Moderate exercise of rainbow trout induces only minor differences in fatty acid profile, texture, white muscle fibres and proximate chemical composition of fillets
Publication: Research - peer-review › Journal article – Annual report year: 2011
These experiments studied how moderate water velocities (0.9 body length second−1 (bl s−1)) may influence different quality characteristics of rainbow trout when compared to fish kept in standing water (b0.1 bl s−1). Fish fed at 1.3% of their body weight per day were slaughtered at a weight of 350 g after nine weeks of experiment at 15.0 °C. The fatty acid composition in fillets differed only marginally between exercised fish (excF) and control fish (ctrlF) kept in standing water. ExcF fillets had a significantly lower content of fatty acids 16:0 (Pb0.05) and 18:1 (n−7) (Pb0.01) and a higher content of 20:2 (n−6) (Pb0.05) compared to ctrlF fish, but all differences were small (b7%). The percentage of n−3 fatty acids was not significantly affected by the applied training regime and neither was the n−3 · n−6−1 ratio. The percentage of n−3 fatty acids, however, decreased linearly in both groups when the lipid content in the fillet increased (R2≥0.85, Pb1·10−6). Fillet texture measured instrumentally as shear force (g) after 72 h of ice storage did not differ between the two experimental groups, and neither did the content of lipid, protein or dry matter in the fillet. Muscle fibre sizes have a possible role in textural characteristics and were determined by histological analyses of white, glycolytic muscle tissue. These data showed that although differences in average fibre diameters were small (excF: 75.04 (s.d.=48.96)μm; ctrlF: 74.50 (46.21)μm) the general fibre size distribution differed significantly among the two groups (Pb0.01). Moreover, moderate exercise induced small but significant changes in fibre circularity (excF: circ.=0.724; ctrlF:=0.720, Pb0.05) but neither muscle fibre diameter nor circularity was significantly related to fillet texture. Altogether, the results suggest that moderate water velocities have limited impact on quality of pan-sized rainbow trout but subtle changes in the fillets indicate that other training strategies may induce stronger responses.
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- Histology, Quality, Water velocity, Fatty acids, n−3