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Growth and survival of Penaeus monodon juveniles fed a diet lacking vitamin supplements in a modified extensive culture system
Aquaculture, 101 (1992) 25-32 Elsevier Science Publishers B.V., Amsterdam
25
Growth and survival of Penaeus monodon juveniles fed a diet lacking vitamin supplements in a modified extensive culture system Avelino T. Triiio, Veronica D. Pefiaflorida and Edna C. Bolivar AquacultureDepartment,SoutheastAsian FisheriesDevelopmentCenter, P.O. Box 256, Iloilo, Philippines (Accepted I6 April 199I )
ABSTRACT Trifio, A.T., Peiiaflorida, V.D. and Bolivar, E.C., 1992. Growth and survival of Penaeus monodon juveniles fed a diet lacking vitamin supplements in a modified extensive culture system. Aq:z.wulture, 101: 25-32. Penaeusmonodon juveniles with mean initial weight from 0.1 I to 0. I7 g were fed diets with and without vitamin supplement. The diets contained 34Ohprotein and 8% fat. The animals were stocked at 5/m* in 320-m* earthen ponds and reared for 135 days. Growth, survival, net production, and net cost of production per kg of P. monodon were not significantly affected even if supplemental vitamins were eliminated from the diet. The absence of extra vitamins from the diet may have been compensated either by the basal diet used or by ingestion of natural food existing in the ponds. In either case, the possible influence of vitamins from these sources is manifested in the overall effects on growth, survival and net production of prawns when no vitamin supplement is added to the diet. Results obtained showed that the difference between diets in cost of production was statistically not significant (P> 0105). However, the favorable cost difference of P 18.02 per kg of prawns produced would make it more profitable to use the diet without vitamin supplement in a modified extensive culture system.
INTRODUCTION
The slump in the export market of P. monodon has caused some fish-farm operators to shift from an intensive to a modified extensive system (MODEX ) of culturing prawns. Comparative economic analysis of the different prawn culture systems (Posadas, 1988 ) indicates that under existing market conditions, MODEX becomes economically profitable only if the cost of production is lowered. One way of reducing cost is through feed inputs since those contribute 55% to production costs (Posadas, 1988 ). Elimination of the extra vitamins from the diet will give substantial savings in feed cost of approximately P lO.OO/kg (Pascual and Catacutan, 1990) 0044-8486/92/$05.00
0 1992 Elsevier Scierce Publishers B.V. All rights reserved.
A.T. TRIRO ET AL.
26 TABLE 1 Composition and cost per kg of the diets Ingredients (%)
Diet 1
cost (P)
Diet 2
cost (P)
Tuna-fish meal Prawn-head meal Soybean meal, defatted Rice bran Wheat gluten Bread flour Cod-liver oil Soybean oil Lecithin Mineral mix’ Vitamin mix’ Propionic acid BHT
16 15 35 12 3 10.7 1.5 2 1.5 1.5 0.1 0.2
2.56 1.50 1.28 0.42 2.27 1.07 1.20 0.75 2.20 10.50 10.50 0.11 0.16
16 15 35 12 3 12.2 1.5 1.5 2 1.5 0.0 0.1 0.2
2.56 1.50 1.28 0.42 2.27 1.22 1.20 0.75 2.20 10.50 0.00 0.11 0.16
Subtotal Processing and bagging Total
100.00
34.52 --10.53 45.02
100.00
24.17 10.50 34.67
‘For compositio n of mineral and vitamin mixes see Deshimaru and Kuroki ( 1974).
compared to the same diet with vitamin supplement (Table 1). Although vitamins are essential food constituents in the diet, they may also be provided by plant and animal food organisms endemic in ponds. Under MODEX these food organisms are grown during pond preparation and maintained for the whole culture period to serve as natural food base for the prawns. This study was undertaken to determine the growth and survival of P. monodon when fed a diet without vitamin supplement under a modified extensive culture system. MATERIALS AND METHODS
Design of experiment The study was conducted for 135 days in nine 32-m* ponds at the Leganes Brackishwater Station, Iloilo, The Philippines. Three replicates were assigned in a randomized complete block design (RCBD) using the following treatments: supplemental diet I (with vitamin supplement ); supplemental diet 2 (without vitamin supplement ); control (without supplemental feeding). Prawn fry ( PL20) with mean initial weight from 0.11 to 0.17 g were obtained from the prawn hatchery at SEAFDEC AQD Tigbauan Research Station. The fry were brought in aerated plastic bags when the ponds were ready for stocking. Animals were weighed before stocking and subsequently weighed every 15 days.
