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L-methionine

12

12

Di-calcium phosphate

5

5

Calcium carbonate

5

5

Proximate composition (% dry matter)

Crude protein

45.3

44.5

Crude lipid

19.9

19.8

Gross energy (kcal/g)4

5.04

5.03

Reproductive performance and eggs quality measurements

Before fertilizing; total Fecundity (TF) were weigh in, then eggs (without ovarian fluid) from all females were weighted and sampled (20-30 g/female). 1-2 g of each female eggs were separated and used for early eggs wet weight (before water-hardening), fecundity rate(Absolute Fecundity{AF= Total Fecundity weight/ eggs wet weight means} & Relative Fecundity{RF= Absolute Fecundity/Fish Weight}) measurement. After fertilizing; Egg diameter(ED), final Eggs wet weight(FEWW), water-hardening rate of eggs (WHR(%)= [ln final weight - ln initial Weight / ln initial Weight] x 100), Fertilization rate (FR=[Fertilized egg/total egg] x 100) and hatching rate (HR%= [number of hatched larvae/ total incubated eggs] x 100) were measured. Fertilization rate was checked by clearing eggs (One hundred egg from each brood, randomly) in acetic acid (3%) at 24 h post-fertilization. The diameter of eggs was determind by a caliper.

Statistical analysis

All assays were conducted in 2 groups and the mean ± S.D was calculated for groups. Data were analysed using T test analysis.

Result and Discussion

Reproductive performance is deeply affected by the nutritional status of fish, which is known to condition several reproductive traits, such as age at maturity, fecundity, egg size, chemical composition of eggs and also embryonic development (Carillo et al. 2000). In freshwater fish, embryonic development depends on the energetic reserves of the yolk sac. This is particularly true for Salmonids, as their embryonic structures are highly developed and their trophic function lasts for many days after hatching. Previous research demonstrated that changes in yolk composition, through diet and feeding levels, could also affect fry survival (Knox et al. 1988)

Reproductive performance of rainbow trout broodstocks fed the experimental diets are shown in table 3. No significant differences were

detected in growth of fish fed control diet (FO) and vegetable group (VO). Replacement of fish oil with blend vegetable oils (canola: linseed: safflower oil, 40:30:30, respectively) resulted in decreased total fecundity compared to control group (P<0.05). However, No significant differences were observed in absolute fecundity and relative fecundity among feeding treatments (P>0.05). However, eggs weight, eggs diameter and fertilization rate in group fed with vegetable oil (VO) did not show any significant differences compared to the control group (FO).

Watanabe et al. (1984) observed that lipid sources in broodstock diets affect egg quality, their hatching rate, also demonstrating that a dietary fatty acid deficiency could cause a decrease in gamete numbers and a high mortality of embryos, which is in agreement with our results. Results showed replacement of fish oil with blend vegetable resulted in significantly decreased hatching rate and increase larvae mortality and deformed larvae rate compared to fish fed fish oil diet (P < 0.05).

References

Bromage N. and Roberts R.J. 1995. Broodstock management and seed quality-general considerations. In: Bromage and Roberts (eds), Broodstock Management and Egg and Larval Quality. Blackwell Science, pp. 424.

Carillo M., Zanuy S., Oyen F., Cerda J., Navas J.M. and Ramos J. 2000. Some criteria of the quality of the progeny as indicators of physiological broodstock fitness. In: Proceeding of the seminar of the CIHEAM Newtwork onTEchnology of Aquaculture in the Mediterranean (TECAM), jointly orga- nized by CIHEAM and FAO, Zaragoza (Spain), 24-28 May 1999. pp. 1-9.

Cho C.Y. and Kaushik S.J. 1990. Nutritional energetics in fish: energy and protein utilization in rainbow trout. World Review of Nutrition and Dietetics 61: 132­172.

Da Silva S.S. and Anderson T.A. 1995. Broodstock Nutrition. Fish Nutrition in Aquaculture. Chapman & Hall, London, pp. 319.

