牙鲆幼鱼对EPA和DHA的营养需求

研究了EPA和DHA水平对牙鲆生长的影响,饲料中含0.5%EPA和1.0%～1.5%DHA能保证牙鲆幼鱼最适生长,鱼体水分最低,肝体指数最小,脂肪含量有较大幅度提高,肝脏极性脂中EPA和DHA达到最大积累;在肝脏和肌肉的非极性脂部分,各组间的脂肪酸组成没有显著变化,而极性脂部分能体现出饲料中n-3 HUFA含量对鱼体脂肪酸组成的影响,极性脂中的EPA和DHA含量远高于非极性脂;在肌肉和肝脏的极性脂和非极性脂中都含有较高的16:0和18:1n-9; 18:1n-9/n-3HUFA可以作为必需脂肪酸满足程度的一个判据,18:1n-9值的升高往往是缺乏必需脂肪酸的表现,在生长最佳时18:1n-9/n-3HUFA比值下降,为0.62和0.74.

Nutrient requirements for EPA and DHA by juvenile Paralichthys olivaceus

Juvenile Japanese flounders were fed with purified diets containing different levels of eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3,DHA) to determine the effects of the both fatty acids on fish growth performance. Combining the growth data with the analysis of fatty acid composition of muscle and liver, it was indicated that the optimum requirement for EPA and DHA are 0.5% and 1.0%-1.5%, respectively. Under the conditions, the fish fed with diet 5 and diet 6 showed highest growth rate, lowest muscle moisture and HI, higher muscle lipid content and highest EPA, DHA accumulation in the polar lipid fraction of the liver. However, in the non-polar lipid fraction of the liver and muscle, the compositions of fatty acid showed no significant difference between the groups. So the contents of polar lipid fraction could indicate the effects of n-3 HUFA on fatty acid composition of fish muscle, and EPA, DHA contents in the polar fraction were much higher than those of non-polar fraction. Either in liver or in muscle, the contents of 16:0 and 18: 1n-9 were quite high both in polar and non-polar lipid fraction. So the ratio of 18: 1n-9 and n-s HUFA could determine if the diet EFA contents could meet the requirements. The ratio will reduce when fish grows well, in the present experiment, the fish fed diet 5 and diet 6 showed lowest 18: 1n-9/n-3HUFA, they were 0.62 and 0.74, respectively.