the project should be contacted by long distance phone. It was found that assigning one project staff to each farm was not possible due to the insufficient number of institute staff. These farms have their own feed manufacturing machines designed by the project. So that it is more convenient for the project to develop a scheme of cooperation with the farms/stations for research implementation. The number of grow-out ponds in each farm (except the government-operated Surat Thani BFS) varied from 10 to 30. The culture system for cooperative and government farms is semi-intensive while those of private farms are both intensive and semi-intensive.

The main research activities on feed management necessary for the project at this stage of development are as follows:

1. Research on feeding rate of each project shrimp feed formula with different stocking densities and providing tables for estimated daily feed allotment. The feeding rate at different stocking densities are slightly different depending on the availability of natural food per biomass and quality of feed. At the beginning of the experiment, the general feeding rates with different stocking density, as recommended in the training manual, may be used. After allowing at least 3 experimental crops to re-adjust the feeding rate and obtain the optimum feeding rate, the result should be attached to the given formulae for the information of the farmers. According to the complicated calculation of quantity of daily feed utilization based on feeding rate for small-scale farmers, the guideline for daily feed allotment should be also given to the farmers.

2. The comparison of feed conversion ratio and economics between project, commercial, and combined feeds. In general, there are four sizes of marine shrimp feed with different protein levels. The economics of feed manufacturing at the farm site of all sizes of feed are determined by the size of the farm; the large farm can produce feed economically due to a higher on-farm demand. Normally the biggest size of feed is always economical due to the large amount consumed during the last two months. However, it is still doubtful if the demand of small-scale farms for small size feed can be high enough for machine capacity. Therefore the feed production costs of each size should be studied carefully. If it is not economical, the small sizes of commercial feeds or fresh feed should be used by the farmers during the first two months. The experimental ponds for economic studies of shrimp production costs, should be set up as follows: two ponds feeding with all sizes of project feeds; two ponds feeding with all sizes of best commercial feeds; two ponds feeding a combination of small size commercial feeds and big size project feed; and two ponds feeding at the first two months with fresh feed and at the last two months with big size project feed.

3. The result of bottom condition of the ponds fed by project feed. The economized formulae sometimes cause more problem on remnant feed due to its low cost ingredients and attractants. The symptoms of polluted pond bottom will not significantly appear during the first crop. The decomposed remnant feed will accumulate and affect survival of shrimp in later crops. Therefore, the pond bottom of three continuous crops should be investigated before introduction of feed formulae to the farmers. Most of the toxic gases produced by decomposed remnant feed generally covered by siltation layer which can not be detected by water sampling. Since shrimp have the habit of searching for food by digging the pond bottom and burying into it, a high level of toxic gases in the pond bottom can be exposed and directly harm the shrimp. The level of toxic gases (ammonia, hydrogen sulfide and methane) in bottom soil should be sampled regularly twice a month.

4. The suitable ratio of mixed feed between project feed and supplementary feed, like trash fish, acetes, clam and mussel, for semi-intensive culture. If the stocking density of shrimp in the pond is less than 5 pieces/m2, such small amount of artificial feed given can not be searched by shrimp. Later those feed will be covered by siltation to create bottom pollution. Hence, it is necessary to supplement with fresh feed to increase the weight of feed give daily so that it can be searched by shrimp. In general, the conversion rate of fresh feed to dry feed is 4:1. The percentage of supplementary feed should be gradually decreased following the increase in feed consumption as shrimp become larger. This is to limit the amount of fresh feed so as not to pollute the pond. The experimental semi-intensive ponds in Surat Thani Brackishwater Fisheries Station or Kanchanadit Shrimp Farming Co-operative should be set up to find the proper ratio of supplementary feed at the different scales of stocking density in semi-intensive culture. This ratio will be directly beneficial to small-scale farmers.

V. ORGANIZATION OF TRAINING/DEMONSTRATION PROGRAMMES ON SHRIMP FEED MANAGEMENT

The local training programme on marine shrimp feed for 50 DOF officers and 50 intensive farmers was scheduled to be held in Bangkok in June 1990. The objectives of this four day training/demonstration course are to train the government extensionists (for further training of local farmers) and intensive farmers on relevant technical information about shrimp feed, methodology of local feed production, and feed management programme. This course will be co-organized and funded by the Fishery Extension Division. The project will be responsible for arrangement of course schedule, lecturers, laboratory work, and field work. The topics of the lecture, laboratory and field work sessions are recommended as follows:

Lecture (at NIFI Bangkok)

• Introduction of shrimp feed
• Feeding habits of shrimp
• Types of shrimp feed
• Nutrient requirements of shrimp
• Main feed ingredients
• Feed additives and binders
• Physical forms of feed
• Recommended shrimp feed formulae
• Feed machinery or equipment
• Methods of feed manufacture
• Economics of feed production