EXTENSlVEP.MONODONCULTUREWITHOUTSUPPLEMENTALVITAMINS
27
Pond preparation
The ponds were prepared to induce growth of plankton to serve as natural food base for the prawns. Pond preparation consisted of letting the pond bottom dry for 1 week, applying hydrated lime at 32 kg/pond and filling the pond with water to a depth of 30 cm. Fertilization was done with chicken manure and inorganic fertilizers. Chicken manure was applied at 32 kg/pond, equally divided in two plastic sacks and suspended at opposite sides of the pond. A 1: 1 ratio of inorganic fertilizers (45-O-Oand 18-26-o) were broadcasted at 1.28 kg/pond. Upon development of luxuriant growth of plankton (pond water turned light brown in 5 days) the pond-water level was raised to 60 cm. Stocking was then carried out after 3 days. Diets
Two supplemental diets were formulated (Table 1) to contain around 34% protein and 8% fat (Table 2). Diet 1 had extra vitamins while diet 2 had none. The other ingredients were the same in both diets except for bread flour ( 10.7% for diet 1 and 12.2% for diet 2). The amount of bread flour was altered to compensate for the eliminated vitamins. The difference in calculated M.E. between the two diets was only 15 kcal/ 100 g (Table 2). The diets were prepared following the procedures of Pascual ( 1983 ) . The proximate analysis of the diets was performed at SEAFDEC AQD Centralized Analytical Laboratory using standard methods ( AOAC, 1984). Culture management
The prawns were stocked at five individuals/m’ after acclimation to pondwater temperature and salinity. Water depth was maintained at 60 cm for the first month and gradually increased to I m thereafter. Every spring tide about 30% of the pond water was replenished once a day for 3 consecutive days. Plankton growth was maintained with the application of 0.16 kg each 45-O-O and 18-26-Oinorganic fertilizers per pond after each water replenishment. TABLE 2 Proximate analysis of the diets on dry-weight basis Nutrients (96) Moisture Crude protein Crude fat Crude fiber NFE Ash Calculated M.E. (kcal/ 100 g)
Diet I 7.7350.17 34.06 + 0.22 8.23f0.009 5.92+0.10 38~26 13.53f 1.04 378.00
Diet 2 11.03f.o.17 34.66 f 0.23 8.41+ 0.27 3.18+0.16 41.07 12.68f 0.07 393.00
A.T. TRIRO ET AL.
28
Data analysis The data were analyzed for mean body weight, weight gain, survival rate, net production, feed conversion ratio (FCR) and net cost of production per kg and were subjected to analysis of variance to compare treatment means and to Duncan’s multiple range test to determine the significance of the difference among treatment means (Gomez and Gomez, 1976 ). The following formulae were used for the analysis of the data: Weight gain = mean final weight - mean initial weight. Survival rate=total number of surviving prawns/total initial number of prawns x 100. Net production= total weight of surviving prawns- total initial weight of prawns. FCR = total amount of feed given/total gain in weight of prawns. Net cost of production per kg= total cost of production/net production in kg. RESULTS
Table 3 shows the results of the experiment using three different treatments in a modified extensive system of culturing prawns. Significant differences (P> 0.05 ) were noted between treatment means for mean body weight, weight gain, net production, and net cost of production/kg of prawns while difI’erences between treatment means for survival rate and FCR were not significant (P> 0.05 ). Duncan’s multiple range Test showed that mean body weights, weight gain, net production, and net cost of production/kg of prawns fed diets with and without vitamins were not significantly different but that they differed significantly from those of prawns not given supplemental feed. There were no considerable differences observed in water-quality parameters between and within treatments (Table 4). Water temperature, salinity TABLE 3
Growth, survival, FCR, net production and net cost of production of P. monodon on supplemental and con&cl diets. Average of three replicates for all treatments Treatment
Diet I Diet 2 Control
cv (96)
Mean Mean initial final weight weight
Mean weight gain
(6)
I%)
!o!
0.17 0.16 0.11
23.7f4.1*b 2;.;;;.:” ._,I
23.5f4.1Lb 21.9+4.5*b 7.4f2.6n
8.4
7.7
Survival WI
FCR
Net production (kg)
Net cost of production/kg I” .a (
73.6+ 5.8”’ 2.5+0.36”’ 63.8f 15.8”’ 2.9f0.55”” 51.4k27.7” -
27.1 +5.Yb 22.3f2.6*b 6.0 f 5.2”
115.63+25 OOeb 97.61 f 13:02” 42.45 f 20. 10s”
10.0
10.0
10.05
‘Significant at PC 0.05; ns - not significant at P< 0.05. Values with the same superscript are not significantly different.
