Most of the author's work is dealt with in detail in a series of appendixes to this report. This section is intended only as a summary of that work, together with additional observations.
The author considers the current vitmix (poultry vitamin concentrate) inadequate, both for finfish and prawns. The vitamin levels contributed to diets through the addition of 2.5%1 of the vitmix (1/100 dilution of Roche vitamin concentrate 428/3) to a moist diet is listed in Appendix 2 and compared to the recommended dietary levels for marine prawns and marine finfish. Levels of all vitamins except A, D3 and B12 are deficient. For the experimental feeds made during this consultancy (see sections 4.3 and 4.5) a modified version of this premix (the vitamin C level was increased fourfold through the addition of feed grade vitamin C) was employed, in the absence of anything better. However, this was regarded as a temporary measure; the vitmix must be improved in the future. It is not possible to increase the levels of the deficient vitamins by reducing the dilution rate of the concentrate since the very high levels of vitamins A and D3 in the latter would cause an excess in the diet and possible hypervitaminosis.
While the feed trials were in progress, an alternative vitmix designed for finfish was located by LKIM staff in Kuala Lumpur. The potential result of adding it as its recommended inclusion rate of 0.2% in a dry diet is also shown in Appendix 2. The substitution of this vitmix would be a great improvement on the existing premix and it is suggested that it be used in the immediate future until a more satisfactory premix can be made (see below). It is still deficient in some vitamins, specifically vitamins E, niacin, biotin and choline. Inositol is absent and the vitamin C level is much too low. On a dry matter basis (for comparative purposes), use of the Agrimate vitmix and the current diluted Roche 428/3 poultry mix would cost approximately M$ 56 and M$ 54/t of feed respectively. If substituted in feeds the Agrimate premix should be used at the following inclusion rates: moist feeds (with about 45% moisture) -0.1%; dry feeds (with about 10% moisture) - 0.2%; and trash fish - 0.04%. Please note that the formulations given in this report are all for feeds extended in moist form, even though some are subsequently to be dried. The 0.2% inclusion rate given above for dry feeds would only apply if all the ingredients were dry and the feed was to be made by the normal pellet mill process used by commercial feed manufacturers. (Further notes about inclusion rates are given in each appendix containing formulations.)
As stated above, the Agrimate premix is, though a great improvement, still not satisfactory. It is therefore recommended that Roche Agrimate, Sin Heng Chan, or Union Farm be asked to make up an “Improved Vitamin Concentrate” for the project. The formulation for this concentrate is given in Appendix 3. When available, it should be diluted 1:6 with wheat pollards and used at the following rates: moist feeds - 2.5%; dry feeds -4.0%; trash fish - 1.0%. (Please refer to the note in the previous paragraph). It is estimated that, on a dry matter basis, use of the improved vitmix at the recommended inclusion rates would cost about M$ 80/t of feed.
1 0.8% was being used in the micro-encapsulated post-larval prawn feed (see Appendix 8)
It should be noted that the potency of vitamins, vitamin concentrates and vitmixes declines during storage particularly when feed is exposed to light and high temperatures. Pure vitamins and vitamin concentrates should be kept refrigerated or in an air-conditioned room for not longer than six months. Since these are expensive materials they should not be bought in quantities greater than those expected to be used within 6 months.
Work elsewhere (e.g., Thailand), has shown that seabass and grouper fed trash fish, grow and survive better when a vitamin supplement is added. Trash fish may cause deficiencies in thiamin especially. It is suggested that when the improved vitmix is available and its cost is known, an experiment to test the cost effectiveness of adding it at 1% (1 kg diluted improved vitamin concentrate to 99 kg trash fish) to trash fish be carried out. Meanwhile a preliminary trial adding 0.04% (40 g vitmix in 100 kg of trash fish) of the Agrimate fish vitmix could be conducted with seabass.
The results of a survey of the feed ingredients available in the Penang/Kedah area are given in Appendix 4. Suppliers' addresses are provided in Appendix 6. Raw materials available elsewhere are noted in Appendix 5.
It should be noted that raw material costs appear to be higher in Johor than in Penang/Kedah. The effect of this on the raw material costs of the feeds formulated in this report, which were based on the cost of feeds purchasable by LKIM, Sg. Merbok, can be calculated by substituting local prices. No local source of feed ingredients, except fresh materials such as trash fish, was located in Terengganu/Besut. There are no feed mills in this area.