• Feed management *:

  • feed storage
  • selection criteria for shrimp feed
  • feeding management
  • pond preparation
  • water management
  • diseases which affect feeding
  • records of feed management

Laboratory (at NIFI Bangkok)

• Feed analysis
• Feed production

Field Work (at SPK Farm, Rayong)

• Feed management *
• Feed production

(*) = Consultant volunteers to give lecture and practical training on this topic

The other level of training/demonstration course on marine shrimp feed is for 50–100 semi-intensive farmers at Kanchanadit shrimp Farming Co-operative, Surat Thani and other farmers in the south of Thailand, during July or August 1990. This two-day course will be organized by the project and funded by the cooperative. The subject matter for the lectures and for practical demonstration will be as follows:

Lecture (at Siam Thani Hotel. Surat Thani)

• Introduction to shrimp feed
• Feeding habits of shrimp
• Composition of ingredient
• Recommended feed formulae
• Feed machinery
• Supplementary feeding for semi-intensive culture *
• Feed management for semi-intensive culture *

Demonstration (at Co-operative farm)

• Feed machinery
• Method of feed manufacture
• Feed management for semi-intensive culture *

(*) = Consultant volunteers to give lecture and demonstration on these tropics

VI. TRAINING MANUAL ON SHRIMP FEED MANAGEMENT

This training manual is prepared by the consultant for use in the DOF Officers and farmers training/demonstration courses on Marine Shrimp Feed which will be held in 1990. It will also serve as a guideline for DOF extensionists in training farmers. The contents of this manual are as follows:

Feed management is the most critical factor for profitability of shrimp farms, especially intensive culture. Normally, artificial feed will be used only for intensive culture because in such stocking density, natural food is not enough and feeding by fresh feed will cause pond pollution. Artificial feeds are expensive and comprise from 50–70% of the total variable cost of production. Therefore, feed quality and feed management are critical for profitability of shrimp farm.

1. Feed Storage

Artificial pellet feeds require special care during storage to prevent deterioration in quality. Stock control is also necessary to enable the farmers to fulfill the feed needs of shrimp adequately but not in excess. Stocking period recommended by the feed producers should be strictly followed. The following are the major factors which affect the quality and weight of feedstuffs during storage :

• scavenging animals, particularly rats and cats
• high level of moisture which always causes insect infestation, acceleration of the growth of fungi, the destruction of its physical structure and water stability
• heat generated by both environment and the growth of fungi and insects which may reduce the availability of amino acids and vitamin in feed
• infestation by insects, such as ants, moths, weevils and beetles which cause damage through weight loss and the exposure of the feed to further damage by fungi, oxidation, and contaminating bacteria
• growth of fungi which always causes weight loss, increase in temperature and moisture, off-flavour, discolouration and production of aflatoxins
• enzymatic actions and the development of oxidative rancidity of lipids

Artificial feed should be used as quickly as possible in tropical conditions. General recommendations for storage of artificial feeds are given as follows:

• ensure that the storage area is water proof
• storage room should be dry, cool and provided with good ventilation
• all entry points should be meshed to prevent entry of scavenging animals
• ensure that the feed delivered from feed factory is always new
• keep the store clean
• arrange good inventory system to ensure that the oldest is used first
• raise the sacks off the ground by stacking them on wooden platforms to prevent insect damage. To ensure good ventilation between the feed bags, each stack should be not more than 5 bags high
• if there is a sign of insect infestation, apply insecticide (opened sacks should be firmly tied to prevent contaminating the feed with the chemical)
• do not walk on the stacks of feeds unnecessarily
• leave a space between the stacks and the wall
• do not leave the feed sack open
• the maximum storage period for each batch should be two months in tropical countries (this also depends on quality of feed) or three months from the time of processing; feed should not be left under direct sunlight to prevent spoilage of feed by temperature change at night

2. Selection Criteria for Shrimp Feed

The major criteria for selection of shrimp feed in intensive culture are the following: cost-effectiveness of feed (i.e. the cheapest feed that can adequately supply nutrient requirement). attractiveness to the shrimp, efficiency of the feed conversion ratio, and stability in water to prevent feed loss and minimize water pollution. Due to the slow feeding behavior of shrimp and the high cost of feed, the pellet stability in water and buoyancy are important factors to minimize the loss of nutrients. The acceptable level of pellet stability is less than 10% loss in original weight upon immersion in water for 10 minutes. Shrimp feed need to be water-stable for a minimum of 2 hours. It could last for 12 hours without changing in shape, which shall be wholly eaten by shrimp. However, optimum water stability also depends on the frequency of feeding times per day (the more feeding times the less optimum water stability). The good feed should not contaminate the water quality or cause dregs to sink to the pond bottom.