5.5
EXTENSIVE f? MONODONCULTURE WITHOUT SUPPLEMENTAL VITAMINS
29
TABLE 4
Mean physico-chemical parameters observed in ponds for all treatments for the whole culture period. Average of three replicates Treatment
Water temperature
Water salinity
Dissolved oxygen
(“C)
(PPt)
(ppm)
Diet I Range Mean
26.2-26.4 26.3
3 1.9-32.0 31.9
3.9-4.0 3.9
7.0- 9.0
Diet 2 Range Mean
26.1-26.2 26.2
31.3-31.7 31.6
3.6-4.2 3.9
7.0-10.9 8.0
Control Range Mean
26.2-26.4 26.3
31.4-31.8 31.6
4.0-4.1 4.1
6.0- 9.0 8.0
Water PH
7.5
and dissolved oxygen were generally the same for all treatments. Water pH was generally alkaline. DISCUSSION
Natural food still comprises an important portion of the total food sources of prawns in MODEX. It supplies an appreciable amount of protein and other nutrients required by the prawns for the first few weeks. Supplemental feed becomes essential with increased prawn biomass. Since supplemented feed is one of the major inputs in production (Posadas, 1988 ), lowering feed cost is important in making MODEX profitable. The elimination of vitamin supplements from the diet is one way of reducing feed cost. Catacutan and de la Cruz ( 1989) have demonstrated that some water-soluble vitamins are dispensable in purified diets. Dickson ( 1987) concluded that vitamin premix in the diet is not economically justifiable in intensive tilapia farming since its inclusion did not result in improved growth rates or food conversion. Likewise, Castille and Lawrence ( 1989 ) found that elimination of vitamins from pelleted feeds did not affect the growth of Penaeus vannamei reared for 28 days in pens and suggested that vitamin supplementation is not necessary when natural foods are present in ponds. Results of this study indicate that growth, survival, net production, and net cost of production per kg of P. monodon in the treatment with diet 2 that contained no vitamin supplemtint were not significantly affected. This observation is consistent with the reports about some other species by the authors cited above. In contrast, Catacutan and de la Cruz ( 1989) reported that p. monodonfed the no-vitamin diet had the poorest growth rate. The absence of
30
A.T. TRIRO ET AL.
vitamins in the diet has, therefore, serious effects on growth and survival of prawns. However, dietary requirements for vitamins in prawns and other animals are low and deficiencies in the diet could be compensated from several other sources (Morrison, 1957; Phillips, 1984). For instance, the poor growth performance of prawns on the no-vitamin diet (Catacutan and de la CNZ, 1989) may have been the consequence of relying entirely on artificial diets since the prawns were reared in tanks with filtered seawater. The prawns in our study had the pond ecosystem as source of natural food and received a supplemental diet as well. Studies by Rubright ( 1978 ) and Rubright et al. ( 198 1) revealed that crustaceans, copepods, polychaetes, and nematodes were some of the important natural food components of the pond ecosystem in their experiments. The same organisms plus the chironomid larvae were abundant in all ponds in our study 5 days before and for 60 days after stocking; thereafter, their numbers declined throughout the culture period, possibly indicating prawn grazing during that time. Rubright et al. ( 198 1) attributed an increase in shrimp production in fertilized and feed ponds to the abundant occurrence of polychaetes, copepods, and nematodes. This was implicitly confirmed by Anderson et al. ( 1987 ) when they showed that, when natural foods are abundant, between 53 and 77% of the growth of fenaeus vunnamei is due to grazing on pond biota while 23 to 47% is supplied by added feed. Crustaceans, copepods, polychaetes, and nematodes are the main diet of Penaeus species from the wild (Wassenberg and Hill, 1987) and their importance as nutritious food sources for marine invertebrates, from a standpoint of energy/protein and essential nutrient requirements, was pointed out by Phillips ( 1984). The absence of,added vitamins from the diet may have been compensated by many of the feedstuffs used since these are potential sources of vitamins. However, vitamins are heat-labile and are destroyed by light; hence, it was possible that vitamins in these feedstuffs were destroyed or lost during processing and storage. Sedgwick ( 1980) has ascribed the loss of vitamins in his formulation based on freeze-dried mussel meal on processing and immersion in water. If this was the case in our experiment, and considering that prawns seem to graze more natural than artificial food when both are available (Anderson et al., 1987), it is possible that the vitamin content of the basal diet was insufficient for the needs of the prawns and that the absence of a vitamin supplement in the diet was compensated by natural food occurring in the ponds. The present study was not designed to measure the specific level of each vitamin required by prawns. No analysis was made of the various vitamins in the diet nor of the extent to which they were available from natural food sources. Hence, the possible influence of vitamins from these sources is manifest only in the overall effects on growth, survival and net production of Prawns when the vitamin supplement is elizninated from the diet. The re-
EXTENSIVE f. MONODONCULTURE
WITHOUTSUPPLEMENTAL
VITAMINS
31
quirement for each vitamin and the level of intake from natural food sources have to be studied further. Analysis of the cost of production/kg for all treatments shows the control treatment to be by far the least costly. However, the mean final weight of the product will cause it to be rejected on the export market (DA-BOI, 1990) and to be less valued on the domestic market. Diet 2 without vitamin supplement thus remains the best treatment from the standpoint of economic production. The differences with diet 1 in relative growth performance, survival, net production, and net cost of production/kg of prawns produced are statistically non-significant, but its favorable cost difference of P 18.02/kg product would make it more profitable to use in a modified extensive culture system. ACKNOWLEDGEMENTS
We thank Dr. R. Coloso for editing the manuscript. The suggestions and advice of Dr. F.P. Pascual during and after the preparation of this study and the assistance of Mr. Jerry Babiera are gratefully acknowledged.