Knox D., Bromage N.R., Cowey C.B. and Springate R.C. 1988. The effect of broodstock ration size on the composition of rainbow trout egg (Salmo gairdneri). Aquaculture 69: 93-104.

Pickova J., Kiessling A., Petterson A. and Dutta P.C. 1999. Fatty acid and carotenoid composition of eggs from two nonanadromous Atlantic salmon stocks of cultured and wild origin. Fish Physiology and Biochemistry 21: 147-156.

Watanabe T., Takeuchi T., Saito M. and Nishimura K. 1984. Effect of low protein-high calory or essen- tial fatty acid deficiency diet on reproduction of rainbow trout. Bull. Japan. Soc. Sci. Fish. 50: 1207-1215.

Replacement of fish meal/oil with plant sources in diet of Beluga sturgeon (Huso huso) Affects on growth parameters and feed utilization

Naser Agh1*, Reza Jalili2, Masoud Bahram Beigi2

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

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

* Corresponding author. Tel.: +98 441 3467097. E-mail address: Agh1960@ gmail.com

Abstract

The present study was performed to examine the effect of replacing fish meal and fish oil with plant sources on growth performance and feed utilization of beluga sturgeon. beluga sturgeon with a mean initial weight of 133±5 g were fed 6 different experimental diets for 60 days. The control diet contained only fish meal and fish oil as the primary sources of protein and lipid, while the 6 remaining diets either contained fish oil or the canola:linseed:sanflower:safflower oil blend (30:30:30:10, respectively) as the primary lipid source and 40, 60,80 and 100 percent replacement of fish meal with plant protein sources. Results showed 80% fish meal and fish oil replacement with plant sources hadn't significant effects on growth indices and feed utilization. But replacement of fish meal with 100% plant protein in combination with 80% vegetable oils resulted in decreased WG, and SGR and increased FCR compared to other groups (P < 0.05). However, growth parameter in group fed with 80% vegetable oil did not show any significant differences compared to the control group (P > 0.05).

Key words: Plant protein, Plant oil, Growth, Beluga sturgeon

In the recent years, the intensive culture of certain sturgeon species has been advanced as an option to other more traditional fish species such as trout and carp. The Beluga sturgeon (Huso huso) is an increasingly prominent aquaculture species in Russia, Eastern Europe, Turkey, Japan and Iran because of the decreasing natural sources for its caviar and meat. This fish is a commercially important fish and is usually processed into frozen fillets (Dragoev et al. 1998).

Fish meal and fish oil are the main ingredients used in formulation of aquafeed. Due to the expansion of aquaculture activities, marine fisheries will not be able to meet the of aquaculture industry for fish meal and fish oil in not too distant future. The global aquaculture demand for fish meal per year was estimated 2.09 million tons (in 1999), and predicted to reach to nearly 4.6 and 10.4 million tons by 2015 and 2030 respectively (New and Wijkstrom 2002). On the other hand the annual fish oil (FO) production has not increased beyond 1.5 million tons per annum and the rapidly growing aquaculture industry cannot continue to rely on finite stocks of marine pelagic fish as a supply of fish oil (Turchini et al. 2009).

Reviews on alternative protein sources have been advertised by Tacon and Jackson (1998) and Kaushik et al. (1995) Among plant protein sources, some studies report that partial replacement of dietary fish meal with corn gluten meal (12 to 26% of the diet) has lead to sufficient results of growth rates and feed employment in diets for the Oncorhynchus mykiss (Robaina et al. 1995). Alliot et al. (1979) found that replacement of fish meal by corn gluten meal at levels up to 20% did not affect growth or feed efficiency ratios in sea bass (Dicentrurchus labrux) juveniles. The present study was performed to examine the effects of 80% replacement of fish oil with vegetable oil (30:30:30:10 mixture of canola, sunflower, linseed and safflower oil) and partial replacement of fish meal with different dietary levels of plant protein on growth performance and feed utilization of Beluga sturgeon.

