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0.91±0.01c

1.12±0.04ab

1.09±0.01ab

Values are means ±S.D. Values with the same superscripts within the same row are not significantly different

(P < 0.05).

1See Table 1 for diet abbreviations. 2FCR, food conversion ratio;

3DGR, Daily growth rate; 4SGR, specific growth rate;

5HIS, Hepatosomatic index; 6VSI, viscerosomatic index;

7CF, Condition factor.

Hepatosomatic index (HIS) was significantly higher in fish fed diet with PP, 50PP/50PM and PM groups compared to control group (P < 0.05). No significant differences were observed in HIS among 50FM/50PP and control group (P > 0.05). Viscerosomatic index (VSI) was significantly higher in fish fed diet with plant protein sources (PP) compared to control group (P < 0.05). However no significant differences were observed in VSL among other feeding treatments (P > 0.05). No significant differences were observed in Condition factor (CF) among FM, 50PP/50PM and PM groups. But CF was significantly higher in fish

fed diet with 50FM/50PP and significantly lowers in PP compared to control group (P < 0.05).

Discussion

Results showed that substituting 50% fish meal with gluten-based protein (50 FM/50PP) does not adversely affect the fish growth. This is in accordance with replacing 30 and 35% fish meal with wheat gluten in Atlantic salmon and Atlantic halibut respectively (Storebakken et al. 2000; Helland and Grisdale-helland, 2006) and 50% fish meal with corn gluten in Atlantic salmon (Mente et al. 2003). However, growth indices decreased significantly by substitution of 100% fish meal with plant protein sources (Francesco et al. 2004; Palmegiano et al. 2006; Santigosa et al. 2008), and PBM as sole source of protein in the diet of rainbow trout (Fowler, 1991; Steffens, 1994). It is proposed that inclusion of higher levels of plant ingredients and PBM in salmonids diets has adverse effect on fish performance.

Recent studies on concentrated plant protein inclusion in rainbow trout diet showed that it can potentially replace whole dietary fish meal with either no reduction or just a slight reduction in growth (Kaushik et al. 1995), which is in contrast with our findings. There are several explanations for undesirable effects of higher levels of plant derived ingredients in salmonids diet such as higher carbohydrate content which is not generally well digested by salmonids (Singh and Nose 1967). However, it is not conceivable that carbohydrate could have noticeable effects on fish growth in this study, since all diets had balanced carbohydrate content. We incorporated wheat and corn gluten because of their higher content of protein, lower amounts of fiber and starch and relatively void of any ANFs (Robaina et al. 1997). Moreover, wheat and corn gluten have proved higher digestibility coefficients (99 and 95-96%) in salmonids (Yamamoto and Akiyama, 1997).

Essential amino acids are necessary for optimal growth rate and better fish performance (Halver and Hardy 2002). Another problem arisen from higher plant derived ingredients in aquafeed is their lower protein and

essential amino acids contents compared to fish meal. However, gluten based protein contains high protein levels but it is deficient in some essential amino acids such as lysine and methionine (Regost et al. 1999). The animal by-product meals such as PMB also contain less amounts of methionine, lysine, and isoleucine (Mente et al. 2003). However, it was observed that supplementation of 0.4% lysine and 1.2% methionine alone does not support fish growth indices which is in agreement with findings of Francesco et al. (2004) and Steffens (1994) in rainbow trout, and with results of fowler (1982) on Chinook salmon fry. However, in another study a maximum level of 20% fishmeal replacement by PBM was found to be a practical diet for juvenile fall Chinook salmon (Fowler, 1991).

Conclusion

Based on the results obtained from present study it was concluded that supplementation of 50% fish meal with combination of plant proteins (wheat and corn gluten and soybean meal) and 100% fish meal with combination of plant proteins (50%) and Poultry by-product meal (50%) without significant negative effects on growth indices.

Acknowledgements

This study was supported by Artemia and Aquatic Animals Research Institute and Faculty of Natural Resources of Urmia University, Iran.

References

Appelbaum, S., Birkan, V. and Prilutzly, A. 1996. Use of chicken meal as a substitute for fish meal in the diet of young eels. Archives of Polish Fisheries, 4: 141-145.