There are approximately 40 essential nutrients which are believed to be required by shrimp. The nutrient levels used for feed manufacturing may be less than this if the natural foods are enriched. The major nutrient requirements for shrimp feed are as follows:

• Protein (shrimp size 0–0.5, 0.5–3.0, 3.0–15.0 and 15.0–40.0 gm. require protein levels at 45, 40, 38 and 36 % respectively)

• Lipid (shrimp size 0–0.5, 0.5–3.0, 3.0–15.0 and 15.0–40.0 gm. require lipids levels at 7.5, 6.7, 6.3 and 6.0 % respectively)

• Fibre levels should not exceed 4% (a minimum level of 0.5 % Chitin for molting in shrimp feeds, is recommended)

• Ash levels which refer to the inorganic element or minerals, should not exceed 18% (recommended levels of Calcium, Phosphorus, Magnesium, Sodium, and Potassium are 2.8, 1.8, 0.2, 0.6 and 0.9%, respectively)

• Attractants such as fish solubles, should be generally at levels of 1–5 % (if shrimp are observed to be fondling pellets then dropping them without eating, the feed may not have adequate flavor). All efficient attractants could have leached out of the feed within 1 to 1.5 hours)

• Vitamins at the following recommended levels

  Thiamin	150	mg/kg of feed
  Riboflavin	100	"           "
  Pyridoxine	50	"           "
  Pantothenic acid	100	"           "
  Niacin	300	"           "
  Biotin	1	"           "
  Inositol	300	"           "
  Choline	400	"           "
  Folic acid	20	"           "
  Ascorbic acid (Vitamin C)	1,200	"           "
  Vitamin A	15,000	IU/kg of feed
  Vitamin D	7,500	"           "
  Vitamin E	400	mg/kg of feed
  Vitamin K	20	"           "

• Binders such as wheat gluten, alpha starch, gelatin. collagen, agar etc., are utilized to increase water stability (amount of binders depend on processing technology and ingredient particle sizes)

The size of feed pellet should be small enough to be carried to the mouth and to enable shrimp to carry the pellet while swimming. However, it should be large enough to be water stable and to prevent the feed from passing through the screen during water exchange. The recommended pellet sizes for 0–3, 3–15 and 15–40 gm. shrimp are 1 mm (crumble), 2 mm × 4 mm, and 2.5 mm × 5 mm.

Shrimp feed should not contain large particles of ingredient which causes uneven distribution of nutrients in the feed. Colour variation of pellet also indicates inadequate mixing of ingredient and a variation in cooking of feed during processing. Pale colour of feed will indicate over-cooking which could destroy proteins and vitamins while dark colour indicates under-cooking which could result in poor water stability. Variation in feed pellet texture and any fractures on feed, caused by poor processing, will reduce water stability.

There are many factors that affect the feed efficiency of shrimp, for example: pond water quality, water temperature, pH, salinity, turbidity, natural food, diseases, toxic substances, feed management, culture methods, etc. Hence it is difficult to identify which FCR is the selection criteria for shrimp feed. The FCR for a good feed should ideally be 1.5–2.0.

The maximum moisture content of pellet should not exceed 10% to prevent the destruction of water stability and feed texture as well as insect infestation and acceleration of fungus growth.

The above selection criteria may not be convenient for small scale farmers. Hence, it may be more convenient for farmers to use known good feeds from reputable manufacturers, in combination with some of the above guideline which can be identified, as selection criteria. Though the good feeds are more expensive they would give excellent results i.e. better FCR, good growth and less water pollution.

3. Feeding

Feed consumption of shrimp generally relates to the size of shrimp, water and substrate quality, weather conditions (e.g. sunny or cloudy day), and physiological conditions (e.g. molting, diseases). Underfeeding of shrimp can result in growth variation and lower survival rate as a result of molted shrimp being eaten by strong ones. Overfeeding will increase feed cost and cause pond pollution by feed waste, followed by diseases. Therefore it is important to ensure the proper amount of feed given to shrimp every meal. Feeding rates of shrimp will not stay steady throughout the crop.

Due to slow eating habit of shrimp, it is recommended to feed more frequently with smaller quantities to prevent wastage and the loss of soluble nutrients. Though the feed manufacturers can produce extremely water stable feed with high cost binder, these feed can be too hard for shrimp digestion and may not be as palatable as softer feeds. If the feeds stay too long at the pond bottom, they will be covered by siltation causing loss of attraction and thereby adding to the wastage. Frequent feeding also results in more uniform sized shrimp. Shrimp are nocturnal and continuously intermittent feeders. Therefore, the major portion of the daily feed allotment should be administered at night when shrimp are most active (e.g. 0600 hrs = 20%, 1200 hrs = 20%, 1800 hrs = 25% and 2200 hrs = 35%). With highly intensive circular ponds where shrimp are forced by water movement to be active throughout the day, the amount of feed per meal should be almost similar.