Fish husbandry and diet preparation

Twenty fish with average weight of 133±5 g were stocked in 18 polyethylene tanks (300 L) supplied with freshwater at a flow rate of 7.5 L min-1. Light/dark cycle was 12 L:12 D. Water quality parameters were monitored daily for each tank and pH, temperature and dissolved oxygen were maintained at 7.3-7.7, 14-15°C and 6.8-7.5 mg L-1, respectively.

Six experimental diets with similar protein, lipid, energy, calcium and phosphor content were formulated to contain graded levels of plant protein and blend vegetable oil sources to replace fish meal and fish oil (Table 1). Kilka (Clupeonella sp.) meal and oil (Kilkapodre-sahar, Co, Iran) was the primary sources of fish meal and oil in the control and experimental diets and the experimental vegetable oil source was a mixture of canola:linseed:sunflower:safflower oil (30:30:30:10). The experimental plant protein source were wheat gluten, corn gluten and soybean meal.

Briefly, all dry ingredients were thoroughly mixed in a mixer. Oil was added and thoroughly mixed for 5 min and then moistened by adding cold distilled water until stiff dough yielded. The wet dough was grinded and converted to strands (4 mm in diameter) using a meat grinder. The strands were dried at 50°C for 8 h using an oven. Afterwards, they were manually crumbled into appropriate size and sieved. Pellets were stored at 4°C during the experiment. Fish were fed three times per day at 1-2% body weight for 8 weeks.

Table 1. Percentages of fish meal and fish oil replacement.

Dietary Treatments

Protein source Fish meal        Plant sources1

Fish oil

Oil source Vegetable oil 2

100FM/FO

100%

-

100%

-

100FM/VO

100%

-

20%

100%

60FM/80VO

60%

40%

20%

100%

40FM/80VO

40%

60%

20%

100%

20FM/80VO

20%

80%

20%

100%

0FM/80VO

-

100%

20%

100%

1plant protein source included: wheat gluten-based, corn gluten and soybean meal. 2vegetable oil: was formulated using canola oil (30%), linseed oil (30%), sunflower (30%) and safflower oil (10%).

Specific growth rate (SGR, %d"1)=100x[(lnWf-lnWi)xT"1]; Daily growth rate (DGR, g d-1)=(Wf-Wi)xT-1; Condition factor (CF)=100x(WxTL-3);    days    reared;    Feed    conversion ratio

(FCR)=TFIx(FB-IB)-1.

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), TFI—total feed intake (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.

Growth indices are shown in table 2. No significant differences were detected in growth of fish fed control diet (100FM/FO) and those fed on diet containing 40, 60 and 80% plant meal + 80% vegetable oil

(60FM/80VO, 40FM/80VO and 20FM/80VO). But replacement of fish

meal with 100% plant protein in combination with 80% vegetable oils (0FM/80VO) resulted in decreased final body weight and WG and increased FCR compared to other groups (P < 0.05).

However, growth parameter in group fed with 80% vegetable oil (100FM/VO) did not show any significant differences compared to the control group (100FM/FO). No significant differences were observed in hepatosomatic index (HIS) among feeding treatments.

However replacement of fish meal with 100% plant protein in combination with 80% vegetable oils (0FM/80VO) resulted in increased visceralsomatic index (VSI) compared to other groups (P < 0.05).

Table 2 Growth indices of beluga sturgeon fed experimental diets for 60 days (n=9 fish/tank).

Performance parameters

 

 

Dietary treatment 1

 

 

 

100FM/FO

100FM/VO

60FM/80VO

40FM/80VO

20FM/80VO

0FM/80VO

Initial body weight (g)

133.2±5a

136.6±4a

136.8±6a

131.8±6a

134.4±4a

134.5±7a

Final body weight (g)

256.1±10a

275±15a

266.2±14a

256.7±10a

253±17a

225.7±11b

Weight Gain (g/fish)

122.8±7ab

138.2±7a

129.4±8ab

124.9±9 ab

118.5±10 b

91.2±8c

Feed intake (g/fish)

