Evaluation of different sources of lipid and lipid levels in the diet of pearlspot Etroplus suratensis (Teleostei: Perciformes)

Transcription

1 Indian Journal of Marine Sciences Vol. 33(3), September 2004, pp Evaluation of different sources of lipid and lipid levels in the diet of pearlspot Etroplus suratensis (Teleostei: Perciformes) *S Ahamad Ali Central Institute of Brackishwater Aquaculture, Chennai , India *[ Received 27 May 2003; revised 9 March 2004 Seven different s namely, coconut, cod liver, gingely (sesame seed), groundnut, sunflower, soybean and sardine were evaluated in the diet of pearlspot (Etroplus suratensis). These s were individually incorporated at 7% level in an iso-nitrogenous diet consisting of a protein base, other ingredients and binder. In the second experiment, a mixture of coconut and sardine (which gave the best results in the first experiment) in the ratio of 1 : 1 was prepared to study the effect of dietary lipid levels on growth of pearlspot. Seven more iso-nitrogenous diets were formulated with the above mixed lipid supplementation of 0 to 15%.The results of the 35-day feeding trial with test diets having different lipid sources showed that the fish (initial weight g) fed with diet containing coconut led to significantly (P<0.05) higher weight gain of 23.91±1.92 g followed by the diets with sardine (19.2±0.89 g), cod liver (19.15±1.24 g), gingely (16.52±0.66 g) and the control diet led to a weight gain of 19.24±0.59 g. The specific growth rate also followed similar trend. The weight gain of fish fed with diets having groundnut, sunflower and soybean is marginally less than that of the control diet indicating that dietary addition of these s had no beneficial effect on growth. The diet with coconut led to significantly (P<0.05) lower FGR (1.60) followed by that containing cod liver (1.96) and sardine (2.0). The growth of fish increased, feed gain ratio (FGR) and protein efficiency ratio (PER) improved with increase in lipid supplementation in the diet up to 5%. The diet with a total lipid content of 8.6%(with 5% supplementation) gave significantly (P<0.05) higher weight gain (18.24±0.84 g), specific growth rate (1.0590) and lowest FGR (1.6). This diet also gave significantly (p<05) better PER (1.94). Further increase in the lipid supplementation in diet had negative effect on growth, SGR, FGR and PER. The results obtained in this study can be utilized for formulating practical feeds using appropriate lipid sources for feeding pearlpsot for its aquaculture. This study also leads to further investigations on more specific dietary fatty acid requirements of Etroplus suratensis. [Key words: Lipid, diet, pearlspot, growth, feed gain ratio, Etroplus suratensis, fatty acids] [IPC Code: Int. Cl 7. A23L 1/30] Introduction The finfish Etroplus suratensis (Bloch)(Teleostei: Perciformes) commonly known as pearlspot, belongs to the family Cichlidae. It is euryhaline and inhabits the backwater areas of coastal states in India. Pearlspot is a highly preferred food fish and because of this there is a good demand for aquaculture of this species. Determination of dietary requirements for developing balanced feeds is an important prerequisite for aquaculture of this fish. There had been a few studies in this direction where the use of formulated diets and dietary requirement of protein were studied 1-3. In the present study, an attempt is made to evaluate different sources of lipids and lipid levels in the diet of pearlspot. Material and Methods Seven different s namely, coconut (refined), cod liver (Seven Seas brand), gingely (sesame seed) (refined), groundnut (refined), sunflower (refined), soybean (refined) and sardine (extracted by hydraulic press and filtered) were evaluated in the diets of pearlspot (Etroplus suratensis). The s (reputed brands) were purchased from the market (contain permitted anti-oxidant) and used as