In the feed formulations given in this report, the fishmeal incorporated has been Thai fishmeal, because this is the most readily available. It should be noted that many Thai and Malaysian fishmeals are of poor quality due to poor processing and poor quality fish intake. Good quality shrimp feeds should contain high quality fishmeals (e.g., from Chile) and it is suggested that these be substituted in the formulations for shrimp if LKIM decides to make its own feeds on a routine basis. High quality fishmeals are more expensive on a unit cost basis but could be added at a lower inclusion rate.
LKIM staff have been shown how to substitute one ingredient (e.g., Peruvian fishmeal for Thai fishmeal) for another in a formulation, together with the adjustments to the inclusion rates of other ingredients which are necessary to balance the diet. The formulations given in this report were balanced for oil, protein, protein/energy level, minerals and amino acids. However, minor adjustments like that just mentioned may be made simply by balancing oil and protein levels. Basic information on some local feed ingredients and an example of balancing a diet through ingredient substitution is given in Appendix 19.
Blood meal (if of good quality), fresh blood, and fish silage are of potential future use in seabass/grouper feeds if sources can be identified. Blood meal is used in Japanese yellowtail feeds and fish silage has effectively been used in salmonid feeds. LKIM should suggest that MARDI and the DOF research into the production and use of these products in marine fish feeds.
Until recently, branded post-larval prawn feeds had been used at Sg. Merbok for rearing early post-larvae (P10-P25). However, these proved expensive (Gold Coin M$ 3.2/kg; “President Feed Brand” M$ 4.2/kg) or unsatisfactory (Ang Hock). Recently, therefore, a micro-encapsulated feed has been used for seabass larvae, either alone or as a supplement to the dry branded feeds. The formulation of this micro-encapsulated feed (based on whole egg) includes vegetable oil and is regarded as an unsuitable lipid; action had already been taken to replace this with cod liver oil1 with visibly beneficial results on pigmentation and vigour.
However, the encapsulated diet, though very easy to prepare on a small scale, would be cumbersome to produce and store when the hatchery had up to 3 million early post-larvae at any one time. It is also extremely expensive (raw material cost = M$ 47.6/kg on a dry matter basis). The author therefore formulated an alternative post-larval feed based on upgraded moist formulations for grow-out prawns. This was tested on early post-larvae over a 17-day period (P8-P24) and compared with the micro-encapsulated feed. The experimental feed was fed in three forms: moist; as a dry coarse crumble (1–4 × 2 mm); and as a dry fine crumble (0.25–1 mm). The formulation, calculated analyses, and method of production of these feeds are given in Appendix 8. On a dry matter basis, the raw material cost of the trial feed was M$ 1.8/kg. The feeding trial with this feed began on 21 November and ended on 7 December. Details of the experimental procedure, together with the results and conclusions drawn are given in Appendix 9.
The cost effectiveness and superiority of the new post-larval feed have been amply demonstrated. Its use, whether in moist or dry form, would result in 1.2–1.8 times greater hatchery production of post-larvae than the existing feed. Larger and more active animals for stocking in ponds would become available. Survival rate up to 67% were achieved in the trial compared with about 25% in previous large-scale batch rearing at Sg. Merbok. Additionally, feed manufacturing and storage problems would be lessened and the cost of feeding post-larvae would be reduced to about 13% of that of the micro-encapsulated feed. The raw material unit cost (dry basis) of the new diet is also M$ 1.4/kg cheaper than the Gold Coin post-larval feed and M$ 2.4/kg cheaper than the President Brand Feed postlarval diet.
It is suggested that the new diet be used in future, preferably in the “dry ground” (fine crumbles, 0.25–1 mm in size) form. The use of the micro-encapsulated egg diet, alone or in combination with commercial post-larval feeds, should be discontinued. When available, the improved vitamin mix (Appendix 3) should be substituted for that used in the experiment; it is anticipated that this will result in further improvements in performance. Until the improved vitmix is purchased, the use of the Agrimate fish vitmix is suggested. It should be noted, however, that this vitmix does still not respond to the specifications suitable for shrimp or seabass feeds and its use should only be a temporary measure. Its use would be a great improvement on the existing vitmix. The inclusion rate of all vitmixes mentioned is indicated in Appendix 8, note 4.
