Effects of dietary n‐6 polyunsaturated fatty acids on growth performance, body composition, haematological parameters and hepatic physiology of juvenile tiger puffer (Takifugu rubripes)

Abstract

A 74‐day feeding trial was conducted to investigate the efficacy of n‐6 polyunsaturated fatty acid (n‐6 PUFA) in diets for tiger puffer. Six experimental diets with graded levels of n‐6 PUFA (from 6.01 to 37.98 g/kg) replacing saturated fatty acids (SFAs) were used in this study. Increasing levels of n‐6 PUFA resulted in decreased weight gain (from 472.6% to 349.4%), feed efficiency and crude protein content in fish, but increased lipid accumulation in whole fish and liver. Liver samples from fish fed the lowest and highest level of n‐6 PUFA were subjected to transcriptomic assay. Analysis of the differentially expressed genes showed that high dietary levels of n‐6 PUFA tended to induce glycolysis and triacylglycerol biosynthesis, but reduce synthesis of amino acid and protein, and cause impairment to liver health. The mitochondrial DNA copy number, activity of mitochondrial respiratory chain complex I and glycogen content in the liver, which indicate energy supply status, significantly decreased with increasing levels of dietary n‐6 PUFA. In conclusion, high n‐6 PUFA/SFA ratios in diet led to reduced energy supply (by approximately 50%) and increased hepatic lipid accumulation (by 55%), which probably consequently negatively affect protein synthesis, liver health and growth of tiger puffer.

Arachidonic acid matters

“…Species‐specific difference in ARA essentiality could be a factor contributing to response variation. For example, a marine carnivore, tiger puffer ( Takifugu rubripes ), was susceptible to dietary ARA levels, and a very low ARA level (0.1%–0.3% d.w. or 1.4%–2.8% TFA) inhibited the growth 121 . Another contributing factor could also be that the dose‐dependent manner of ARA effects seemed to be size‐/age‐specific and also species‐specific, which was observed in most species demonstrating significant effects of ARA on the growth of juveniles and adults, but, for example, not in cobia, where excess ARA did not reduce growth or survival 105 .…”

“…For example, a marine carnivore, tiger puffer (Takifugu rubripes), was susceptible to dietary ARA levels, and a very low ARA level (0.1%-0.3% d.w. or 1.4%-2.8% TFA) inhibited the growth. 121 Another contributing factor could also be that the dose-dependent manner of ARA effects seemed to be size-/age-specific and also species-specific, which was observed in most species demonstrating significant effects of ARA on the growth of juveniles and adults, but, for example, not in cobia, where excess ARA did not reduce growth or survival. 105 Despite the inconsistent results currently available regarding the effects of dietary ARA on fish growth performance, the actual ARA requirements of aquaculture fish species still need to be estimated.…”

“…A multitude of ARA studies revealed decreased EPA deposition in fish in response to increasing dietary ARA levels. 17,20,22,73,[82][83][84]86,92,[94][95][96][97][98]104,105,[108][109][110][111][112][113][114]116,121,125,135,136,139,140,151,163,172,176,209,210 Therefore, no doubts should be present that increased dietary ARA displaces EPA retention in fish tissues.…”

“…First, a direct competition between ARA and EPA is present when they are incorporated into fish tissues, especially when incorporated into phospholipids and cellular membranes. A multitude of ARA studies revealed decreased EPA deposition in fish in response to increasing dietary ARA levels 17,20,22,73,82–84,86,92,94–98,104,105,108–114,116,121,125,135,136,139,140,151,163,172,176,209,210 . Therefore, no doubts should be present that increased dietary ARA displaces EPA retention in fish tissues.…”

The Importance of Fatty Acid Precision Nutrition: Effects of Dietary Fatty Acid Composition on Growth, Hepatic Metabolite, and Intestinal Microbiota in Marine Teleost Trachinotus ovatus

“…Since the only difference between D2 and D3 is that their lipid sources and corresponding fatty acid compositions are different, the better growth performance of D2 than D3 indicates the importance of dietary fatty acid composition and precise nutrition. It is well known that the levels of dietary LA and n-6 PUFA and DHA/EPA ratio compromise the healthy growth of fish [10,[21][22][23][24]. In this study, the LA and n-6 PUFA levels (of total fatty acids) and the DHA/EPA ratio of diet D2 (14.47%, 15.28%, and 1.08) are close to those of D1 (9.67%, 11.17%, and 0.92).…”