such. These s were individually incorporated at 7% level in an iso-nitrogenous diet (5.2% N) consisting of protein base made of fishmeal, prepared by pulverizing assorted dry fish (CP 54%), groundnut cake (CP 40%) and wheat bran (CP 9%). The lipid content of fishmeal prepared from the mixed fish varied (6 to 13%) from batch to batch, hence the difference in lipid content of control diets of first and second experiments as the fishmeal used was from two different batches. The other ingredients in the diet were tapioca flour, vitamin mix, mineral mix and binder (carboxymethyl cellulose). The control diet was formulated

2 282 INDIAN J. MAR. SCI., VOL. 33, NO. 3, SEPTEMBER 2004 without adding any and the crude fat content was about 6%. The composition of the test diets 1-8 is given in Table 1. In the second experiment a mixture of coconut and sardine (which gave the best results in the first experiment) in the ratio of 1 : 1 was prepared to study the effect of lipid levels in diet on pearlspot. Seven more iso-nitrogenous diets (9-15) were formulated with lipid supplementation of 0 to 15% and their composition is given in Table 2. The solid ingredients were powdered in an electrical grinder and passed through 0.5 mm sieve. The diets were mixed as per the formulation and homogenized thoroughly in an electrical blender. The binder was dissolved in hot water (40 ml for 100 g diet) and added to the diet mix and kneaded into dough. It was steamed for five minutes at atmospheric pressure (in a pressure cooker without weight) and cooled. The diet was stored in a refrigerator and used for feeding the experimental fish. Pearlspot juveniles collected from the backwaters of Narakkal Research Center of CIBA were grouped into uniform size as far as possible and acclimatized in the laboratory tanks for one week before start of the experiment. Twenty fish were stocked in plastic lined circular pools ( m diameter height) with three replicates for each treatment.the fish were fed semimoist diet (at 10% of their body weight calculated on dry weight of feed after estimating the moisture) in the morning and evening. The rate of feeding was regulated as per the consumption indicated by the leftover feed. The sediments in tanks were removed regularly after collecting the leftover feed. After drying the leftover feed it was weighed and subtracted from the feed offered to calculate feed consumption and FGR.The water level was maintained by replacement daily. Total water was replaced in the tanks once in five days.the duration of the feeding experiment was 35 days. During the experiment the water in the tanks had a salinity of 10.4 ± 2.0, dissolved oxygen 5.1±0.2 cc/l, ph 7.8±0.3 and temperature 25.8±1.0 C. Different growth parameters calculated are given below: Specific Growth Rate: log W 1 (final weight) log W 0 (initial weight) 100 Time in days (duration of experiment) Table 1 Composition of test diets with different lipid sources for pearlspot (Etroplus suratensis) Diet No. Ingredients Protein base* Coconut Cod liver Groundnut Gingely Sunflower Soybean Sardine Tapioca flour Vitamin mix.** Mineral mix.*** Binder (CMC) Proximate composition (% on dry matter basis) Crude Protein Lipid NFE Crude fiber Total Ash Moisture *Protein base: Fish meal (CP 54%)= 54.0g, Groundnut cake (CP 40%) = 9.0g and Wheat bran (CP 9%) = 8.0g **Vitamin mixture: 100 g diet contained Vitamin A (acetate) 700 I.U., Vitamin D3 300 I.U.,Vitamin E 12 mg, Vitamin K 5 mg, Thiamine HCl 4 mg, Riboflavin 6 mg, Calcium pantothenate 20 mg, Biotin 0.05 mg, Folic acid 2 mg, Cyanocobalamine 0.02 mg, Niacin 30 mg, Pyridoxine 4 mg, Inositol 50 mg, Ascorbic acid 50 mg, Choline chloride 600 mg. ***Mineral mixture (g/100g diet): Calcium carbonate 1.8, Potassium dihydrogen orthophosphate 1.21, Ferric citrate 0.39, Manganous sulphate 0.21, Zinc sulphate 0.29, Magnesium sulphate 0.59, Potassium iodide 0.01