127.2±7ab

139.7±10a

138.1±10ab

131.1±9ab

119.7±9bc

104.6±10c

FCR2

1.08±0.08 a

1.04±0.08a

1.1±0.09ab

1.08±0.09a

1.04±0.07a

1.25±0.1b

SGR3

1.32±0.06ab

1.38±0.02ab

1.31±0.12ab

1.33±0.16ab

1.29±0.08ab

1.13±0.11b

HIS4

2.32±0.25a

2.3±0.43a

2.25±0.26a

2.31±0.44a

2.28±0.17a

2.42±0.35a

VSI5

5.1±0.3b

5.16±0.5b

5.38±0.4ab

5.39±0.42ab

5.32±0.39ab

6±0.43a

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;

3SGR, specific growth rate; 4HIS, Hepatosomatic index;

5VSI, viscerosomatic index.

In recent years, a significant numbers of researches have been directed on the substitution of fish meal with plant protein source. The suitability of this substitution in terms of growth performance has resulted to be generously variable among fish species and experimental situation. Thus, specific experiments have to be performed for each species.

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; Barrows, Gaylord, Stone & Smith 2007), which is in agreement with our results. Results showed that 80% substituting fish meal and fish oil with plant ingredients did not adversely affect fish growth. However this is in accordance with replacing 100% fish meal with corn gluten and Sesame oil cake in Juvenile Beluga (Huso huso) (Jahanbakhshi et al. 2012).

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 (Pfeffer et al. 1995).

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 that many plant meals contain lower protein and essential amino acids compared to fish meal. 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). As lysine and methionine were supplemented to the plant based experimental diets in present study, any amino acids deficiency as growth inhibitor is overruled.

In the present study, a mixture of linseed, canola, sunflower and safflower oil were used to replace fish oil. These oils were chosen because they are rich in n-3 fatty acid, alpha linolenic acid in linseed and canola oil (53% and 12% respectively; NRC 1993), and n-6 fatty acid, 18:2n-6 in safflower oil and sunflower oil. However, they are devoid of

EPA (20:5n-3) and DHA (22:6n-3). Replacement of fish oil with vegetable oil at all levels of plant protein inclusion had no significant effect on Juvenile Beluga (Huso huso) on growth, feed utilization and muscle proximate composition (Hosseini et al. 2010). This result is in agreement with our results.

With reference to the main aims of this study and the results obtained, we may conclude that dietary 80% fish meal and fish oil in beluga sturgoen diet could be replaced with plant sources without significant negative effects on growth indices and feed efficiency.

Acknowledgements

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

References

Alliot, E., A. Pastoreaud, J. Pelaez and R. Metailler. (1979) Partial substitution of fish meal with corn gluten meal products in diets for sea bass (Dicentrurchus labrax),

pp: 229-238.

Barrows F.T., Gaylord T.G., Stone D.A.J. and Smith C.E. (2007) Effect of protein

source and nutrient density on growth efficiency, histology and plasma amino acid concentration of rainbow trout (Oncorhynchus mykiss Walbaum). Aquaculture Research 38, 1747-1758.

Dragoev, S.G., D.D. Kiosev, S.A. Danchev, N.I. Ioncheva and N.S. Genov. (1998) Study on the oxidative processes in frozen fish. Bulgarian Journal of Agricultural Science, 4: 55-65.

Jahanbakhshi, A., Imanpuor, M., Taghizadeh, V and Shabani, A. (2012) Effects of Replacing Fish Meal with Plant Protein (Sesame Oil Cake and Corn Gluten) on Growth Performance, Survival and Carcass Quality of Juvenile Beluga (Huso huso). World Journal of Fish and Marine Sciences 4 (4): 422-425.

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

Hosseini1, S V., Abedian Kenari, A., Regenstein, J M., Rezaei, M., Nazari, R M and Moghaddasi, M. (2010). Effects of Alternative Dietary Lipid Sources on Growth Performance and Fatty Acid Composition of Beluga Sturgeon, Huso huso, Juveniles. JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Vol. 41, No. 4.

