Arachidonic acid modulated lipid metabolism and improved productive performance of striped bass (Morone saxatilis) juvenile under sub to optimal temperatures

The present study aimed to investigate the effects of different dietary arachidonic acid (ARA) levels on lipid metabolism, productive performance and biological indexes of striped bass exposed to different temperatures. Within this purpose, four isoproteic (44% of crude protein) and isolipidic (11% of lipid) experimental diets were formulated based on defatted meals and different lipid sources. Fish oil was used as primary lipid source in the control diet (FO), whereas a mixture of coconut, peanut, eicosapentaenoic acid (EPA) and docosaexaenoic acid (DHA) oils, and different amount of ARA was added to three experimental diets (ARA1–0.3%, ARA2–0.7%, and ARA3–1.2%). Additionally to the ARA, differences in the levels of specific fatty acids as 16:0, 16:1, 18:1n-9 and EPA were observed between FO and ARA diets. Morone saxatilis (striped bass) juveniles (5.31 ± 0.18 g), were distributed (30 fish) into each tank (12; with 500 L water volume) in triplicate groups. All fish were exposed to the same temperature, which was raised every fourteen days to a higher temperature (14, 18, 22, and 26 °C). All dietary treatment remained 14 days at each temperature and an additional seven acclimation days to the new temperature. After seventy-seven days of the feeding trial, a decrease in growth and mainly survival rate were observed in fish fed the FO diet, compared to the rest of the treatments. Our results suggested that different diets composition, mostly higher dietary ARA influenced greater feed intake, weight gain, and especially survival. ARA was efficiently retained in liver and fillet at higher temperatures, while at lower temperatures, it was probably synthesized in other compounds, such as prostaglandins. Additionally, the temperature rise influenced a higher lipid deposition in hepatocytes of animals from all experimental groups. Dietary ARA and temperature modulated the expression of genes related to the prostaglandin synthesis and fatty acid synthesis and catabolism. It is concluded that ARA, such as DHA, is an essential fatty acid needed at higher levels (0.7 to 1.2% in diet), especially when fish is exposed to low sub-optimal temperatures. While when fish oil was used in the control diet (containing 0.33% ARA), fish not only decrease in body mass but compromise its physiological status, resulting in mass mortalities when the temperature reached the optimum range for this species.