G. ZHELYAZKOV1, T. POPOVA2 and Y. STAYKOV1
1 Trakia University, Department of Biology and Aquaculture, Faculty of Agriculture, BG – 6000 Stara Zagora, Bulgaria
2 Institute of Animal Sciences, Department of Ecology and Quality of Animal Production, BG – 2232 Kostinbrod, Bulgaria
ZHELYAZKOV, G., T. POPOVA and Y. STAYKOV, 2015. Effect of sunflower and linseed oil supplementation in the diet on the chemical and fatty acid composition of rainbow trout (Oncorhynchus mykiss W.), cultivated in recirculating system. Bulg.J. Agric. Sci., Supplement 1, 21: 161–168
The aim of this study was to determine the influence of the dietary linseed and sunflower oil supplementation on the chemical and fatty acid composition in the meat of rainbow trout (Oncorhynchus mykiss W.), cultivated in recirculating system. The fish in the experiment received extruded pellets and were divided in control (CG) and two experimental groups – EL and ES. The feed of the rainbow trout of EL group was supplemented with 5% linseed oil and that of the group ES contained additionally 5% sunflower oil. The fish of the control group did not receive any of the above mentioned oils as additives. At the end of the 60 day trial period, four fish of each group were randomly selected for evaluation of the chemical and fatty acid composition in the fillet. Significant influence of the vegetable oils in the diet on the water content of the fillets was found (P ≤ 0.05) as the group fed linseed oil showed the highest value of this parameter in comparison with the fish of the control group and the group receiving sunflower oil. Supplementation with both oils led to significantly higher protein content in the meat of the two experimental groups, compared to this one of the fish of the control (Р ≤ 0.001), while the value of the dry matter was lower in the fillets of the group with the linseed oil in the diet, compared to this parameter of fish from C and ES (Р ≤ 0.05). The linseed and sunflower oils in the diet of the rainbow trout influenced significantly the contents of С16:0 (P ≤ 0.05), С18:2 (P ≤ 0.01) and С18:3 (P ≤ 0.001) in the fillets. The fish receiving sunflower oil as feed additive displayed highest levels of С18:2, compared to these parameters in the fish of C and EL groups. The group with linseed oil supplementation in the diet had lower content of C16:0 and higher value of C18:3 content than the fish fed pellets supplemented with sunflower oil and the control group. The changes in the individual fatty acids in the fish of experimental groups EL and ES corresponded to those of their total amounts – the content of n-6 PUFA was highest in the group fed with added sunflower oil (Р ≤ 0.05), while the rainbow trout receiving diet, supplemented with linseed oil had highest total content of n-3 PUFA (Р ≤ 0.01). The vegetable oils influenced the values of n-6/n-3 ratio (P < 0.001) which were significantly higher in the fish of ES group, when compared to these ones in the fillets from the control and linseed oil groups.