为研究饲料钾水平对低盐海水养殖的凡滨对虾生长和生理指标的影响，本试验在基础饲料中分别添加0%、0.3%、0.6%、0.9%、1.2%和1.5%的钾，投喂生长在4度海水中的凡纳滨对虾8周。结果表明，除0.6%组外，各处理组增重率和特定生长率均无显著差异（P＞0.05）。血清谷草转氨酶、谷丙转氨酶活力表现为随饲料中钾添加量的增加呈先升高后降低的趋势；对照组、0.3%组和0.6%组间的尿素氮水平无显著差异（P＞0.05），但显著高于其余各组（P＜0.05）；随饲料钾添加量的增加，0.9%组腮丝Na+-Ka+-ATP酶活力显著高于其他各组（P＜0.05）。随饲料钾的添加量增加，免疫酶活性表现为先上升后下降的趋势。综上所述，4度海水条件下，基础饲料含钾0.788%时，钾添加水平不影响凡纳滨对虾的生长；饲料中添加0.6%~0.9%的钾，对虾可获得最佳的氮代谢、渗透调节能力和免疫力。%The aim of this study was to examine the effect of the dietary potassium level on the growth performance and physiological indices of Litopenaeus vannamei reared in 4 diluted seawater.Shrimp were fed diets containing six grad-ed levels of potassium (0%,0.3%,0.6%,0.9%,1.2%and 1.5%)for 8 weeks.The results showed that there were no signifi-cant difference of weight gain rate and specific growth rate among treatments except 0.6% group.Aspartate aminotrans-ferase,alanine aminotransferase activities in serum increased first and then decreased with the dietary potassium level in-creased.Urea nitrogen level in serum of control,0.3%and 0.6%groups had no significant difference (P>0.05),but sig-nificantly higher than that of others (P < 0.05).The total protein content in serum reduced while the K+supplement in-creased.Na+-Ka+-ATPase activity in gill filaments of 0.9% group was significantly higher than that of other groups (P <0.05).Immune enzymes activity roughly increased at first and then decreased with the dietary potassium level increasing.In summary,dietary potassium level didn’t affect the growth performance of Litopenaeus vannamei,which reared in 4 degree seawater with basic diet containing 0.788%potassium.The best nitrogen metabolism,osmotic adjustment ability and immu-nity could be obtained when the potassium adding level in feed was from 0.6%to 0.9%.
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