Increasing dietary SFA:MUFA ratio with low levels of LC-PUFA affected lipid metabolism, tissue fatty acid profile and growth of juvenile California Yellowtail (Seriola dorsalis)

Abstract

Lipids rich in saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) are among the alternative sources reported to maintain growth and tissue fatty acid composition and, in some cases, reducing the long-chain polyunsaturated fatty acids (LC-PUFA) requirements. The present works aims to investigate the effects of different SFA:MUFA ratios on growth performance, tissue fatty acid composition, and the expression of crucial genes involved in the lipid metabolism of juvenile California Yellowtail (Seriola lalandi) fed diets with increasing SFA:MUFA ratios (1.6, 1.8, and 2.0) with low LC-PUFA levels. After eight weeks, fish fed the control diet outperformed the experimental feeds with increasing SFA:MUFA ratio in terms of final weight, specific growth rate, and liver index. No differences were observed in survival, viscerosomatic index, and condition factor across dietary treatments. Whole-body, liver, and muscle tissues proximate composition was slightly affected by increasing the dietary SFA:MUFA ratio. In terms of fatty acid composition, whole-body, liver, and muscle tissues reflected the dietary fatty acid composition to most extent, except SFA (mainly 16:0) that was not proportionally deposited. LC-PUFA sparing effect was demonstrated at a low degree in this study, likely due to the low SFA:MUFA ratio or high content of dietary MUFA. Significant changes were observed in the expression of genes related to lipid metabolism. The ppara and igf1 expression were higher in fish fed the Control diet than those fed SFA:MUFA 1.6 diet. Whereas the fish from SFA:MUFA 1.6 group displayed higher cptla expression compared to fish from SFA:MUFA 2.0.