REFERENCES Anderson, R.K., Parker, P.L. and Lawrence, A.L., 1987. A i3C/‘* tracer study of the utilization of presented feed by a commercially important shrimp Penaeus vunnumeiin a pond growout system. J. World Aquacult. Sot., 18( 3): 148-155. AOAC (Associatio,:of Official Analytical Chemists), 1984. Official Methods of Analysis, 14th edn. AOAC, Arlington, VA, I 141 pp. Castille, EL. and Lawrence, A.L., 1989. The effects of deleting dietary constituents from pelleted feeds on the growth of shrimps in the presence of natural food in ponds. J. World Aquacult. Sot., 20( 1): 22A. Catacutan, M. and Cruz, M. de la, 1989. Growth and midgut cells profile of Penaeus monodon juveniles fed water-soluble vitamin-deficient diets. Aquaculture, 8 1: 137-I 44. DA-B01 (Department of Agriculture-Board of Investment, Philippines), 1990. I989 World shrimp performance. Fish Talk, l(2): i-9. Deshimaru, 0. and Kuroki, K., 1974. Studies on purified diet. 1. Basal composition of diet. Bull. Jpn. Sot.. Sci. Fish.,,40: 413-419. Dickson, M.W., 1987. The supply of vitamins in feed for intensive tilapia farming in Zambia. Aquacult. Fish. Manage., 18(2): 221-230. Gomez, K.A. and Gomez, A.A., 1976. Statistical Procedures for Agriculture! Research with Emphasis on Rice. The International Rice Research Institute, Los Bafios, Laguna, The Philippines, 294 pp. Morrison, F.B., 1957. Feeds and Feeding, 22nd edn. Cornell University Press, Ithaca, NY, I 165 : PP. Pascual, F.P., 1983. Nutrition and Feeding of Penaeus monodon, 3rd edn. Extension Manual No. 2. SEAFDEC Aquaculture Department, Iloilo, Philippines, I8 pp. (unpublished ). Pascual, F.P. and Catacutan, M., 1990. Defatted soybean meal and leucaena leafmeal as protein sources in diets for Penueus monodonjuveniles. In: R. Hirano and I. Hanyu (Editors), Pro-
32
A.T. TRI6JO ET AL.
ceedings of the Second Asian Fisheries Forum, 17-22 April 1989, Tokyo, Japan. Asian Fisheries Society, Manila, Philippines, pp. 345-348. Phillips, N.W., 1984. Role of different microbes and substrates as potential suppliers of specific, essential nutrients to marine detritivores. Bull. Mar. Sci., 35( 3): 283-298. Posadas, B.C., 1988. Economic analysis of various prawn farming systems. In: Y.N. Chiu, L.M. Santos and R.O. Juliano (Editors), Technical Considerations for the Management and Operations of Intensive Prawn Farms. U.P. Aquaculture Society, Iloilo City, Philippines, pp. 12-24. Rubright, J-S., 1978. An investigation into the role of meiofauna in the food chain of a shrimp mariculture pond system. M.S. Thesis, Texas A&M Univ., College Station, TX, USA. Rubright, J.S., Harrell, J.L., Holcomb, H.W. and Parker, J.C., 1981. Response of planktonic and benthic communities to fertilizer and feed applications in shrimp mariculture ponds. J. World Maricult. Sot., 12 ( 1): 28 l-299. Sedgwick, R.W., 1980. The requirements of Penaeus merguiensis for vitamin and mineral supplements in diets based on freeze-dried Myfilusedulis meal. Aquaculture, 19: 127- I 37. Wassenberg, T.J. and Hill, B.J., 1987. Natural diet of the tiger prawns Peitaeus esculenlus and P. semisufcutus.Aust. J. Mar. Freshwater Res., 38: 169-l 82.