Fowler, L.G. 1991. Poultry by product meal as a dietary protein source in fall chinook salmon diets. Aquaculture, 99: 309-321.

Fowler, L.G. 1982. 1981 tests with poultry by-product meal in fall chinook salmon diets. U.S. Fish and Wildlife Service, Abernathy Salmon Cultural Development Transfer Series No. 82- 1.

Francesco, M., Parisi, G., Medale, F., Kaushik, S.J. and Poli, B.M. 2004. Effect of long term feeding with a plant protein mixture based diet on growth and body/fillet quality traits of large rainbow trout (Oncorhynchus mykiss). Aquaculture 263, 413-429.

Francis, G., Makkar, H.P.S. and Becker, K. 2001. Anti-nutritional factors present in plant-derived alternate fish feed ingredients and their effects in fish. Aquaculture 199, 197-227.

Halver, J.E. and Hardy, R.E. 2002. Nutrient flow and retention In Fish Nutrition, 3rd edn, pp. 768-769. Academic Press, Elsevier Science, San Diego, California, USA.

Hasan, M.R. and Das, P.M. 1993. A Preliminary study on the use of poultry offal meal as dietary protein source for the fingerlings of Indian major carp, Laboe rohita (Hamilton). S.J. Kaushik and P. Luquet (Eds.), Fish Nutrition Practise, Institut National de la Recheche Agronomique, Paris: 793-801.

Helland, S.J. and Grisdale-helland, B. 2006. Replacement of fish meal with wheat gluten in diets for Atlantic halibut ( Hippoglos sushippoglossus ): Effect on whole-body amino acid concentrations. Aquaculture 261:1363 - 1370.

Higgs, D.A., Markert, J.R., Macourarie, D.W., Mcbride, J.R., Dosanjh, B.S., Nichols, C. and Hoskins, G. 1979. Development of practical dry diets for coho salmon, Oncorynchus kisutch, using poultry by product meal, feather meal, soybean meal and and rapeseed meal as major protein sources. K. Tiews and J.E. Halver (Eds.), Finfish Nutrition and Fish Feed Technology, Vol. II, Hieennemann Gmbh, Berlin: 191-218.

Mente, E., Deguara, S., Santos, M.B. and Houlihan, D.F. 2003. White muscle free amino acid concentrations following feeding a maize gluten dietary protein in Atlantic salmon (Salmo salar L.). Aquaculture 225, 133-147.

Nengas, L., Alexis, M. and Davies, S.J. 1999. High inclusion levels of poultry meals and related by-product in diets for gilthead seabream (Sparus aurata L.). Aquaculture 179, 13-23.

NRC, 1993. Nutrient Requirements of Fish. National Academy Press, Washington, DC.

Palmegiano, G.B., Dapra, F., Forneris, G., Gai, F., Gasco, L., Guo, K., Peiretti, P.G., Sicuro, B. and Zoccarato, I. 2006. Rice protein concentrate meal as a potential ingredient in practical diets for rainbow trout (Oncorhynchus mykiss). Aquaculture 258:357-367

Regost, C., Arzel, J. and Kaushik, S.J. 1999. Partial or total replacement of fish meal by corn gluten meal in diet for turbot (Psetta maxima). Aquaculture 180:99-117.

Robaina, L., Izquierdo, M.S., Moyano, F.J., Socorro, J., Vergara, J.M., Montero, D. and Fernandez-Palacios, H. 1995. Soybean and lupin seed meals as protein sources in diets for gilthead seabream (Sparus aurata): nutritional and histological implications. Aquaculture 130, 219-233.

Robaina, L., Moyano, F.J., Izquierdo, M.S., Socorro, J., Vergara, J.M. and Montero, D. 1997. Corn gluten meal and meat and bone meals as protein sources in diets for gilthead seabream (Sparus aurata): nutritional and histological implications.

Aquaculture 157, 347-359.

Rollin, X., Mambrini, M., Abboudi, T., Larondelle, Y., Kaushik, S.J., 2003. The optimum dietary indispensable amino acid pattern for growing Atlantic salmon

(Salmo salar) fry. Br. J. Nutr. 90, 865-876.