Kaushik S.J., Cravedi J.P., Lalles J.P., Sumpter J., Fauconneau B. & Laroche M. (1995) Partial or total replacement of fish meal by soybean protein on growth, protein utilization, potential estrogenic or antigenic effects, cholesterolemia and flesh quality in rainbow trout (Oncorhynchus mykiss). Aquaculture 133, 257-274.

New M.B. & Wijkstrom U.N. (2002) Use of Fishmeal and Fishoil in Aquafeeds: Further Thoughts on the Fishmeal Trap. FAO Fish Circular No.975. FAO, Rome, Italy.

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

Pfeffer E., Kinzinger S. & Rodenhutscord M. (1995) Influence of the proportion of poultry slaughter by-products and of untreated or hydrothermically treated legume seeds in diets for rainbow trout, Oncorhynchus mykiss Walbaum , on apparent digestibilities of their energy and organic components. Aquaculture Nutrition 1, 111-117.

Regost C., Arzel J. & 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. & 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. & 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.

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

Tacon, A.G.J. and A.J. Jackson, 1985. Utilization of conventional and unconventional protein sources in practical fish feed. Nutrition and Feeding in Fish, 1: 18-145.

Turchini G.M., Torstensen B.E. and Ng W.K. (2009). Fish oil replacement in finfish nutrition. Reviews in Aquaculture 1, 10-57.

Total replacement of fish meal and large portion of fish oil by vegetable oils does not affect growth performance and feed utilization in rainbow trout

(Oncorhynchus mykiss)

Naser Agh1*, Reza Jalili2, Ahmad Imani2

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

2 Department of Fisheries, Faculty of Natural Resources, Urmia University, Iran * Corresponding author.   Tel.: +98 441 3467097.

E-mail address: Agh1960@gmail.com

Abstract

The present study was performed to examine the effect of replacing fish meal and fish oil with plant sources on growth performance and feed utilization of rainbow trout. Rainbow trout with a mean initial weight of 65±2 g were fed 6 different experimental diets for 60 days. The control diet contained only fish meal and fish oil as the primary sources of protein and lipid, while the 6 remaining diets either contained fish oil or the canola:linseed:sanflower:safflower oil blend (30:30:30:10, respectively) as the primary lipid source and 40, 60, 80 and 100 percent replacement of fish meal with plant protein sources. Results showed 100% fish meal replacement with plant protein and 80% replacement of fish oil hadn't significant effects on growth indices and feed utilization. But replacement of fish meal with 60% plant protein in combination with 80% vegetable oils resulted in increased WG, and SGR and decreased FCR compared to other groups (P < 0.05). However, growth parameter in group fed with 80% vegetable oil did not show any significant differences compared to the control group (P > 0.05). Key words: Plant protein, Plant oil, Growth, Rainbow trout

Fish meal and fish oil are the main ingredients used in formulation of aquafeed. Due to the expansion of aquaculture activities, marine fisheries will not be able to meet the of aquaculture industry for fish meal and fish oil in not too distant future. Numerous studies have shown that vegetable oils can replace significant part of fish oil in salmonids diets (Torstensen et al. 2005). Meanwhile some literatures promisingly showed that fish oil may be completely replaced with vegetable oils without compromising growth, feed efficiency or reproduction in rainbow trout (Drew et al. 2007). Many plant protein sources can be used to partially or almost totally replace dietary fish meal (Kaushik et al. 1995; Robaina et al. 1995), provided that the essential amino acid requirements of the fish species are met, the palatability of the diet is improved and the levels of anti-nutritional factors (ANFs) are reduced (Francis et al. 2001). Plant-based diets generally do not meet essential amino acids requirements of fish. Multiple research groups have noted that supplementation with amino acids improves growth performance of trout (Yamamoto et al. 2005). The present study was performed to examine the effects of 80% replacement of fish oil with vegetable oil (30:30:30:10 mixture of canola, sunflower, linseed and safflower oil) and partial replacement of fish meal with different dietary levels of plant protein on growth performance and feed utilization of rainbow trout.