25
Growth and survival of Penaeus monodon juveniles fed a diet lacking vitamin supplements in a modified extensive culture system Avelino T. Triiio, Veronica D. Pefiaflorida and Edna C. Bolivar AquacultureDepartment,SoutheastAsian FisheriesDevelopmentCenter, P.O. Box 256, Iloilo, Philippines (Accepted I6 April 199I )
ABSTRACT Trifio, A.T., Peiiaflorida, V.D. and Bolivar, E.C., 1992. Growth and survival of Penaeus monodon juveniles fed a diet lacking vitamin supplements in a modified extensive culture system. Aq:z.wulture, 101: 25-32. Penaeusmonodon juveniles with mean initial weight from 0.1 I to 0. I7 g were fed diets with and without vitamin supplement. The diets contained 34Ohprotein and 8% fat. The animals were stocked at 5/m* in 320-m* earthen ponds and reared for 135 days. Growth, survival, net production, and net cost of production per kg of P. monodon were not significantly affected even if supplemental vitamins were eliminated from the diet. The absence of extra vitamins from the diet may have been compensated either by the basal diet used or by ingestion of natural food existing in the ponds. In either case, the possible influence of vitamins from these sources is manifested in the overall effects on growth, survival and net production of prawns when no vitamin supplement is added to the diet. Results obtained showed that the difference between diets in cost of production was statistically not significant (P> 0105). However, the favorable cost difference of P 18.02 per kg of prawns produced would make it more profitable to use the diet without vitamin supplement in a modified extensive culture system.
INTRODUCTION
The slump in the export market of P. monodon has caused some fish-farm operators to shift from an intensive to a modified extensive system (MODEX ) of culturing prawns. Comparative economic analysis of the different prawn culture systems (Posadas, 1988 ) indicates that under existing market conditions, MODEX becomes economically profitable only if the cost of production is lowered. One way of reducing cost is through feed inputs since those contribute 55% to production costs (Posadas, 1988 ). Elimination of the extra vitamins from the diet will give substantial savings in feed cost of approximately P lO.OO/kg (Pascual and Catacutan, 1990) 0044-8486/92/$05.00
0 1992 Elsevier Scierce Publishers B.V. All rights reserved.
A.T. TRIRO ET AL.
26 TABLE 1 Composition and cost per kg of the diets Ingredients (%)
Diet 1
cost (P)
Diet 2
cost (P)
Tuna-fish meal Prawn-head meal Soybean meal, defatted Rice bran Wheat gluten Bread flour Cod-liver oil Soybean oil Lecithin Mineral mix’ Vitamin mix’ Propionic acid BHT
16 15 35 12 3 10.7 1.5 2 1.5 1.5 0.1 0.2
2.56 1.50 1.28 0.42 2.27 1.07 1.20 0.75 2.20 10.50 10.50 0.11 0.16
16 15 35 12 3 12.2 1.5 1.5 2 1.5 0.0 0.1 0.2
2.56 1.50 1.28 0.42 2.27 1.22 1.20 0.75 2.20 10.50 0.00 0.11 0.16
Subtotal Processing and bagging Total
100.00
34.52 --10.53 45.02
100.00
24.17 10.50 34.67
‘For compositio n of mineral and vitamin mixes see Deshimaru and Kuroki ( 1974).
compared to the same diet with vitamin supplement (Table 1). Although vitamins are essential food constituents in the diet, they may also be provided by plant and animal food organisms endemic in ponds. Under MODEX these food organisms are grown during pond preparation and maintained for the whole culture period to serve as natural food base for the prawns. This study was undertaken to determine the growth and survival of P. monodon when fed a diet without vitamin supplement under a modified extensive culture system. MATERIALS AND METHODS
Design of experiment The study was conducted for 135 days in nine 32-m* ponds at the Leganes Brackishwater Station, Iloilo, The Philippines. Three replicates were assigned in a randomized complete block design (RCBD) using the following treatments: supplemental diet I (with vitamin supplement ); supplemental diet 2 (without vitamin supplement ); control (without supplemental feeding). Prawn fry ( PL20) with mean initial weight from 0.11 to 0.17 g were obtained from the prawn hatchery at SEAFDEC AQD Tigbauan Research Station. The fry were brought in aerated plastic bags when the ponds were ready for stocking. Animals were weighed before stocking and subsequently weighed every 15 days.