To yield the best production with the lowest feed cost, artificial shrimp feeds should be managed following these steps:

3.1 Follow Recommended Feeding Guides. At the initial stage, the farmers should follow the recommended feeding guide given by the feed manufacturers. Most of these feeding rates and frequency will fall into the following ranges:

The daily quantity of feed can be calculated by the following formula.

Daily feed quantity = estimated number of shrimp × average shrimp weight × percent of feeding rate (following the above guide)

During the first two months, it is impossible to accurately estimate both number and weight of shrimp in the pond by the cast nets because shrimp are too small to be caught by big-mesh cast nets. The only reliable method to estimate shrimp weight is to weigh the shrimp collected from feed inspecting trays. In general, big shrimp will enter the tray first and always keep the smaller shrimp away from the tray. The smaller shrimp have a chance to enter the tray only later. Therefore, sampling should be done every 15 minutes for 1.5 hours from initial feeding. Survival rate or number of shrimp in the pond can be obtained only by the given fixed rate (e.g. 1^st week = 98%, 2^nd week = 96%, 3^rd week = 94%, 4^th week = 92%, 5^th week = 88%, 6^th week = 86%, 7^th week = 84% and 8^th week = 82%). Though the calculated daily feed quantity on the first two months is not accurate, the daily amount of feed is too little to cause pollution of pond water or feed waste.

After two months, sampling by cast nets for both average weight and survival rate becomes more accurate. For common practice, the mesh size of cast net is 1 cm × 1 cm in which 7.0 cm or 2.5 gm shrimp can be trapped. Shrimp sampling should be done at 15- day intervals at 8 or 10 different spots. These spots should not be repeated in the next sampling. It is recommended to avoid casting in the afternoon as well as during molting period to prevent shrimp from suffering temperature shock. The results of sampling during flooding the pond will not be accurate because most of the shrimp will crowd at the water gate. The number of shrimp per m² can be calculated by the number per catch divided by the area of fully open cast net.

For small-scale farmers who would have difficulty with this complicated calculation, the guidelines for estimated feed allotment are given in Table 1, 2, 3, 4 and 5. These feed allotment are based on a 1-ha pond which can be easily converted to the actual size of farmers ponds.

Table 1. Estimated daily feed allotment for stocking density of 10/m² in 1-ha pond

Table 2. Estimated daily feed allotment for shrimp stocking density of 20/m² in 1-ha pond

Table 3. Estimated daily feed allotment for shrimp stocking density of 30/m² in 1-ha pond

Table 4. Estimated daily feed allotment for shrimp stocking density of 40/m² in 1-ha pond

Table 5. Estimated daily feed allotment for shrimp stocking density of 50/m² in 1-ha pond

For old shrimp farms, the above feeding guides can be replaced by the past feeding records of the good production crops. The past feeding records are more accurate in estimation of feed consumption because the pond and environmental conditions are almost similar.

In Thailand, stocking of PL15 fry is a more common practice than stocking of nursed fry. At this stage of larvae, they can not easily search for the limited amount of pellet given. Therefore plankton are the main feed for them. It is more convenient for the shrimp farm with water storage pond/reservoir where phytoplankton can be cultured in advance. During the first month, poultry manure or chemical fertilizer (15–15–15) is applied weekly at the rate of 150 kg/ha or 30 kg/ha, respectively, to the reservoir at a water level of 1.5 m. If there is no reservoir, shrimp pond should be fertilized in advance before stocking with poultry manure at the rate of 60 kg/ha or chemical fertilizer at 12–15 kg/ha. Water level in the pond is maintained at 30 cm for 3–4 days depending on light duration and light intensity. When the water becomes brownish-green, the water level is raised to 80 cm and the pond is now ready for stocking. An experienced farmer can visualize the water colour and turbidity due to phytoplankton mass. The simple method is by using a white disc submerged in the water. If at the depth of 20–40 cm, the disc is still visible, plankton density is optimum.

If the pond can not be fertilized on time, application of artemia nauplii at the rate of one can (350 gm) daily during the first week is recommended. It is also recommended not to further fertilize the culture pond after stocking as the lab-lab will occur quite often. It is very difficult to eliminate the floating lab-lab without shrimp fry because they will accumulate under lab-lab. To sort the small fry from lab-lab by hand is nearly impossible.