The financial benefit of using the new post-larval feed can be illustrated as follows:
If the new diet were used, instead of the egg diet, in a hatchery designed to produce 10 million post-larvae/year (such as is targeted for the Sg. Merbok hatchery) the effect would be substantial. If the targeted production had been based on an assumption of 60% survival from P5 to sale (as was exceeded by the new diet in this trial), a survival of 37% (as achieved by the control egg diet) would result in a loss of 3.83 million post-larvae, at a sales value of M$ 153 2001. The total financial benefit of using the new diet would therefore be M$ 153 200, plus the savings in feed costs (M$ 12 406), i.e., more than M$ 165 000 annually.
A grow-out diet for P. mondon was formulated by the previous consultant (Chow, 1984, Table 6). Although this was tested after he left and considered successful, it is not currently in use for pond culture at Sg. Merbok. This appears to be mainly due to a concentration of staff on hatchery and pond-rearing operations which does not leave enough time for feed manufacture on site. Also two, commercial feeds are locally available (see Appendix 7). However, the Gold Coin feed is regarded as expensive (list price for growers is M$ 2.3 /kg) and the Ang Hock feed has extremely poor and deteriorating water stability. Ang Hock had changed hands within the past year; quality has since deteriorated. On a visit to their factory it was found that the fish oil being used had been in stock for more than one year. The staff of Ang Hock are anxious to improve the quality of their feed and requested help in this matter. In a subsequent meeting, the author provided general guidance to their part-time feeds consultant.
The author visited 5 feedmills in the Butterworth area (Appendix 6) but only the two noted above currently produce shrimp feeds. Subsequently, he was told that another firm was selling shrimp feeds but this was not visited. Other shrimp feeds are potentially available however; some are noted in Appendix 7. In a comparative trial the author conducted in Guam in 1982 (using P. monodon and P. merguiensis) the feed made by President Enterprises 2 of Taiwan gave the best results when compared to the limited Taiwanese and North American feeds then on the market. Attention is drawn to the fact that there are two shrimp feeds made in Taiwan known as President Feed. That made by President Enterprises 2 is the original brand, which is also made under licence by San Miguel in the Philippines 2. The author was involved in the initial development of the Gold Coin 2 feed but is not responsible for its current formulation. He is listed as an honorary consultant to Hanaqua2 in their literature (in common with Shao-wen Ling and I-Chiu Liao) but was not involved in the formulation of their feeds and did not have the opportunity of comparing the performance of prawns fed the many brands of feed (more than 30 in Taiwan alone now) currently available. Though such trials are conducted by commercial feed comapnies, the results are not released. In Johor, more information was obtained about the two other local brands of shrimp feed. Aquafeed and Chee Kheng (see Appendix 7). BARC, Gelong Patah reported that the Chee Kheng feed gave better results than Gold Coin. Aquafeeds diet had not been tested. The President Enterprises feed was believed by BARC to be better than that of any other type, including that made at the centre. Aquafeeds only make starter feeds to customers' request. They market separate grower feeds for Macrobrachium. banana and tiger prawns. Their feeds are stated to be enriched with vitamins and other additives including preservative, antioxidant and vitamins. It is noted that their feed contains supplementary inositol, which is absent in the Agrimate vitamin premix (see Appendixes 2 and 3). The Gold Coin shrimp feed is reported to contain a small quantity of the binder Basfin. This is believed by many farmers to cause unpalatability and stunting. This is very unlikely at the inclusion rates used (although problems have been encountered by an Indonesian feed manufacturer who used the product at levels far in excess of the manufacturer's recommendations). However, farmers' beliefs, whether founded on fact or fiction, are difficult to refute, so the author suggested to Gold Coin that it could be in their marketing interest to find a substitute for Basfin. Aquafeeds are trying to develop a tiger shrimp feed with lower specifications and cost.
Work on shrimp feeds is proceeding at the BARC, Gelong Patah. Their dietary raw material cost was said to be M$ 1.00/kg. Experimental feeds have been produced by most extrusion, followed by sun-drying. Water stability was poor (in the author's view because the moisture content -60–70% - at extrusion was much too high) and sun-drying is thought to cause vitamin damage via UV light (though BARC are not now incorporating supplementary vitamins). BARC has therefore now purchased a CPM Model CL-3 laboratory pelleter and kerosene fired blower heater. The estimated output of the pelleter is 50 kg/h and it is recognized that pellets produced by it will have poor water stability unless expensive binders are incorporated in the formulation.