Sadiku, S.O.E. and Jauncey, K. 1995. Soybean flour-poultry meat meal blend as dietary protein source in practical diets of Oreochromis niloticus and Clarias gariepinus. Asian Fisheries Science, 8: 159-167.

Santigosa, E., Sanchez, J., M6dale, F., Kaushik, S., P6rez-Sinchez, J. and Gallardo, M. A. 2008. Modifications of digestive enzymes in trout (Oncorhynchus mykiss) and sea bream (Sparus aurata) in response to dietary fish meal replacement by plant protein sources. Aquaculture 282, 68-74.

Singh, R.P. and Nose, T. 1967. Digestibility of carbohydrates in young rainbow trout. Bull. Freshwater Fish. Res. Lab 17, 21-25.

Sokal, R.R. and Rohlf, F.J. 1969. Biometry. Freeman, San Francisco, CA, USA.

Steffens, W. 1994. Replacing fish meal with poultry by- product meal in diets for rainbow trout, Oncorhynchus mykiss. Aquaculture, 124: 27-34.

Storebakken, T., Shearer, K.D., Baeverfjord, G., Nielsen, B.G., Asgard, T., Scott, T.M.

and De Laporte, A. 2000. Digestibility of macronutrients, energy and amino acids, absorption of elements and absence of intestinal enteritis in Atlantic salmon, Salmo salar, fed diets with wheat gluten. Aquaculture 184, 115-132.

Yamamoto, T., Ikeda, K., Unuma, T. and Akiyama T. 1997. Apparent availabilities of amino acids and minerals from several protein sources for fingerling rainbow

trout. Fish Science 63, 995-1001.

Total substitution of fish oil by vegetable oils in rainbow trout (Oncorhynchus mykiss) fry diets: Effects on growth performance

Reza Jalili*1, Naser Agh2, Ahmad Imani1, Reza Asgari1, Forouzan Bagherzadeh Lakani1

1 Department of Fisheries, Faculty of Natural Resources, Urmia University, Iran

2 Department of Fisheries, Artemia and Aquatic Animals Research Institute, Urmia University, Iran

* Corresponding author; Tel.: +98 441 3467097, E-mail address: Re.Jalili@gmail.com Abstract

The present study was performed to examine the effect of replacing fish oil with different vegetable oil on growth performance of rainbow trout fry. Five experimental diets with a similar gross composition were formulated with different vegetable oil sources; kilka oil (FO), canola oil (CO), safflower oil (SO) and a mixture of SO (70%) and LO (30%) (SLO) were used as dietary lipid sources. In all experimental diets fish meal was completely defatted. Rainbow trout fry with a mean initial weight of 0.1+0.005 g were fed experimental diets for 60 days. Results showed that no significant differences were detected in growth indices of fish fed FO and those were fed on diet containing CO. However, total replacement of fish oil with SO and SLO resulted in decreased final body weight and SGR. Viscerosomatic index (VSI) was significantly higher in fish fed diet with CO compared to control group (P < 0.05). However no significant differences were observed in VSL among other feeding treatments (P > 0.05). No significant differences were detected in HSI among treatments. CF was significantly higher in fish fed diet with CO and SLO compared to control group (P < 0.05). However, total replacement of fish oil with SO resulted in decreased CF compared to other groups (P < 0.05).