Shrimp farms in Thailand are usually located close to the seawater supplies so that water pumping is convenient. Thai farmers also realize the need for maximum rate of water exchange to eliminate the problems of pond pollution, diseases and the stagnant growth. The maximum exchange of full-salinity seawater sometimes causes the lack of natural food such as phyto-and zooplankton. The phytoplanktons are essential to the shrimp in its early stages and necessary for the growth of zooplankton and benthic organism, which serve as supplementary feed for shrimp at adult stages. Therefore, it is recommended to give other supplementary feed in addition to pellet feed for the pond with clear water. Trash fish, clam, mussel and acetes do not only enhance the growth of shrimp but also harden and enhance the colouration of the shell. The blue shell is commonly caused by a deficiency in carotenoid which is a component of Vitamin A. In the pond, shrimp can utilize carotenoid from both artificial feed, fresh feed, green and brown phytopklankton. It has been observed that the blue shell symptom occurs during shortage of phytoplankton in the pond. Vitamin A in artificial feed alone is insufficient. Powdered shrimp shell or head can also be mixed into the feed at the ratio of 1:5 to boost the carotenoid content of the ration. Release of live krill from other sources into the pond having such problem may be another solution.

Intensive culture of larger size shrimp (15–20 pieces per kg) that fetch a better price, is not usually practised in many countries. The growth of shrimp generally stunts at 30 pieces per kg due to the shortage of natural food when the biomass per m2 goes over 700 gm. This can be easily observed by the ability to produce larger size shrimp in extensive pond. To cross this barrier, a sufficient amount of plankton produced in reservoir is regularly supplied to the pond in conjuction with supplementary feed of pellet by fresh feed. The stocking density should be kept at 15/m2. The ponds (both rectangular and round) are equipped with a central drainage system for continuous removal of feed wastes caused by excess amount of fresh feed. Within 5 months the shrimp could grow further to 15–20 pcs/kg size for a total yield of 6–8 tons/ha. The farm-gate price of shrimp this size is twice that of 30 pcs/kg.

The recommended supplementary feed are shown in the following table:

* the conversion rate of fresh feed to dry feed is 4:1

The above formula is used for ponds equipped with central drainage system. For the ordinary sluice gates in which the water exchange is not as efficient as the central drainage system, the supplementary feed should be given only during the first and last months to prevent pond pollution.

3.2 Feeding Methods. Feed should be spread over the pond area to avoid accumulation at certain places. This can minimize wastage and pond bottom deterioration. At present, the proper method of feeding in Thailand is by hand because labour is cost effective and the operation is more delicate than other methods. The amount of feed broadcast manually can be easily adjusted to suit the areas in the pond where shrimp population are different. For example, shrimp will be more crowded at the inlet gate than the outlet gate. Feed consumption of shrimp for each meal is irregular, therefore it is very complicated to re-adjust frequently the feeding devices of automatic feeding machines. Feed sprayer installed on the truck or tractor, could get stuck during rainy season. Feeding by trays placed at definite areas on the pond, is also not suitable because feed can not be broadcast. The small shrimp can not compete with the big ones in limited area of feeding tray, so that the small ones become even smaller due to malnutrition. With the shrimp's slow eating habit, the big shrimps would stay in the tray at least half an hour.

For a pond larger than 0.5 ha, broadcasting the feed by hand along the dike can not make the feed available at the centre of the pond. It would be necessary to bring them to the centre by boat or by use of a feeding cannon.

3.3 Monitoring of Feed Consumption. A simple method to check whether the feed given is insufficient or in surplus quantity, is by the use of feed inspecting trays. This tray is made of 1.0 × 1.0 m2 mosquito net lifted by bamboo handle. Generally, these trays are sunk at 40 m interval along the pond dikes or approximately one tray per 1000 m2. The amount of feed kept in a net is one teaspoonful for every kilogram of feed broadcast into the pond. Two hours after feeding, the tray is slowly lifted to inspect whether it contains remnant feed. This complicated calculation for the quantity of feed given in the tray may not be suitable for small-scale farmers. Therefore they could more conveniently use the method of fixed quantity of feed given and adjust the checking period. The amount of feed is fixed at one coffee cup per net while the checking period of 1st, 2nd, 3rd and 4th months are 2.0, 1.5, 1.0 and 0.5 hours, respectively.

If there is remnant feed in the tray, decrease the ration by 5% in, subsequent feeding time. However, if all the feed is consumed and some shrimp are stranded in the tray, increase the amount of feed by 5% on the next meal. Normally, shrimp will molt once every 6–8 days in higher temperature and once every 15 days in lower temperature. The feed consumption will decrease a lot at one or two days before molting, meanwhile it will sharply increase more than 100% after molting. Therefore this monitoring should be done every meal for close management of feeding. If it is possible to check the molting shrimp in the tray, the amount of feed may be subsequently increased by 20 % instead of 5 % for the next meal.