Future plans for Sg. Merbok include smallholder prawn farming. Initially twenty-five 1 ha units are planned, with further development anticipated. The establishment of other, 50–100 ha, farm complexes was envisaged in discussions with ADB. In the view of the high cost of commercial prawn feeds, LKIM wish to consider the possibility of each farm unit producing its own feed (see section 4.8). In response to a request to formulate a feed for grow-out prawns the author has formulated two diets. Details of these formulations are given in Appendix 10. The current raw material cost of these feeds (on a dry matter basis) would be M$ 0.9/kg and M$ 0.74/kg respectively. This compares favourably with the cost of commercial brands, whose list prices (Appendix 7) range from M$ 1.4 to 3.1/kg. Allowing for an estimated 10% moisture in these latter feeds, their dry matter cost becomes M$ 1.56–3.44/kg. Recommendations for a trial of the formulations given in Appendix 10 are given in section 5.
During the visit of the previous FAO feeds consultant, three semimoist test diets for seabass juveniles were made and a feeding trial was initiated. Though completed subsequently, no review of the results of this trial was made. That experiment has therefore been discussed in detail in Appendix 11. While a cursory glance at the bare results indicated that fish fed trash fish grew better than those fed the test diets designed by Dr Chow, careful examination of the results reveals a number of other interpretations. Survival of fish fed trash fish was very low and one replicate was apparently lost (subsequently it was discovered that fish from this replicate were used to replace mortalities in other treatments. This practice destroys the purpose of the experiment. Replicates must not be removed; nor should mortalities be replaced). All fish appear to have been grossly overfed in this trial. The most interesting result, which was missed because the trial was not accurately analysed, was that the artificial diet with the highest protein content gave the best overall animal performance of the three feeds tested. In view of the conduct of the experiment this deduction must be regarded as tentative; however, it corroborates the experience of other workers in this field. This result, and the experience of others, helped in designing the test diet for the 1985 experiment, which had a much higher protein level (45% compared with 34–36%).
Unfortunately, no seabass of the size used in the 1984 experiment (36–38g) were available for use during the consultancy, so 1 inch and 3 inch fingerlings were used. Details of the semi-moist feed formulated for this trial are given in Appendix 12. While the “Chow” diets (Appendix 11) were based on all-dry ingredients, moistened to produce a semi-moist feed, the new formulation includes 50% of fresh ingredients (trash fish and squid). Details of the experiment to test the new formulation are given in Appendix 13.
The test diet, which had a protein level of about 45% (compared to the 34–36% levels tested in 1984) was accepted immediately by the fish, without weaning. Growth rate (weight increases of 3.2–4 fold within 20 days), survival rate (76.5–85.0%), and feed conversion efficiency (1.86: 1 to 1.13:1) were good. The use of the moist feed SB No. 1 was also cheaper than using filleted trash fish, on the basis of unit weight of fish produced. However, the overall performance of diet SB No. 1 was not so good as filleted trash fish. There are indications that the larger fish perform better on the test diet than the younger ones.
Based on the results of this experiment (which is discussed in Appendix 13) it is conjectured that the SB No. 1 formulation would be acceptable as a grow-out feed but needs improvement for use with fingerlings. Two improved formulations (diets SB No. 2 and SB No. 3) are given in Appendix 14; these need to be tested against filleted trash fish as a control in future trials.
This experiment has demonstrated a major step towards designing a cost effective alternative to trash fish for fingerling seabass feeds and may also have identified an adequate grow-out diet. Further work on this topic is suggested in section 5.
During a visit to BARC, Gelong Patah, it was stated that they have experimented with a semi-moist seabass feed incorporating 50% trash fish. Unlike the result of the trial at Sg. Merbok, they found that it was difficult to accustom the fish to accept the semi-moist feed and that at least a week of weaning off trash fish was essential. In the Sg. Merbok trial no weaning was necessary and the fish accepted the experimental diet immediately after being taken off trash fish. This may have been because 1% squid was included in the ration as an attractant.
The Primary Production Department (PPD) at Changi Point, Singapore, have been working on the development of artificial seabass and grouper feeds for more than six years. An attempt was made to discuss their progress but although an appointment was made, it was not kept by PPD staff.
Shrimp maturation work is not currently being carried out at Sg. Merbok. Similarly, though there is a broodstock population maintained in cages, it was not the spawning season for seabass during the consultancy.
