Changes in fatty acid composition in muscle and adipose tissue of farmed rainbow trout (Oncorhynchus mykiss) in relation to ration and age

To evaluate the importance of age and feed ration level (RL) on the composition of tissue fatty acid (FA) in rainbow trout (Oncorhynchus mykiss), fish were fed rations ranging from appreciable underfeeding to gross overfeeding in a longitudinal experiment lasting from start of feeding to onset of sexual maturation 2.4 years later. In order to study the effects of compensatory growth and reduced feed availability, fish were moved from high to low ration and vice versa. Changes of individual FA of total lipid (TL), triacylglycerols (TAG) and total phospholipids (PL) were studied in white and red muscle, as well as in three major adipose tissues. The effect of saltwater transfer on FA composition was also examined. A strong interdependence was found between the relative proportion of PL and TAG with changes in TL content. This was most prominent in white muscle. In parallel with this change in relative lipid class composition, a major effect was seen on FA in the TL fraction. The most marked effect of RL was an inverse relationship between 22:6 n-3 of the PUFA n-3 series and 16:1 and 18:1 of the MUFA series. This was seen in all tissues studied. II is suggested that the most important factor governing FA composition in muscle, pending changes in feed intake, is the TL content, affecting the relative level of PL and TAG. In adipose tissue, consisting mainly of TAG, more subtle changes were observed. The FA compositions of PL and TAG were not affected to any major extent by RL, except at extreme reductions. Significant changes in FA of PL and TAG were observed as an effect of saltwater transfer. (C) 2001 Elsevier Science Ltd. All rights reserved.