EXTENSlVEP.MONODONCULTUREWITHOUTSUPPLEMENTALVITAMINS
27
Pond preparation
The ponds were prepared to induce growth of plankton to serve as natural food base for the prawns. Pond preparation consisted of letting the pond bottom dry for 1 week, applying hydrated lime at 32 kg/pond and filling the pond with water to a depth of 30 cm. Fertilization was done with chicken manure and inorganic fertilizers. Chicken manure was applied at 32 kg/pond, equally divided in two plastic sacks and suspended at opposite sides of the pond. A 1: 1 ratio of inorganic fertilizers (45-O-Oand 18-26-o) were broadcasted at 1.28 kg/pond. Upon development of luxuriant growth of plankton (pond water turned light brown in 5 days) the pond-water level was raised to 60 cm. Stocking was then carried out after 3 days. Diets
Two supplemental diets were formulated (Table 1) to contain around 34% protein and 8% fat (Table 2). Diet 1 had extra vitamins while diet 2 had none. The other ingredients were the same in both diets except for bread flour ( 10.7% for diet 1 and 12.2% for diet 2). The amount of bread flour was altered to compensate for the eliminated vitamins. The difference in calculated M.E. between the two diets was only 15 kcal/ 100 g (Table 2). The diets were prepared following the procedures of Pascual ( 1983 ) . The proximate analysis of the diets was performed at SEAFDEC AQD Centralized Analytical Laboratory using standard methods ( AOAC, 1984). Culture management
The prawns were stocked at five individuals/m’ after acclimation to pondwater temperature and salinity. Water depth was maintained at 60 cm for the first month and gradually increased to I m thereafter. Every spring tide about 30% of the pond water was replenished once a day for 3 consecutive days. Plankton growth was maintained with the application of 0.16 kg each 45-O-O and 18-26-Oinorganic fertilizers per pond after each water replenishment. TABLE 2 Proximate analysis of the diets on dry-weight basis Nutrients (96) Moisture Crude protein Crude fat Crude fiber NFE Ash Calculated M.E. (kcal/ 100 g)
Diet I 7.7350.17 34.06 + 0.22 8.23f0.009 5.92+0.10 38~26 13.53f 1.04 378.00
Diet 2 11.03f.o.17 34.66 f 0.23 8.41+ 0.27 3.18+0.16 41.07 12.68f 0.07 393.00
A.T. TRIRO ET AL.
28
Data analysis The data were analyzed for mean body weight, weight gain, survival rate, net production, feed conversion ratio (FCR) and net cost of production per kg and were subjected to analysis of variance to compare treatment means and to Duncan’s multiple range test to determine the significance of the difference among treatment means (Gomez and Gomez, 1976 ). The following formulae were used for the analysis of the data: Weight gain = mean final weight - mean initial weight. Survival rate=total number of surviving prawns/total initial number of prawns x 100. Net production= total weight of surviving prawns- total initial weight of prawns. FCR = total amount of feed given/total gain in weight of prawns. Net cost of production per kg= total cost of production/net production in kg. RESULTS
Table 3 shows the results of the experiment using three different treatments in a modified extensive system of culturing prawns. Significant differences (P> 0.05 ) were noted between treatment means for mean body weight, weight gain, net production, and net cost of production/kg of prawns while difI’erences between treatment means for survival rate and FCR were not significant (P> 0.05 ). Duncan’s multiple range Test showed that mean body weights, weight gain, net production, and net cost of production/kg of prawns fed diets with and without vitamins were not significantly different but that they differed significantly from those of prawns not given supplemental feed. There were no considerable differences observed in water-quality parameters between and within treatments (Table 4). Water temperature, salinity TABLE 3
Growth, survival, FCR, net production and net cost of production of P. monodon on supplemental and con&cl diets. Average of three replicates for all treatments Treatment
Diet I Diet 2 Control
cv (96)
Mean Mean initial final weight weight
Mean weight gain
(6)
I%)
!o!
0.17 0.16 0.11
23.7f4.1*b 2;.;;;.:” ._,I
23.5f4.1Lb 21.9+4.5*b 7.4f2.6n
8.4
7.7
Survival WI
FCR
Net production (kg)
Net cost of production/kg I” .a (
73.6+ 5.8”’ 2.5+0.36”’ 63.8f 15.8”’ 2.9f0.55”” 51.4k27.7” -
27.1 +5.Yb 22.3f2.6*b 6.0 f 5.2”
115.63+25 OOeb 97.61 f 13:02” 42.45 f 20. 10s”
10.0
10.0
10.05
‘Significant at PC 0.05; ns - not significant at P< 0.05. Values with the same superscript are not significantly different.