The feed inspection trays are also useful for observation of predators. If predators comprise more than 20 % of total population in tray, tea seed cake should be applied. For this application, the water level should be lowered to 50 cm to minimize the quantity of tea seed cake. Dissolved tea seed cake at the rate of 180–250 kg/ha is applied into the pond. Allow two hours before beginning to let in the maximum water supply. The large volume of water exchange also stimulates shrimp molting which is an advantage.

Every 15 days, the amount of feed given will be confirmed by the sampling of shrimp with cast nets, as earlier mentioned. It is also recommended to check the pond bottom twice a month by diving to take samples of bottom material. If the sample contains black stuff and smelling of hydrogen sulfide, this indicates that a large surplus amount of feed is being given. An excessive amount of such bottom material requires immediate removal by waste sucker. However, one has to be careful in operating this locally made machine because it can stir up the waste and excite the shrimp. Removal should be done in the morning when water temperature is not high to avoid temperature shock to the shrimp. It has to be slowly dragged to prevent the dispersion of hydrogen sulfide into the water.

4. Pond Preparation

After harvest of the previous crop, the pond has to be drained thoroughly. Some ponds may have seepage from underground water sources; this water should be continuously pumped out. Pond bottom is thoroughly treated with dissolved lime at the rate of 200–300 kg/ha and left to be sundried for at least 3 weeks until the soil surface cracks.

If the bottom had been fouled from the previous crop or the pond had been used for several crops, the bottom normally contains several toxic gases as follows:

1. Hydrogen sulfide (H₂S) This is formed due to anaerobic bacterial reaction (heterotrophic bacterial metabolism) on leftover feed and precipitated death plankton which are generally composed of S-containing amino acids and ester sulfide. A 1.3 ppm concentration can cause shock, paralysis and eventually death to shrimp.

2. Ammonia (NH₃) This is produced from the excretion of shrimp, decomposition of leftover feed and accumulation of other organic materials with bacterial reaction. Besides being toxic directly to shrimp, ammonia influences water pH and suppresses the growth of phytoplankton. The lethal concentration of ammonia in the pond water is 1.6 ppm.

3. Methane (CH₄) At anaerobic condition, fatty acid from the leftover feed could be decomposed by bacteria becoming methane gas.

Most of the gases produced will be covered by siltation layers. Therefore it is difficult to be detected by water sampling. A high level of toxic gases in the pond bottom can be harmful by direct contact to shrimp since shrimp has a behaviour of searching for food at the bottom or burying into the bottom. Pond treatment with lime alone can not eliminate these gases when the fouled layers of the pond bottom are over 3 cm. The remedy for this problem is to spray lime solution at the beginning as indicated previously, after the water is completely drained. This is followed by tilling over the entire pond bottom by hand or a small tractor. Tilling is aimed at oxidization of Hydrogen sulfide (2 H₂S + 3 O₂ → 2 H₂O + 2 SO₂) and evaporation of Ammonia and Methane. If the fouled layer is over 5 cm thick, a big tractor should be used to remove the filth from the bottom onto the dikes while the good soil from the dikes can be used for replacing the pond bottom. In areas where water is turbid, the rate of siltation is high which can gradually make the pond shallower. By scraping out the top layer of the pond bottom, the usual depth is still maintained without dumping good soil from other sources.

Besides eliminating the bacteria that produce the toxic gases, liming can also satisfactorily kill other pathogenic bacteria, viruses and predators such as mollusc, crabs and fish. It prevents acidity as well.

After allowing the tilled pond to dry for three weeks, it is flushed with water to wash away the residual lime and gases. The water supply should be screened to prevent entry of predators. Some predators like crab, sea snake, sand gobi and tilapia, could not be easily killed by piscicides because they can bury or remain in the crevices or holes. Completely drying the pond with long exposure to sunlight effectively eradicates them. After flushing, the pond is filled with water to a depth of 30 cm. Tea seed cake is applied at the rate of 150 kg/ha or dry rotenone at 90–130 kg/ha to ensure total elimination of predators prior to larval stocking.

5 Water Management

The most common problem resulting from over-feeding is the build up of anaerobic conditions to generate toxic gases. Excess feed also acts as a fertilizer that can induce an over-bloom of phytoplankton to reduce dissolved oxygen level in the water at night. If water quality is impaired by excess feeding, it is necessary to flush the pond immediately and as much as possible to reduce the plankton density and remove toxicity.

For super-intensive culture in round ponds where the continuous circular movement of water by aerators (12 paddle wheels or Aire-O₂) will cause the accumulation of the wastes at the centre of the pond, the wastes can be easily drained through a central drain device under the pond. The velocity of water current also causes the slow sinking of the feed to the bottom, therefore the bottom is always clean. Though the stocking rates are as high as 50–100 per m2, the good water circulation system always keeps the pond clean.