The previous FAO feeds consultant added a liquid vitamin supplement to trash fish fed to 6 seabass broodstock held in the hatchery in 1984. The effect of this dietary enrichment was reported (Chow, 1984) to be spawning behaviour by all fish within 7 days of first presentation of the modified feed. Coagulated milt was also observed on the water surface. Unfortunately all fish died in subsequent water quality problems in the hatchery so this work was not continued. Broodfish are now maintained in cages on unsupplemented trash fish.
Although a broodstock diet for P. monodon was formulated by the previous consultant, the author does not recommend this as satisfactory for use as a shrimp maturation diet.
New formulations for experimental marine finfish broodstock diets and shrimp maturation feeds have been designed. Details are given in Appendix 15.
The culture of tilapia in marine cages is being contemplated by LKIM because of the greater availability and cheapness of seed stock.
Although not in the author's terms of reference, LKIM requested information on tilapia feeds. An excellent review of tilapia feeds and feeding exists (Jauncey and Ross, 1982) and it is suggested that LKIM purchase this book for reference purposes.
The specifications for tilapia feeds are not so demanding as those for marine finfish. Tilapia feeds should therefore be cheaper. Additionally tilapia are known to thrive on dry pelleted feeds (though there are some reports from the Philippines of better results through the use of moist feeds).
Suggested formulations for feeds for tilapia grown in cages are given in Appendix 16. Raw material costs are M$ 0.67/kg for the fingerling diet and M$ 0.59/kg for the grow-out feed (both on a dry matter basis).
Gold Coin market a tilapia grow-out feed (3.5% oil; 27% protein) at M$ 0.70/kg (M$ 0.78 on dry matter basis). Many Taiwanese and Japanese feed companies also market tilapia feeds.
The annual production of a 25-ha model shrimp farm consisting of 1-ha small holding operators would be about 75 t/year at projected production levels. The feed requirement, based on an as-fed FCR of 2.2:1 (2:1 on a dry matter basis) would be about 165 t/year if dry pellets were used. This represents a daily average feed requirement of about 0.45 t only. Even a 100-ha farm would only use an average of 1.8 t/day of dry feed. Laboratorysize pelleters are not designed for continuous operation. The smallest basic commercial pelleters, which are capable of producing 4–8 t in an 8-hour shift, would be idle most of the time and would require ancillary equipment, such as a steam boiler. Additionally these small basic units would not have the special modifications necessary to produce a water-stable pellet.
In examining equipment requirements for such farm units, effort has been concentrated on the production of shrimp feed by moist extrusion, followed by sun- or forced air drying. This process has been used for making the shrimp diet develop during the consultancy. The feed produced by the equipment suggested could also be used in a semi-moist form, without drying, if made on a daily basis. All formulations given in this report (for seabass as well as for shrimp) have been based on moist extrusion production techniques. The process is simple and can readily be learnt by previously unskilled personnel. The equipment is cheap and easy to install. It can be bought in sizes appropriate to the farm size and added to later if farm size or output increases. A 25-ha farm would need to extrude an average of less than 1 t/day, whether the feed is used in this moist form or in dried form. The maximum daily requirement for moist extrusion (due to variations in total farm biomass caused by seasonality or market requirements) is unlikely to exceed 6 t/day (equivalent to about 3 t/day of dry feed).
Appendix 17 lists the major equipment necessary to produce up to 6 t/day of moist feed or 3 t/ day of dry feed. The name and address of the company where this equipment can be purchased are given in Appendix 6.
In addition to the equipment listed in Appendix 17, the following uncosted facilities would be required:
A most feed preparation building (approximate area = 100 m2) with floor drains, water and power supplies, and a sink unit.
A ventilated dry feed store capable of holding up to 40 t (approximately 50–100 m2).
A cold store capable of holding up to 5 t.
The total cost of equipment (excluding buildings and services) for feed production for a 25 ha shrimp production unit harvesting 75 t of shrimp per year would range from M$ 50 000 to M$ 111 000 for moist feed production. Equipment suitable for converting moist feed into dry pellets would cost a further M$ 7 500–50 000, depending on the sophistication of the system employed. The total equipment cost for producing up to 3 t/day of dry feed by the techniques described would therefore range from M$ 58 000 to M$ 161 000. Assuming depreciation over 5 years and actual annual feed production of 150 t (on a dry matter basis) this represents an equipment cost of about M$ 0.08–0.21 per 1 kg of feed. However, the plant would be capable of producing up to about 1 000 t/year if used continuously so sharing one feed production unit between two and four 25-ha farm units would be possible, providing the times of peak feed requirement of the various farms did not coincide. This would reduce the equipment cost of a dry feed to M$ 0.01–0.03/kg.