3 AHAMAD ALI: DIET OF PEARLSPOT (Etroplus Suratensis) 283 Table 2 Composition of test diets with different lipid levels for evaluation on Pearlspot Etroplus suratensis Diet No. Ingredients Basal diet mix Lipid mix Tapioca flour Vitamin mix* Mineral mix** Binder (CMC) Proximate composition (% on dry matter basis) Crude protein Ether extract NFE Crude fiber Ash Moisture Basal diet mixture: for 100 g diet fish meal 54.0 g, groundnut cake 9.0 g and wheat bran 8.0 g 2 Lipid mix:coconut and sardine in 1 : 1 ratio * Vitamin mix and Mineral mix same as in diets 1 to 8 in Table 1 Weight gain=final average wt initial average wt Feed Gain Ratio (FGR) = Protein Efficiency Ratio Feed consumed in dry weight Increase in live weight Average weight gain (g) = Protein consumed (g) The diets were analyzed for crude protein, fat, ash, crude fiber and moisture by following AOAC 4 methods and the nitrogen free extract (NFE) was calculated by difference of total from 100. Results on increase in weight, FGR and PER were subjected to ANOVA 5 and the means were compared by the critical difference method. Results and Discussion The results of the feeding trial with test diets (1 8) having different lipid sources (Table 3) show that the fish fed with diet containing coconut led to significantly (P<0.05) higher weight gain (23.91±1.92 g), followed by the diets with sardine (19.2±0.89 g), cod liver (19.15±1.24 g), gingely (16.52±0.66 g) and the control diet led to weight gain of 19.24±0.59 g. The specific growth rate also followed the same trend. The growth of fish fed with diets having groundnut, sunflower and soybean is marginally less (around 15%) than that of the control diet. The diet with coconut led to significantly (P<0.05) lower FGR (1.60) followed by that of cod liver (1.96) and sardine (2.0). The other diets showed higher FGR values than that of the control diet. The coconut, which is having higher melting point and rich in saturated fatty acids (16:0) led to better growth and FGR in pearlspot a warm water species compared to the PUFA rich s. At the same time sardine and cod liver, which are rich in polyunsaturated fatty acids followed coconut in performance. However, the other s, especially sunflower and soybean, which are predominantly rich in n-6 fatty acids did not show good performance as sardine and cod liver, suggesting that diets with high n-6 fatty acids may give poor growth. Coconut has 87.9% of saturated fatty acids and 8.6% of unsaturated fatty acids representing 7.8% of 18:1n-9 and 0.8% of 18:2n-6 6. Perhaps pearlspot prefers monoenoic fatty acid in its diet. Although, gingely, groundnut, soybean and sunflower s have high amounts of 18:1n-9, they are also rich in 18:2n-6 6. The performance of diets supplemented with these s indicates

4 284 INDIAN J. MAR. SCI., VOL. 33, NO. 3, SEPTEMBER 2004 Table 3 Results of feeding trials with test feeds 1 8 on pearlspot for 35 days Oil source No addition Coconut Cod liver Test Feeds (1 8) Groundnut Gingely Sunflower Soybean Sardine Initial average weight (g) (+SD) Final average weight (g)(+sd) Average weight gain (g) (+SD) Specific growth rate (+SD) ± ± b ± ± ± ± a ± ± ± ± b ± ± ± ± c ± ± ± ± d ± ± ± ± dc ± ± ± ± dc ± ±0.076 FGR 3.20 b 1.60 a 1.96 a 3.60 b 4.00 c 4.10 c 3.20 b 2.00 a Survival (%) ANOVA EMS SE CD (0.05) Weight gain FGR Values with different superscript differ significantly (P<0.05) among themselves ± ± b ± ±0.045 that a higher level of n-6 fatty acid (linoleic acid) seems to be not desirable to pearlspot. The performance of diets with sardine and cod liver that are rich in PUFA and HUFA (n-3 fatty acids) is also not significantly different from that of coconut. This indicates that lipids rich in n-3 fatty acids are preferable to those rich in n-6 fatty acids.the requirement for n-3 fatty acids for pearlspot may be low. As all the test diets had basic lipid component derived from fishmeal (powdered dry fish), the