Key words: Vegetable oil, Fish oil, Growth, Rainbow trout, Fry

Fish meal and fish oil are the main ingredients used in aquafeed formulation. The rapid expansion of aquaculture production has been accompanied by a rapid growth of aquafeed production. Total industrial compound aquafeed production has increased over three-fold from 7.6 million tonnes in 1995 to 27.1 million tonnes in 2007 and it is expected to reach 70.9 million tonnes by 2020 (Tacon et al,, 2012). Meanwhile, annual fish oil (FO) production has not increased beyond 1.5 million tonnes per year and the rapidly growing aquaculture sector cannot continue to rely on finite stocks of marine sources (Turchini et al., 2009). Fish oil supplies energy and essential fatty acids (EFAs) to the farmed animal (Stubhang et al., 2007).Vegetable oils such as linseed and canola oil are rich in LNA (18:3n-3) (NRC, 1993). Although they are devoid of HUFA, freshwater species are capable of converting dietary LA to AA and LNA to EPA and DHA (Bell et al.,2001).Numerous studies have shown that vegetable oils can replace a significant portion of fish oil in salmonids diet (Bell et al., 2003). Mean while, some literatures promisingly showed fish oil may be completely replaced with vegetable oils in rainbow trout (Drew et al., 2007). However, regardless of the dietary lipid sources used, EFA deficiency is unlikely because fish meal usually contains 8-10% oil comprising 20 to 35% HUFA (Turchini et al., 2009). Accordingly, one should be more cautious interpreting results from such experiments since that dietary protein source and state would affect the results. This research was to study the probable effects of total fish oil replacement by different vegetable oils on growth and feed utilization indices of rainbow trout.

Materials and methods

Fish husbandry and diet preparation

The rainbow trout (Oncorhynchus mykiss) fry used in this experiment came from a batch of eyed (embryonic) eggs from a commercial fish farm of domestic origin. Fry were reared in our laboratory hatchery from eggs to the beginning of the experiment, according to Rollin et al. (2003). Hundred fish with average weight of 100+5 mg were stocked in 15 tank (8 L)

supplied with freshwater at a flow rate of 1.5 L min-1. Light/dark cycle was 12 L:12 D. The pH (7.3-7.7), temperature (14-15°C) and dissolved oxygen level (7.5-7.8 mgL-1) of each tank were monitored daily.

Five experimental diets with a similar protein (%50+1), lipid (%20+1) and energy (5.48+0.3 kcal/g) content were formulated with different vegetable oil sources; kilka oil (FO), canola oil (CO), safflower oil (SO), and a mixture of SO (70%) and LO (30%) (SLO) were used as dietary lipid sources (Table 1).

Briefly, all dry ingredients were thoroughly mixed in a mixer. Oil was added and thoroughly mixed for 3 min and then moistened by adding cold distilled water until stiff dough yielded. The strands were dried at 50°C for 8 h using an oven, manually crumbled into appropriate size and sieved. Pellets were stored at 4°C during the experiment. Fish were fed three times per day at 7-9 % body weight for 8 weeks.

Growth parameters and feed utilization indices

On the first and the last day of the experiment fish were weighed (W+0.01 g) and total lengths were measured (TL+0.1 cm). Following parameters were calculated:

Specific growth rate (SGR, %d-1)=100x[(lnWf-lnWi)xT-1]; Condition factor (CF)=100x(WxTL-3); days reared. Where: Wf and Wi are the final and initial body weights (g), T—time of rearing (days), FB and IB are the final and initial absolute weights (g).

Collection of samples

At the start of the experiment and at the end of the growth period, 12 fish/tank were sampled for measurements (weight and total length). Nine fish per tank were removed to weigh the liver and digestive tract for measurement of hepatosomatic index (HSI) and viscerosomatic index (VSI).

Proximate composition of diets

Feeds was determined by drying in oven (Iran khodsaz Co, Iran) at 105°C for 25 h to a constant weight; ash was determined by incineration in a muffle furnace (Iran khodsaz Co, Iran) at 600 C for 6 h; crude protein was determined by the Kjeldahl method (N x 6.25) using an

automatic Kjeldahl system (Behrotest WD 40, Germany); Crude lipid content determination was conducted by ether extraction. Gross energy content of the diets was calculated on the basis of 5.64, 9.43, and 4.11 (kcal/g diet) of protein, fat, and carbohydrate, respectively (NRC 1993).

Statistical analysis

The results were analysed using analysis of variance, one way ANOVA, for which the homogeneity of variances and the normal distribution were tested according to the Levene and Shapiro_Wilk tests, and comparison among the means was made using Duncan's multiple range test (DMRT) (Sokal & Rohlf 1969). All statistical analyses were conducted using SPSS (version16) and tested at P < 0.05.