Water exchange is generally a means to mitigate all problem including diseases, over-blooming of phytoplankton, oxygen level, carbon dioxide level, pH, toxic gases, etc. The daily water exchange schedules are recommended as follows:

During the first week after larval stocking, water exchange is not commonly practiced to allow maximum phytoplankton blooming. At this stage there is little pond waste to cause pond deterioration. Rate of water exchange can be altered occasionally depending on plankton density, high salinity, infected shrimp, acidity, etc. A precautionary measure during water exchange is to screen efficiently the incoming water to prevent entry of predators and competitors. If a reservoir is available, the grow-out pond can be gradually stocked during the day; screening of a slow rate of water flow using the finest mesh is more efficient.

6 Diseases Which Affect Feeding

There are many diseases caused by excessively filthy pond bottom and poor water quality. The ability of infected shrimp to consume feed is reduced. If the farmers still keep feeding at regular amount, accumulation rate of remnant feed is sharply increased. This does not only cause shrimp stress but also lowers their resistance to other pathogens that abound in the water or on the pond bottom. Therefore high mortality of shrimp will be additionally caused by deterioration of pond. The best treatment and preventive measure is to maintain good water condition and pond bottom. If shrimp are observed to be inactive, swimming sluggishly or dwelling at the shallow part of the pond during the daytime, an infection may have occurred. The first remedial step is to drain water to a depth of 50 cm and refilling the pond with a large volume of new water. This flushing should be done as frequent as possible to allow shrimp to molt. This practice has the following benefits: it removes material that had caused the problem and induces molting which helps remove the pathogen that may have adhered to the shell of shrimp. However, heavy flushing method is not practical in some countries like Taiwan because it can induce shrimp shock and stress. Taiwanese practice does not allow daily high rate of water exchange (2–5 %), hence shrimp are not used to a sudden change of water condition such as in a heavy flushing. But high rate of daily water change is a common practice in Thailand, therefore it causes little or no stress to shrimp. If this remedial action fails to stem the infection, chemical treatments are recommended for the following:

1. Black gill disease. This disease occurs when the pond bottom is excessively filthy which accelerates the proliferation of the fungi, called Fusarium. Treatment is normally ineffective: malachite green at the rate of 1.5 1/ha can be used at a water level of 50 cm for one day. This chemical however is expensive and can be harmful to users. Therefore the best solution is to harvest the shrimp and transfer the selected uninfected shrimp to the other pond.

2. Red gill disease. Generally protozoa of genus Zoothamnium or Epistylis are found in natural seawater. They will spread very fast if the pond condition becomes polluted. These protozoa attach to the gill causing gill inflammation and depriving the shrimp of oxygen. Treatment includes reducing the water level to 50 cm and applying formalin at the rate of 120 1/ha all over the pond area. This should be done in the morning when the pond water is cool and level of dissolved oxygen is increasing. Aerators are operated to full capacity. The period of treatment is four hours before heavy flushing.

3. Tail rot disease. It is caused by Chitinoverous bacteria and fungi. Treatment is the same as for the red gill disease. If fungus is the pathogen, malachite green can be applied as in the case of black gill disease.

4. Ectozoic algae symptom. When pond bottom becomes filthy, some blue green algae will attach to the shrimp shell during burying or feeding. Hence molting frequency and growth are retarded. Remedial action is by reducing water level to 50 cm and employing copper sulfate (CuSO₄) at the rate of 1.5–2.5 1/ha. Allow one day while aeration is carried out thoroughly and water is later heavily changed.

5. Red colouration disease. It leads to reduction in shrimp activities and no feed acceptance. Main cause is contamination of feed by fungus as a result of long storage. The fungus is ingested by shrimp causing the disorder in digestion. As with the black gill disease, this is difficult to cure. Furazolidone may be administered at the rate of 50 1/ha with the water level at 50 cm. Allow one day before beginning heavy flushing.

6. Soft shell disease. Infection from Vibrio bacteria originaling from polluted bottom is one of the causes of soft shelling. The other factor is deficiency in natural food like plankton. It can be remedied by using quaternary ammonium compounds at the rate of 5–6.5 1/ha for one day followed by repeated water exchange 3–4 times to induce new molting. Polluted bottom material should be removed while the pond should be subsequently fertilized to enhance plankton growth.