low requirement of n-3 fatty acids might have been met. More prolonged feeding experiments may be required to establish the requirement of n-3 fatty acids for pearlspot as in the case of common carp 7. Pearlspot, though euryhaline, tends to dwell and grow better in low saline to freshwater conditions. Probably it is this factor, which points out to the fatty acid needs of pearlspot.warm water fish species such as tilapia requires n-6 fatty acids more than that n-3 fatty acids 8. It is the case with Indian major carps 9. Shiranee & Natarajan 2 while testing three feeds for pearlspot in pond culture experiment reported that fish fed with diet fortified with a mixture of fish liver and palm (in 1:4 ratio) did not grow as well as the fish fed with diet not fortified with the s.subsequently Shiranee & Natarajan 10 studied the effect of same mixture on ovarian development and maturation of pearlspot and suggested that this mixed supplementation had positive results but however, attributed the same due to carotenoids and tocopherol in palm rather than to its fatty acid profiles. Similar observations were made in another cichlid tilapia by Viola et al. 11 and Viola & Arieli 12 in which it was reported that seven months of exposure of tilapia to PUFA had little effect on growth and body composition of the fish. The results of the present study are in line with these investigations wherein they do not indicate any clear trends of fatty acid requirements of pearlspot, hence it is suggested that more studies are needed to determine the dietary requirement of specific fatty acids for this fish. Good performance of coconut in fish diets is not uncommon as in the case of pearlspot in the present study.guillou et al. 13 reported that the growth of brook charr (Salvelinus fontinalis) fed with coconut diet was comparable to those fed with soybean and menhaden. Similarly, Fortagne et al. 14 observed that common carp larvae were capable of efficiently utilizing dietary coconut with excellent survival of 95-97%. The growth rate obtained in pearlspot in the short-term feeding trials in the present study is highly comparable to the growth reported for this fish by Shiranee & Natarajan 2 and Annekutty Joseph et al. 1. The weight gain of pearlspot(table 4) increased with addition of lipid in the diet up to 5%. The diet that had a total lipid content of 8.6%(with 5% supplementation) had given significantly (P<0.05) higher

5 AHAMAD ALI: DIET OF PEARLSPOT (Etroplus Suratensis) 285 Table 4 Results of feeding trials with test feeds 9 15 on pearlspot for 35 days Dietary fat content Test Feeds (9 15) 3.2% 4.3% 6.2% 8.6% 11.8% 13.5% 18.4% Initial average weight (g) (+SD) Final average weight (g)(+sd) Increase in weight (g) (+SD) 16.06± ± ± ± ± ± ± ± ± ± ± ± ± ± b ± b ± b ± a ± b ± b ± b ±1.37 SGR ± ± ± ± ± ± ±0.078 FGR 3.16 b 1.76 a 1.80 a 1.60 a 2.60 b 2.80 b 2.70 b PER 0.96 c 1.73 a 1.69 a 1.94 a 1.21 b 1.09 bc 1.13 bc Survival % ANOVA EMS SE CD (0.05) Weight gain FGR PER Values with same superscript do not differ significantly (P>0.05) among themselves. weight gain (18.24 ± 0.84g) and lowest FGR (1.6). The protein efficiency ratio (PER) also improved with increase in the dietary lipid level and significantly (p<0.05) better PER was recorded (1.94) by the diet with 8.6% of total lipid. Further increase in the lipid supplementation in diet appears to have negative effect on growth, FGR and PER indicating that pearlspot does not seem to utilize lipid energy source for growth at tropical temperature. The survival of the fish fed with different diets was good. Lipid is the highest energy source (8-9 kcal/g) in diet. It is shown to play the role of sparing protein in diet for fish 15. The lipid levels in cichlid fish diets are generally in the range of 7-9%. However, higher lipid levels are recommended for preparing high-energy diets (more than 16 MJ per kg in diets of