Table 1 Ingredient and proximate composition of experimental diets

Ingredients (g kg-1 diet)

 

Dietarytreatments

 

 

FO

CO

SO

SLO1

Defatted Fish meal

678

678

678

678

Fish oil

199

-

-

190

Canola oil

-

199

-

-

Safflower oil

-

-

199

139.3

Linseed oil

-

-

-

59.7

Blood meal

20

20

20

20

Wheat meal

30

30

30

30

Wheat starch

24

24

24

24

Vitamin premix2

15

15

15

15

Mineral premix3

10

10

10

10

L-methionine

12

12

12

12

L-lysine

2

2

2

2

Di-calcium phosphate

5

5

5

5

Calcium carbonate

5

5

5

5

1 SLO: linseed oil (30%) and safflower oil (70%). 2Vitamin permix: (mg or IU/kg of diet) Vitamin A (as

acetate) 1600000 IU; vitamin D3, 400000 IU; choline chloride.12000; niacin, 4000; riboflavin, 8000;

pyridoxine, 4000; folic acid, 2000; vitamin B12, 8000; biotin, 1; inositol, 20000; vitamin C, 60000; vitamin H2, 2.4; vitamin B2, 8000; vitamin K3, 2000; vitamin E,40000. 3Mineral mixture (g/kg): zinc, 12.5 g; iron, 26 g; manganese, 15.8 g; copper, 4.2 g; cobalt, 0.48 g; selenium, 2 g; iodine, 1 g.

Results and Discussions

As depicted in table 2, no significant differences were detected in growth indices of fish fed FO and those were fed on diet containing CO. However, total replacement of fish oil with SO and SLO resulted in decreased final body weight and SGR. Viscerosomatic index (VSI) was significantly higher in fish fed diet with CO compared to control group (P < 0.05). However no significant differences were observed in VSL among other feeding treatments (P > 0.05). No significant differences were detected in HSI among treatments. CF was significantly higher in fish fed diet with CO and SLO compared to control group (P < 0.05). However, total replacement of fish oil with SO resulted in decreased CF compared to other groups.

Table 2 Growth and feed utilization indices of different experimental groups

Performance parameters

 

Dietary treatments1

 

 

FO

CO

SO

SLO

Final body weight (g)

1.43±0.09a

1.46±0.12a

0.94±0.02c

1.22±0.07b

Length (cm)

5.07±0.1a

4.93±0.1a

4.93±0.05c

4.64±0.1b

SGR4

1.92±0.04a

1.94±0.05a

1.62±0.01b

1.81±0.04b

HIS5

3.64±0.7a

3.2±0.8a

2.84±0.25a

3.34±0.23a

VSI6

16.5±1.7b

20.2±0.6a

16.8±1.3b

18.3±1.2ab

CF7

1.08±0.01b

1.19±0.01a

1.05±0.03c

1.19±0.01a

Values are means ±S.D. Values with the same superscripts within the same row are not significantly different (P < 0.05). 1See Table 1 for diet abbreviations.2FCR, food conversion ratio; 3DGR, Daily growth rate; 4SGR, specific growth rate; 5HIS, Hepatosomatic index; 6VSI, viscerosomatic index; 7CF, Condition factor.

The present study showed that it is possible to totally replace fish oil by CO without any apparent undesirable effects on fish growth performance. While it was stated that LO is a promising candidate for salmonids (Bendiksen and Jobling, 2004), this study did not support the previous results. This contrasting results might be due to the fact that within each plant species, many variants are available that differ in their fatty acid profiles and consequently their nutritional value. Canola oil, another popular oilseed, has yielded promising results. In conclusion, it

seems that CO are promising sources of dietary lipid for rainbow trout fry; however, thorough conclusion needs precise and complete examinations. This study is still ongoing and further biochemical and histological assessments are being undertaken.

References

Bell, J.G., McEvoy, J., Tocher, D.R., McGhee, F., Campbell, P.J.,Sargent, J.R., 2001.Replacement of fish oil with rape seedoil in diets of Atlantic salmon (Salmosalar) affects tissuelipid compositions and hepatocyte fatty acid metabolismJournal of Nutrition 131: 1535-1543.

