Effects of DHA and EPA ratios in dietary on sex steroid hormone and reproduction performance in female starry flounder(Platichthys stellatus)
In order to investigate the effects of docosahexaenoic acid(DHA)and eicosapentaenoic acid(EPA)ratios in dietary on sex steroid hormone and reproduction performance in female starry flounder(Platichthys stellatus),five isonitrogenous and isolipidic experimental diets were formulated to contain different DHA and EPA ratios(0.65,1.33,2.12,3.08 and 3.92),each group has 3 duplication.Fish were reared in an indoor flowing seawater system and lasting 90 d.At the end of the feeding trial,sex steroid hormone production was assayed and gonad samples from females were collected to determine the gene expressions of sex steroid-synthesizing proteins.The results showed that the estradiol production in females increased and then decreased with higher DHA and EPA ratios,promotion significantly and increased the mRNA expression of FSHR、StAR and aromatase in ovaries significantly when DHA and EPA ratios at 1.33(P＜0.05).Female broodstock gonadosomatic index,absolute fecundity,relative fecundity increased significantly after adding DHA and EPA,and obtained better results in DHA and EPA ratios group 1.33 compared with the control group.In ovaries,the content of monounsaturated fatty acids(MUFA)in group 0.65,1.33 and 2.12 was significantly higher than other groups(P＜0.05);Meanwhile n-6 polyunsaturated fatty acid(PUFA)decreased significantly compared to the control group and n-3 PUFA increased significantly as well(P＜0.05).In conclusion,DHA and EPA adding promoted female starry flounder gonad development and increased the estradiol production in females effectively.The mRNA expression of FSHR、StAR and aromatase and absorption of MUFA and increased the energy supply of gonad development only when DHA/EPA ratios at 1.33 as well as promoting the maturation of the gonads and improving reproduction performance of females.
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