salmonids) to make the feeds less polluting 16. But in the case of pearlspot higher lipid levels have produced negative effect. The present study revealed that quantitative lipid level in diet is 8-9% for optimum growth for pearlspot, which is in agreement with findings in freshwater carps 8 and marine fish (milkfish, Chanos chanos) and is also within the range of lipid levels found in the diets of different teleost species. In conclusion, the results obtained in this study can be utilized for formulating practical feeds using low cost lipid sources for feeding pearlpsot for its aquaculture. This study also gives base line data on the class of lipid and possible fatty acid needs of pearlspot and suggests investigations on more specific dietary fatty acid requirements of Etroplus suratensis. Acknowledgement The author expresses his sincere thanks to the Director, Central Institute of Brackishwater Aquaculture for providing necessary facilities for carrying out this work. Thanks are due to Mrs. Ch. Sarada, Scientist, CIBA for helping in statistical analysis of the data. References 1 Annekutty Joseph, Sherief P M & Thresiamma James, Effect of different dietary inclusion levels of Azolla pinnata on the growth, FCR and muscle composition of Etroplus suratensis (Bloch), J Aqua Trops, 9 (1994) Shiranee P & Natarajan P, Impact of compunded feed on the growth, muscle composition and organoleptic charateristics of pearlspot (Etroplus suratensis) (Bloch), J Aqua Trops, 10 (1995) Ahamad Ali S, Effect of dietary ingredient composition and protein level on growth and food conversion ratio in pearlspot (Etroplus suratensis) (Bloch), J Aqua Trops (in press). 4 AOAC. Official methods of analysis (Association of Official Analytical Chemists Inc USA, Washington D.C), 1990, pp Snedecor G W & Cochran W G, Statistical methods, 6 th edition (IOWA State University Press, Ames, Iowa), 1973, pp Gopalan G, Ramasastri B V & Balasubramnian S C, in Nutritive value of Indian Foods (National Institute of Nutrition, Indian Council of Medical Research, Hyderabad) 1991, pp. 86.

6 286 INDIAN J. MAR. SCI., VOL. 33, NO. 3, SEPTEMBER Satoh S, Common carp, Cyprinus carpio, in Handbook of nutrient requirements of fish, edited by R.P. Wilson (CRC Press, Inc, Florida, USA) 1991, pp Guillaume J & Kaushik S J, Tropical fish nutrition, Paper presented at the Fish Nutrition Workshop, Singapore SGP, October 25-27, Das K M, MohantyS N & Sarkar S, Optimum dietary protein energy for Labeo rohita fingerlings, in Fish nutrition research in Asia, edited by S.S. De Silva (Asian Fisheries Society, Manila, Philippines) 1991, pp Shiranee P & Natarajan P, Crude palm as a source of carotenoids and tocopherols to enhance reproductive potential in pearlspot (Etroplus suratensis) (Bloch), J Aqua Trops, 9 (1996) Viola S, Arieli Y & Zohar G, Animal protein free feeds for hybrid tilapia (Orechromis niloticus O. auresu) in intensive culture, Aquaculture, 75 (1988) Viola S & Ariel Y, Nutrition studies with tilapia hybrids. (2) The effects of supplements to practical diets for intensive aquaculture, Bamidgeh, 35 (1983) Guillou A, Soucy P, Khalil M & Andambounow L, Effect of dietary vegetable and marine lipid on growth, muscle fatty acid composition and organoleptic quality of flesh of brook charr (Salvelinus fontinalis), Aquaculture, 136 (1995) Fontagne S, Pruszneki T, Corraze G & Bergot P, Effect of coconut and tricaprylinvs. triolin on survival, growth and fatty acid, Aquaculture, 179 (1999) Cho C Y & Kaushik S J, Effects of protein intake on metabolizable and net energy values of fish diets, in Fish feeding and nutrition, edited by C.B. Cowey, A.M. Mackie, J.G. Bell (Academic Press, London), 1985, pp Alsted N D, Studies on the reduction of discharges from fish farms by modification of the diet, in National strategies and aquaculture waste, edited by C.B. Cowey & C.Y. Cho (University of Guelph, Canada), 1991, pp