Bell, J.G., Tocher, D.R:, Henderson, R.J., Dick, J.R., Crampton, V.O., 2003b. Altered fatty acid compositions in Atlantic salmon (Salmosalar) fed diets containing linseed and rapeseed oils can be partially restored by a subsequent fish oil finishing diet. Journal of Nutrition 133: 2793-2801.

Bendiksen, E., Jobling, M., 2004.Effects of temperature and feed composition on essential fatty acid (n-3 and n-6) retention in Atlantic salmon (Salmosalar L.) parr. Fish Physiology and Biochemistry 29: 133-140.

Drew M.D., Ogunkoya A.E., Janz D.M. & Van Kessel A.G. (2007) Dietary influence of replacing fish meal and oil with canola protein concentrate and vegetable oils on growth performance, fatty acid composition and organochlorine residues in rainbow trout (Oncorhynchusmykiss). Aquaculture 267, 260-268.

NRC (1993) Nutrient Requirements of Fish.National Academy Press, Washington, DC.

Stubhang, I., 0. Lie and B.E. Torstensen. (2007). Fatty acid productive value and □­oxidation capacity in Atlantic salmon tissues (Salmo salar L.) fed on different lipid sources along the whole growth period. Aquaculture Nutrition 13: 145 - 155.

Tacon, A. G.J., Hsan, M.R., Allan, G., El-Sayed, A.-F.M., Jackson, A., Kaushik, S.J.,

Ng, W-K., Suresh, V., Viana, M.T., 2012. Aquaculture feeds: addressing the long-term sustainability of the sector. In FAO/NACA.Farming the Waters for People and Food. R.P. Subasinghe, J.R. Arthur, D.M. Bartley, S.S. De Silva, M. Halwart, N. Hishamunda, C.V. Mohan & P. Sorgeloos, (Eds.) Proceedings of the Global Conference on Aquaculture 2010, Phuket, Thailand. 22-25 September 2010. FAO, Rome and NACA, Bangkok. 896 pp.

Effects of total fish oil replacement with plant lipid sources on growth performance, feed utilization indices and fillet gross composition of rainbow trout

(Oncorhynchusmykiss)

Reza Jalilia, Naser Aghb, Ahmad Imania*

aDepartment of Fisheries, Faculty of Natural Resources, Urmia University, Iran. bDepartment of Fisheries, Artemia and Aquatic Animals Research Institute, Urmia University, Iran

* Tel.: +98 441 3467097, E-mail address: Ahmad_im2003@yahoo.ca Abstract

The present study was performed to examine the effect of replacing fish oil with different vegetable oil on growth performance, feed utilization indices and fillet gross composition of rainbow trout of rainbow trout. Five experimental diets with a similar gross composition were formulated with different vegetable oil sources; kilka oil (FO), canola oil (CO), safflower oil (SO), linseed oil (LO) and a mixture of CO (40%), SO (30%) and LO (30%) were used as dietary lipid sources. In all experimental diets fish meal was completely defatted. Rainbow trout with a mean initial weight of 15±0.4 g were fed experimental diets for 60 days. Results showed that no significant differences were detected in growth indices of fish fed FO and those were fed on diet containing CO and CSLO. But fish fed SO and LO resulted in decreased WG, SGR and DGR. HSI was significantly lower in CO group, while it was significantly higher in CSLO group in comparison to control. CO and LO had significantly lower VSI than other treatments (P< 0.05). CF was significantly higher in fish fed diet containing 100% vegetable oil (CO, SO, LO and CSLO), comparing to FO (P<0.05). No significant differences were detected in protein PPV among treatments. PER decreased significantly in SO and LO groups compared to those fed fish oil. However, PER from CO and CSLO groups did not show any significant differences compared FO (P< 0.05). Replacement of fish oil

with vegetable oils (CO, SO, LO and CSLO groups) resulted in significantly lower LPV compared to those fed fish oil (P< 0.05). LER in CO, SO and LO was significantly lower compared FO group (P< 0.05). Replacement of fish oil with vegetable oils (CO, SO, LO and CSLO groups) resulted in significantly higher muscle protein and ash content. However, plant oil inclusion led to lower fillet lipid content in comparison to FO (P< 0.05).

