Li XiaoQin

Effect of dietary crystalline or microcapsuled lysine supplementation on growth and plasma total free amino acids of grass carp (Ctenopharyngodon idellus).

At present,more plant protein feedstuffs are used in aquatic feeds for the shortage and the increasing price of fish meal. The deficiencies of some essential amino acids (EAA) in plant protein feedstuffs lead to the addition of some EAA to balance diet composition. However,the effect of supplementing crystalline EAA was not positive for some fishes. As a result,the present experiment was conducted to investigate the effect of crystalline or microcapsuled lysine supplementation into practical diets on growth performance,and the total plasma free amino acids content of grass carp Ctenopharyngodon idellus. Four diets were prepared,which were high soybean meal(SM)diet with 23% SM,low SM diet with 15% SM,low SM diet added with crystalline or microcapsuled lysine,which had the same lysine content as high SM diet respectively. Grass carp (49.0±2.0) g were fed the four diets with triplicate for 8 weeks. Growth rates(GR) of the four groups were 279.3%,239.7%,245.6%,277.5%,feed coefficient(FC) were 1.62,1.88,1.85,1.64,respectively. Compared with low SM group,adding crystalline lysine in diet had no significant effects on growth performance,but the growth rate was improved by 15.8% and FC decreased by 0.24 (P0.05) by adding microcapsuled lysine in diet. Fish fed on low SM added with microcapsuled lysine had the same GR and FC as those of high SM group(P0.05). Plasma total free amino acids(TFAA) concentration at 0,1,2,3,4,5 h after feeding were determined,and the highest concentration of TFAA occurred at 3 h after feeding for high SM diet,low SM diet added without or with microcapsuled lysine,but absorbing peak occurred at 2 h after feeding for low SM diet added with crystalline lysine,which means the absorbing peak was advanced. Leaching loss of crystalline and microcapsuled lysine were 69.82% and 19.81%,which indicated leaching loss of crystalline lysine was significantly decreased by microcapsuling. Results above showed that grass carp fed with diet supplemented with microcapsuled lysine had a slower absorbing peak of serum TFAA than that fed with crystalline lysine. Microcapsuled lysine had a lower leaching loss in water than crystalline lysine. Growth rate of grass carp could be improved,FC decreased by adding microcapsuled lysine in low SM practical diet,but was not affected by crystalline lysine.

茶多酚对奥尼罗非鱼生长、消化功能、免疫性能和抗病力的影响

本试验旨在研究茶多酚对奥尼罗非鱼（Oreochromis niloticus×O. aureus）生长、消化功能、免疫性能和抗病力的影响。在基础饲料中分别添加0（对照组）、100、200、400、600、800 mg/kg茶多酚，配制6种试验饲料，饲喂初始体重为（6.09±0.07）g的奥尼罗非鱼9周，每组3个重复，每个重复25尾鱼。结果表明：与对照组相比，各茶多酚添加组的增重率和饲料系数均无显著变化（P>0.05），但100、200 mg/kg茶多酚组增重率有提高的趋势，而400~800 mg/kg茶多酚组增重率有降低的趋势，其中以200 mg/kg茶多酚组增重率最高。饲料添加茶多酚对罗非鱼全鱼水分、粗蛋白质、粗灰分含量和粗蛋白质表观消化率无显著影响（P>0.05），但与对照组相比，高添加量（600、800 mg/kg）的茶多酚显著降低了干物质表观消化率，肠道淀粉酶、蛋白酶活性和全鱼粗脂肪含量（P<0.05）。与对照组相比，饲料中添加200、400、600和800 mg/kg茶多酚均显著增加了血清超氧化物歧化酶（SOD）和溶菌酶（LZM）活性（P<0.05），而血清丙二醛（MDA）含量则随茶多酚添加量的增加表现出先降低后增加的趋势，其中200 mg/kg茶多酚组的血清SOD活性最高、血清MDA含量最低，400 mg/kg茶多酚组的血清LZM活性最高。嗜水气单胞菌攻毒后48和96 h，200、400、600和800 mg/kg茶多酚组的累积死亡率均较对照组显著降低（P<0.05），其中400 mg/kg茶多酚组的累积死亡率最低。综上，茶多酚可提高奥尼罗非鱼的免疫性能，降低嗜水气单胞菌攻毒后的死亡率，但对生长性能没有显著影响。奥尼罗非鱼饲料中茶多酚的建议添加量为200~400 mg/kg。