Materials and methods

Fish husbandry and diet preparation

Fish were purchased from a local trout farm and acclimated for 2 weeks during which they were fed commercial diet. Thirty fish with average weight of 65±2 g were stocked in 18 polyethylene tanks (300 L) supplied with freshwater at a flow rate of 7.5 L min-1. Light/dark cycle was 12 L:12 D. Water quality parameters were monitored daily for each tank and pH, temperature and dissolved oxygen were maintained at 7.3­7.7, 14-15°C and 6.8-7.5 mg L-1, respectively.

Six experimental diets with similar protein, lipid, energy, calsium and

phosphor content were formulated to contain graded levels of plant protein and blend vegetable oil sources to replace fish meal and fish oil (Table 1). Kilka (Clupeonella sp.) meal and oil (Kilkapodre-sahar, Co, Iran) was the primary sources of fish meal and oil in the control and experimental diets and the experimental vegetable oil source was a mixture of canola:linseed:sunflower:safflower oil (30:30:30:10). The experimental plant protein source were wheat gluten, corn gluten and soybean meal.

Briefly, all dry ingredients were thoroughly mixed in a mixer. Oil was added and thoroughly mixed for 5 min and then moistened by adding cold distilled water until stiff dough yielded. The wet dough was grinded and converted to strands (4 mm in diameter) using a meat grinder. The strands were dried at 50°C for 8 h using an oven. Afterwards, they were manually crumbled into appropriate size and sieved. Pellets were stored at 4°C during the experiment. Fish were fed three times per day at 2% body weight for 8 weeks.

Table 1. Percentages of fish meal and fish oil replacement.

Dietary Treatments

Protein source Fish meal     Plant sources 1

Fish oil

Oil source

Vegetable oil 2

100FM/FO

100%

-

100%

-

100FM/VO

100%

-

20%

100%

60FM/80VO

60%

40%

20%

100%

40FM/80VO

40%

60%

20%

100%

20FM/80VO

20%

80%

20%

100%

0FM/80VO

-

100%

20%

100%

1 plant protein source included: wheat gluten-based, corn gluten and soybean meal.

2 vegetable oil: was formulated using canola oil (30%), linseed oil (30%), sunflower (30%) and safflower oil (10%).

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]; Daily growth rate (DGR, g d-1)=(Wf-Wi)xT-1; Condition factor (CF)=100x(WxTL-3); days reared; Feed conversion ratio (FCR)=TFIx(FB-IB)-1.

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), TFI—total feed intake (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.

Growth indices are shown in table 2. No significant differences were detected in growth of fish fed control diet (100FM/FO) and those fed on diet containing 40, 80 and 100% plant meal + 80% vegetable oil

(60FM/80VO, 20FM/80VO and 0FM/80VO). But replacement of fish

meal with 60% plant protein in combination with 80% vegetable oils

(40FM/80VO) resulted in increased final body weight, WG, and SGR

and decreased FCR compared to other groups (P < 0.05).

However, growth parameter in group fed with 80% vegetable oil (100FM/VO) did not show any significant differences compared to the control group (100FM/FO). No significant differences were observed in hepatosomatic index (HIS), visceralsomatic index (VSI) Condition factor (CF) among feeding treatments.

Table 2 Growth indices of rainbow trout fed experimental diets for 60 days (n=9 fish/tank)._

Dietary treatment 1

Performance parameters -

 

100FM/FO

100FM/VO

60FM/80VO

40FM/80VO

20FM/80VO

0FM/80VO

Initial body weight (g)

65.3±2a

66.6±2a

65±0.8a

65.6±1a

65.4±0.8a

65.1±0.6a

Final body weight (g)

138.3±0.5b

142.1±4.4ab

139.4±2.0ab

147.6±1.9a

143.3±4.5ab

137.6±2.2b

Weight Gain (g/fish)

77.9±1.53b

80.3±3.4ab

79.5±1.35ab

87.1±2.9 a

82.9±6 ab

77.52±3.56b

Feed intake (g/fish)

76.3±1.2ab

76.5±1.86 ab

74.7±0.9b

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