Key words: Plant oil, Fish oil, Growth, Rainbow trout.

Introduction

Fish meal and fish oil are the main ingredients used in aquafeed formulation. The rapid expansion of aquaculture production has been accompanied by a rapid growth of aquafeed production. Total industrial compound aquafeed production has increased over three-fold from 7.6 million tonnes in 1995 to 27.1 million tonnes in 2007 and it is expected to reach 70.9 million tonnes by 2020 (Tacon et al,, 2012). Meanwhile, annual fish oil (FO) production has not increased beyond 1.5 million tonnes per year and the rapidly growing aquaculture sector can not continue to rely on finite stocks of marine sources (Turchini et al., 2009). Fish oil supplies energy and essential fatty acids (EFAs) to the farmed animal (Stubhang et al., 2007).Vegetable oils such as linseed and canola oil are rich in LNA (18:3n-3) (NRC, 1993). Althoughthey are devoid of HUFA, freshwater species are capable of converting dietary LA to AAand LNA to EPA and DHA (Bell et al.,2001).Numerous studies have shown that vegetable oils can replace a significant portion of fish oil in salmonids diet (Bell et al., 2003). Mean while, some literatures promisingly showed fish oil may be completely replaced with vegetable oils in rainbow trout (Drew et al., 2007). However, regardless of the dietary lipid sources used, EFA deficiency is unlikely becausefish meal usually contains 8-10% oil comprising 20 to 35% HUFA (Turchini et al., 2009). Accordingly, one should be more cautious interpreting results

from such experiments since that dietary protein source and state would affect the results. This research was to study the probable effects of total fish oil replacement by different vegetable oils on growth and feed utilization indices of rainbow trout.

Materials and methods

After 2 weeks of acclimation, 40 fish with an average weight of 15±0.2 g were stocked in each 15 tanks (300 L) with a flow rate of 7.5 L min-1 and light/dark cycle of12 L:12 D. Five experimental diets with a similar gross composition were formulated with different vegetable oil sources (Table 1); kilka oil (FO), canola oil (CO), safflower oil (SO),

linseed oil (LO)and a mixture of CO (40%), SO (30%) and LO

(30%)were used as dietary lipid sources. In all experimental diets fish meal was completely defatted (Miller et al., 2007).

Growth and feed utilization indices

On the first and the last days of the experiment, fish were weighed to the nearest 0.01 g and total lengths were also measured to the nearest 0.1 cm. Accordingly, following parameters were calculated: Specific growth rate (SGR, %d-1), Daily growth rate (DGR, g d-1),Weight gain (WG), Condition factor, Feed conversion ratio (FCR), Feed efficiency ratio (FER), Protein efficiency ratio (PER), Protein production value (PPV), Lipid efficiency ratio (LER), Lipid production value (LPV), Hepatosomatic index (HIS) and Viscerosomatic index (VSI) (Lundebye

et al., 2010).

Statistical procedure

The data were analyzed using one way ANOVA, for which the homogeneity of variances and the normal distribution of data set were qualified by Levene's and Shapiro-Wilks tests. Duncan's multiple range test (DMRT) was used for post hoc analyses at p<0.05 (Sokal&Rohlf1969). All statistical analyses were conducted using SPSS (version16).

Table 1 Ingredient and proximate composition of experimental diets

Ingredients (g kg-1 diet)

 

 

Dietary treatments

 

 

FO

CO

SO

LO

CSLO

Defatted Fish meal

540

540

540

540

540

Soybean meal

100

100

100

100

100

Fish oil

143

-

-

-

-

Canola oil

-

143

-

-

-

Safflower oil

-

-

143

-

-

Linseed oil

-

-

-

143

-

Vegetable oil1

-

-

-

-

143

Blood meal

40

40

40

40

40

Wheat meal

70

70

70

70

70

Wheat starch

60

60

60

60

60

Vitamin premix2

15

15

15

15

15

Mineral premix3

10

10

10

10

10

L-methionine

10

10

10

10

10

L-lysine

2

2

2

2

2

Di-calcium phosphate

5

5

5

5

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