5.5
EXTENSIVE f? MONODONCULTURE WITHOUT SUPPLEMENTAL VITAMINS
29
TABLE 4
Mean physico-chemical parameters observed in ponds for all treatments for the whole culture period. Average of three replicates Treatment
Water temperature
Water salinity
Dissolved oxygen
(“C)
(PPt)
(ppm)
Diet I Range Mean
26.2-26.4 26.3
3 1.9-32.0 31.9
3.9-4.0 3.9
7.0- 9.0
Diet 2 Range Mean
26.1-26.2 26.2
31.3-31.7 31.6
3.6-4.2 3.9
7.0-10.9 8.0
Control Range Mean
26.2-26.4 26.3
31.4-31.8 31.6
4.0-4.1 4.1
6.0- 9.0 8.0
Water PH
7.5
and dissolved oxygen were generally the same for all treatments. Water pH was generally alkaline. DISCUSSION
Natural food still comprises an important portion of the total food sources of prawns in MODEX. It supplies an appreciable amount of protein and other nutrients required by the prawns for the first few weeks. Supplemental feed becomes essential with increased prawn biomass. Since supplemented feed is one of the major inputs in production (Posadas, 1988 ), lowering feed cost is important in making MODEX profitable. The elimination of vitamin supplements from the diet is one way of reducing feed cost. Catacutan and de la Cruz ( 1989) have demonstrated that some water-soluble vitamins are dispensable in purified diets. Dickson ( 1987) concluded that vitamin premix in the diet is not economically justifiable in intensive tilapia farming since its inclusion did not result in improved growth rates or food conversion. Likewise, Castille and Lawrence ( 1989 ) found that elimination of vitamins from pelleted feeds did not affect the growth of Penaeus vannamei reared for 28 days in pens and suggested that vitamin supplementation is not necessary when natural foods are present in ponds. Results of this study indicate that growth, survival, net production, and net cost of production per kg of P. monodon in the treatment with diet 2 that contained no vitamin supplemtint were not significantly affected. This observation is consistent with the reports about some other species by the authors cited above. In contrast, Catacutan and de la Cruz ( 1989) reported that p. monodonfed the no-vitamin diet had the poorest growth rate. The absence of
30
A.T. TRIRO ET AL.
vitamins in the diet has, therefore, serious effects on growth and survival of prawns. However, dietary requirements for vitamins in prawns and other animals are low and deficiencies in the diet could be compensated from several other sources (Morrison, 1957; Phillips, 1984). For instance, the poor growth performance of prawns on the no-vitamin diet (Catacutan and de la CNZ, 1989) may have been the consequence of relying entirely on artificial diets since the prawns were reared in tanks with filtered seawater. The prawns in our study had the pond ecosystem as source of natural food and received a supplemental diet as well. Studies by Rubright ( 1978 ) and Rubright et al. ( 198 1) revealed that crustaceans, copepods, polychaetes, and nematodes were some of the important natural food components of the pond ecosystem in their experiments. The same organisms plus the chironomid larvae were abundant in all ponds in our study 5 days before and for 60 days after stocking; thereafter, their numbers declined throughout the culture period, possibly indicating prawn grazing during that time. Rubright et al. ( 198 1) attributed an increase in shrimp production in fertilized and feed ponds to the abundant occurrence of polychaetes, copepods, and nematodes. This was implicitly confirmed by Anderson et al. ( 1987 ) when they showed that, when natural foods are abundant, between 53 and 77% of the growth of fenaeus vunnamei is due to grazing on pond biota while 23 to 47% is supplied by added feed. Crustaceans, copepods, polychaetes, and nematodes are the main diet of Penaeus species from the wild (Wassenberg and Hill, 1987) and their importance as nutritious food sources for marine invertebrates, from a standpoint of energy/protein and essential nutrient requirements, was pointed out by Phillips ( 1984). The absence of,added vitamins from the diet may have been compensated by many of the feedstuffs used since these are potential sources of vitamins. However, vitamins are heat-labile and are destroyed by light; hence, it was possible that vitamins in these feedstuffs were destroyed or lost during processing and storage. Sedgwick ( 1980) has ascribed the loss of vitamins in his formulation based on freeze-dried mussel meal on processing and immersion in water. If this was the case in our experiment, and considering that prawns seem to graze more natural than artificial food when both are available (Anderson et al., 1987), it is possible that the vitamin content of the basal diet was insufficient for the needs of the prawns and that the absence of a vitamin supplement in the diet was compensated by natural food occurring in the ponds. The present study was not designed to measure the specific level of each vitamin required by prawns. No analysis was made of the various vitamins in the diet nor of the extent to which they were available from natural food sources. Hence, the possible influence of vitamins from these sources is manifest only in the overall effects on growth, survival and net production of Prawns when the vitamin supplement is elizninated from the diet. The re-
EXTENSIVE f. MONODONCULTURE
WITHOUTSUPPLEMENTAL
VITAMINS
31
quirement for each vitamin and the level of intake from natural food sources have to be studied further. Analysis of the cost of production/kg for all treatments shows the control treatment to be by far the least costly. However, the mean final weight of the product will cause it to be rejected on the export market (DA-BOI, 1990) and to be less valued on the domestic market. Diet 2 without vitamin supplement thus remains the best treatment from the standpoint of economic production. The differences with diet 1 in relative growth performance, survival, net production, and net cost of production/kg of prawns produced are statistically non-significant, but its favorable cost difference of P 18.02/kg product would make it more profitable to use in a modified extensive culture system. ACKNOWLEDGEMENTS
We thank Dr. R. Coloso for editing the manuscript. The suggestions and advice of Dr. F.P. Pascual during and after the preparation of this study and the assistance of Mr. Jerry Babiera are gratefully acknowledged.