It should be noted that a complete dry pelleting plant (Buhler) capable of producing 5 t/day of water stable shrimp feed would cost more than M$ 500 000, plus erection costs and the building to house it. If the primary business activity is to be feed production, installing this type of machinery in a labour-saving and efficient design would be much the best option. However, where feed production is only to be ancillary to the main activity of producing marketable shrimp, the simple, labour-intensive system described above is recommended.
During the consultancy, methods for feed production were demonstrated; and on-the-job training was provided for counterpart staff through tutorials, in ingredient selection, formulation, feed manufacture, and general nutritional matters.
The feed-related aspects of a recent LKIM/FAO report (Tan et al., 1985) on commercial finfish cage culture were also reviewed, at the request of LKIM. This informative report contains the following points of dietary interest (together with some comments, where appropriate):
All six cage culture operations in the case study used “trash fish”, including clupeids or sardines (Clupea spp.), mackerel (Caranx spp.), anchovies (Engraulis spp.), mullet (Mugil spp.), catfish (Tachysurus spp.), jewfish (Pseudosciaena spp.), lizard fish (Saurida spp.), squids and mantis shrimp. Sardines were preferred because of their lower bone content. (Author's note: Most operators use chopped whole trash fish but some fillet the fish first. Coarse chopped whole fish results in much cage fouling, wastage, and damage by predators to nets. It has been found in Japan that the feeding of excess amounts of trash fish to another member of the marine Percoidae, the yellowtail, causes a decrease in water transparency due to fat floating on the surface, eutrophication, and incidences of red tide and disease.)
Trash fish prices ranged from M$ 0.32 to 0.33/kg in Bukit Mertajam and from M$ 0.17 to 0.25/kg on the Penang east coast (April 1985). The current convenience of obtaining trash fish and its apparent cheapness precluded operators from thinking of alternative feeds. (Author's note: It should be remembered that trash fish may not always be so abundant or as cheap, particularly as cage farming expands. This has already become a problem in Thailand. Trash fish is not necessarily a cheap feed. Converted to a dry matter basis the prices quoted in the report become M$ 0.81–1.57/kg if whole chopped fish is used. If the fish is filleted the dry matter unit feed cost could be as high as M$ 2.85/kg.)
Bukit Tambun farmers faced trash fish supply problems for 2–5 days per month while those on the Penang east coast were without trash fish for 3–4 days per month (the maximum reported was 10 days). Excess trash fish was preserved in ice; one culturist had a freezer.
(Author's note: The use of a moist diet would lessen the need to store trash fish for periods of shortage since it contains only 50% wet ingredients. The dry ingredients can be stored either individually or in mixed form at ambient temperatures with the addition of trash fish. If, in the future, a successful and economical dry diet can be developed for seabass and grouper, this would revolutionize storage and feeding operations. The preparation of trash fish on a daily basis is extremely time-consuming if done well.)
Culturists fed their fish three times per day for fish up to 5 inches (12.7 cm) in size. Larger fish were fed less frequently, sometimes only once every two days. This practice conforms with the results of the early research work done by Teng and his colleagues in Penang.)
Feeding rates were given in the report but, since no length/ weight relationship is quoted, it is not possible to deduce the percentage biomass fed per day. Feed presented daily ranged from extremes of 3.3 g/fish for 5–13 cm (2–5 inch) fingerlings to 22.5 g/fish for 25–35 cm (10–14 inch) fish.
Feed conversion ratios (determined by dividing total farm weight of trash fish consumed by total farm weight gain) ranged from 4.9:1 to 10.1:1 (average 6.7:1). This represents an AFCR1 of 1.4:1 on a dry matter basis, which is acceptable for fish).
None of the culturists used growth promoting hormone. (Author's note : Both 17-α methyltestosterone and nitrovin have been found to have a growth promoting action in feeds for groupers.)
On average, overall feed costs for all four species were 21.7% of total operating costs (including fingerling costs and depreciation), while fingerling costs were very high (51.7%). Actual feed costs were similar for grouper and seabass but assumed lesser significance as a proportion of total costs in the case of grouper because of the inflated total costs due to fingerling purchase price.
A sensitivity analysis showed that, even though the cost of trash fish was low, cost changes of ± 10% could exert +23% or -22% changes in profit. A similar effect was exerted by 10% changes in feed conversion ratio.
