Evaluation of long‐chain n3 fatty acid content in diploid and triploid rainbow trout

Abstract

Intake of long chain n3 fatty acids (LCn3), eicosapentaenoic acid (EPA; 20:5 n3) and docosahexaenoic acid (DHA; 22:6 n3), is associated with reduced cardiovascular disease. There is growing interest in farmed fish like rainbow trout, Oncorhynchus mykiss, as sources of LCn3. The trout industry raises diploid (2N) and triploid (3N) fish. 3N females fail to sexually mature and avoid the negative effects of maturation on fillet quality. In this work we examined the LCn3 content of 2N and 3N trout. Female rainbow trout were selected from independent populations of 1 yr and 2 yr old 2N and 2 yr old 3N fish. Although each group consumed the same diet formulation, rearing conditions and feeding rates were different and only the 2 yr 2N trout were sexually mature. Boneless, skinless fillets were removed from 4 fish per group and the total fatty acid content of the fillets was determined by FAME analysis. The contents of LCn3 in the 3N 2yr trout (EPA: 1.9 ± 0.5 mg/g; DHA 7.6 ± 1.7 mg/g) were almost 2‐fold higher than in the 2N 2yr trout (EPA:0.8 ± 0. mg/g; DHA 3.9 ± 0.5 mg/g) and the 2N 1yr trout (EPA:1.0 ± 0.3 mg/g; DHA 4.0 ± 0.7 mg/g). The higher content of LCn3 was in part the result of total higher content of fatty acid in the 3N trout. The percent content of LCn3 and ratios of short chain to long chain n3 were similar in all groups. These data indicate that farm‐raised rainbow trout are a rich source of EPA and DHA. This work was supported by the USDA‐ARS.