REFERENCES Anderson, R.K., Parker, P.L. and Lawrence, A.L., 1987. A i3C/‘* tracer study of the utilization of presented feed by a commercially important shrimp Penaeus vunnumeiin a pond growout system. J. World Aquacult. Sot., 18( 3): 148-155. AOAC (Associatio,:of Official Analytical Chemists), 1984. Official Methods of Analysis, 14th edn. AOAC, Arlington, VA, I 141 pp. Castille, EL. and Lawrence, A.L., 1989. The effects of deleting dietary constituents from pelleted feeds on the growth of shrimps in the presence of natural food in ponds. J. World Aquacult. Sot., 20( 1): 22A. Catacutan, M. and Cruz, M. de la, 1989. Growth and midgut cells profile of Penaeus monodon juveniles fed water-soluble vitamin-deficient diets. Aquaculture, 8 1: 137-I 44. DA-B01 (Department of Agriculture-Board of Investment, Philippines), 1990. I989 World shrimp performance. Fish Talk, l(2): i-9. Deshimaru, 0. and Kuroki, K., 1974. Studies on purified diet. 1. Basal composition of diet. Bull. Jpn. Sot.. Sci. Fish.,,40: 413-419. Dickson, M.W., 1987. The supply of vitamins in feed for intensive tilapia farming in Zambia. Aquacult. Fish. Manage., 18(2): 221-230. Gomez, K.A. and Gomez, A.A., 1976. Statistical Procedures for Agriculture! Research with Emphasis on Rice. The International Rice Research Institute, Los Bafios, Laguna, The Philippines, 294 pp. Morrison, F.B., 1957. Feeds and Feeding, 22nd edn. Cornell University Press, Ithaca, NY, I 165 : PP. Pascual, F.P., 1983. Nutrition and Feeding of Penaeus monodon, 3rd edn. Extension Manual No. 2. SEAFDEC Aquaculture Department, Iloilo, Philippines, I8 pp. (unpublished ). Pascual, F.P. and Catacutan, M., 1990. Defatted soybean meal and leucaena leafmeal as protein sources in diets for Penueus monodonjuveniles. In: R. Hirano and I. Hanyu (Editors), Pro-
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ceedings of the Second Asian Fisheries Forum, 17-22 April 1989, Tokyo, Japan. Asian Fisheries Society, Manila, Philippines, pp. 345-348. Phillips, N.W., 1984. Role of different microbes and substrates as potential suppliers of specific, essential nutrients to marine detritivores. Bull. Mar. Sci., 35( 3): 283-298. Posadas, B.C., 1988. Economic analysis of various prawn farming systems. In: Y.N. Chiu, L.M. Santos and R.O. Juliano (Editors), Technical Considerations for the Management and Operations of Intensive Prawn Farms. U.P. Aquaculture Society, Iloilo City, Philippines, pp. 12-24. Rubright, J-S., 1978. An investigation into the role of meiofauna in the food chain of a shrimp mariculture pond system. M.S. Thesis, Texas A&M Univ., College Station, TX, USA. Rubright, J.S., Harrell, J.L., Holcomb, H.W. and Parker, J.C., 1981. Response of planktonic and benthic communities to fertilizer and feed applications in shrimp mariculture ponds. J. World Maricult. Sot., 12 ( 1): 28 l-299. Sedgwick, R.W., 1980. The requirements of Penaeus merguiensis for vitamin and mineral supplements in diets based on freeze-dried Myfilusedulis meal. Aquaculture, 19: 127- I 37. Wassenberg, T.J. and Hill, B.J., 1987. Natural diet of the tiger prawns Peitaeus esculenlus and P. semisufcutus.Aust. J. Mar. Freshwater Res., 38: 169-l 82.