Effect of linseed and sunflower oils in the diet on the growth parameters in rainbow trout (Oncorhynchus mykiss W.) cultivated in a recirculating system

G. Zheliazkov*

Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

Abstract. The aim of this study was to determine the influence of linseed and sunflower oils in the diet on the survival rate, weight gain and the feed conversion ratio in rainbow trout, reared in a recirculating system. The fish of the three groups were raised in concrete tanks with effective capacity of 0.8 m3, which were part of the recirculating system. Rainbow trout received extruded feed (6 mm pellets), produced by “Aqua garant”. The feed of the fish from the experimental group (EL) was supplemented with 5% linseed oil, while that of the trout of the group (ES) – 5% sunflower oil. The diet of the fish of the control group (C) did not contain any of the above mentioned oils. The duration of the trial was 60 days. In order to study the effect of linseed and sunflower oils in the diet on the weight gain of the fish, control catches were carried out at 15 days’ interval. The live weight (g) and linear growth (mm) of the control catches were determined as the fish were individually weighed and measured. The final live weights of the trout in the experimental groups as well as that in the control were as follows: EL – 334.79±67.52g, ES – 329.39±70.31 g and C – 323.58±67.77 g. The values of this parameter in EL were higher than those of fish from ES and the control group by 1.64% and 3.47%, respectively, but the differences were not significant (P>0.05). This trend persisted also for the linear measurements – in the trout of EL they were the highest. The fish of EL displayed the lowest feed consumption. This trait had lower values than the ones of the trout of ES and the control group by 2.84% and 5%, respectively, though the differences were not significant (P>0.05). The survival rate of the fish from the groups did not differ substantially.

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Effect of linseed and sunflower oil supplementation in the diet on the growth performance in carp (Cyprinus carpio L.), cultivated in a recirculating system

Abstract. The aim of this study was to determine the influence of linseed and sunflower oil supplementation on the survival rate, weight gain and feed conversion ratio in carp (CyprinuscarpioL.), raised inarecirculating system. The fish in the experiment were reared in concrete tanks that were part of the recirculating system and had a capacity of 0.8 m3. The carps received extruded pellets (6 mm) obtained by “Aqua garant”. For a period of 60 days the feed of the fish of the experimental group (EL) was supplemented with 5 % linseed oil, while the carps of the group (ES) received additionally 5 % sunflower oil with the diet. The fish of the control group (C) received feed without any of the above mentioned vegetable oils. The weight gain of the carps was controlled at 15-days intervals. The live weight (g) and the linear growth (mm) were determined as the fish were weighed and measured individually. The final live weight of the carps of the experimental and control groups was as follows: EL–871.45±240.39 g, ES–849.00±223.22 g and C–819.55±269.91 g. The value of this parameter in the fish of EL groups was by 2.58% and 5.96% higher than those of the individuals of ES and C groups, respectively, but the differences were not significant (P>0.05). This tendency was similar for the linear measurements, as in the carps receiving linseed oil they were the highest. The EL group displayed the lowest feed consumption. The value of this parameter was lower than those of the ES and C groups by 13.90% and 25.74%, respectively. The differences were significant between the control group and the carps supplemented with linseed oil (P<0.05). The survival rate in the fish of the three groups did not differ significantly.

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