7 Records of Feed Management

1. Feed storage inventory. To ensure that there is no expired feed left in the store, the oldest stock must be firstly used (first in - first out). Sometimes it is difficult to remember which sacks are the oldest batch because some factories do not label the production dates. A good inventory system helps solve the problem. For each delivery, the new sacks of feed should be stacked on the wooden platforms in the same row. Labelling the date of delivery at each platform should be done and recorded. Labelling of each sack, if feasible, is much recommended. A sample of inventory record is as follows:

   Feed Storage Inventory

   	Month                    Year
   Type of feed
   Feed A : Brand name	Size	Price	Baht/kg
   Feed B : Brand name	Size	Price	Baht/kg
   Feed C : Brand name	Size	Price	Baht/kg
   Feed D : Brand name	Size	Price	Baht/kg

   Inventory

   Incoming				Outgoing
   Date of delivery	Platform no.	Type of feed	Amount (kg)	Date of use	Platform no. feed	Type of (kg)	Amount	Pond

   
   

   Type A	Total delivery	kg	Total use          kg
   	Balance	kg	(transfer to next month)
   Type B	Total delivery	kg	Total use          kg
   	Balance	kg	(transfer to nextmonth)
   Type C	Total delivery	kg	Total use          kg
   	Balance	kg	(transfer to next month)
   Type D	Total delivery	kg	Total use          kg
   	Balance	kg	(transfer to next month)

2. Feeding records. Feeding records are very useful to determine the efficiency of your feeding programme and costs of feed for each pond. The past records can be used as guideline for monitoring feed consumption in each pond.

   Feeding Record

   Pond               

   quantity in kg
   Date	1st meal		2nd meal		3rd meal		4th meal		Total feed
   	Pellet	Fresh	Pel.	Fre.	Pel.	Fre.	Pel.	Fre.	Pel.	Fre.

   Total pellet                       kg
   Total fresh feed by wet weight                       kg, by dry wt                kg
   Total feed                       kg by dry weight.
   Total shrimp harvested                       kg
   FCR                                                    

3. Pond management record. The parameters in this record are used for adjusting the feeding programme.

   Pond Management Record

   Pond               

   Number of seed stocking                                    pcs, pond size                                     m²
   Stocking density                                    pcs/m², Date of stocking                                    

   Date	Depth	Sal.	Temp.	pH	DO.	Water Change	Fertilizer	Chemical	Wt.	Length
   	cm	ppt	°c		ppm	%	type/kg	type/kg	gm	cm
   Total
   Ave.

   Total shrimp harvested                                kg,   Number harvested                        pcs
   Average size of shrimp                                gm,   Survival rate                                  %
   Size range from                  gm to                  gm,   Income                                      Baht
   Other by-products harvested                        kg,
   Total animals harvested                                kg,
   Total income                                                Baht,

   If there are any special events observed such as:

   • mortality
   • diseases
   • animal refuse to feed
   • obvious wastage
   • pump failure
   • aerator failure
   • over feeding
   • etc.

these should be remarked in the record. If it is possible, the colour of pond water and turbidity should also be recorded.

VII. DEVELOPMENT OF ECONOMIZED MARINE SHRIMP FEED

The ingredient composition of recommended marine shrimp feed formula is as follows:

* = The range of percentage following the sizes of feed

VIII. DEVELOPMENT OF ECONOMIZED MARINE FINFISH FEED

1. Lates seabass feed formula (moist pellet)

2. Grouper feed formula (moist pellet)

IX. OTHER DUTIES

As requested by the project manager, the project performance Evaluation Report and Project Progress Report for TPR meeting have been prepared. Since it is the first TPR meeting of the project, considerable assistance in organization of the meeting have been given. With the change in project execution from Thai Government to FAO, the FAO formalities were introduced including purchase orders, reporting system, personnel management, etc. During field visits, not only the knowledge of feed management, but also shrimp pond management, pond design and construction, and the new technology to solve shrimp price crisis, were transferred to farmers and government officials. One lecture on Shrimp Pond Management was presented during the Conference on How to Improve the Shrimp Price Crisis Situation, organized by Kasetsart University, Chulalongkorn University and DOF at NIFI, Bangkok on 26 January 1990.

X. RECOMMENDATIONS

1. Due to the heavy field work in research programmes on shrimp feed management, additional staff and technicians should be urgently recruited to follow up the experiments in various remote areas.

2. The second feed Technology Consultant should be recruited as soon as possible to assist in testing of feed milling equipment and feed manufacturing so that the project shrimp feed formulae can be produced on time to be used in long term experiments.

3. The selected site for trial experiment on shrimp feed formulae at Namchai Shrimp Farm, Samutsongkhram should be given up because that site is no longer suitable for shrimp culture. The ponds and water system in the Samutsongkhram area, the first site where intensive P. Monodon culture was established, were poorly designed. With the shallow sand bars blocking the pond water outlet and industrial waste discharging into the open sea, the pond bottoms and water supplies have deteriorated.

4. In trial experiments on shrimp feed formulae, it is impossible for the project to provide the feed produced by the project machines free of charge to the farmers. Therefore it is necessary to sell the feed at production cost in order to encourage the farmers to test project feed. For the sites where feed manufacturing machines have been designed by the project, some minor imported ingredients like vitamins, binders, minerals, etc., should be supplied by the project.