宠物级鸡肉粉替代鱼粉的饲料中补充苏氨酸对大口黑鲈生长性能、糖脂代谢和免疫的影响

试验采用初始体重为4.16±0.06g的大口黑鲈(Micropterus salmoides)作为研究对象,设计3种等氮等脂的饲料：苏氨酸对照组(TC,65.0%鱼粉),低苏氨酸组(LT,65.0%宠物级鸡肉粉添加除苏氨酸以外的必需氨基酸至TC水平组)和苏氨酸添加组(TS,LT组添加苏氨酸至TC水平组),探究饲料中不同苏氨酸水平对大口黑鲈生长性能、糖脂代谢、免疫及宠物级鸡肉粉利用率的影响,养殖试验开展8周。试验结果表明：与对照组相比,LT处理组饲料显著降低了大口黑鲈的生长性能、饲料效率和鱼体营养物质组成(P<0.05),饲料中添加苏氨酸可在一定程度上改善宠物级鸡肉粉完全替代鱼粉后导致的生长性能受限、饲料效率低下和鱼体营养物质组成降低等问题(P<0.05)。宠物级鸡肉粉完全替代鱼粉还显著降低了血浆中营养成分和多种游离氨基酸的含量(P<0.05),饲料中添加晶体苏氨酸能够显著提高血浆中游离氨基酸的水平(P<0.05),使之与对照组间无显著性差异(P>0.05)。mRNA水平上,饲料中苏氨酸添加可显著改善鸡肉粉完全替代鱼粉引起的肝脏中糖脂合成代谢抑制和分解代谢加剧的现象,同时苏氨酸添加也可显著降低细胞炎症因子的mRNA的表达水平(P<0.05)。综上所述：饲料中适量苏氨酸的添加可在一定程度上提高大口黑鲈的生长性能、促进脂肪合成和抑制脂肪分解,并增强的免疫机能。

Effects of threonine supplementation in poultry by-product meal (petfood grade) replacement diet on growth performance, intermediary metabolism and immunity response in largemouth bass (Micropterus salmoides)

Largemouth bass (Micropterus salmoides) with an initial body weight of 4.16±0.06g was used in present study to explore the changes of growth performance and metabolism after the fish fed with three different isonitrogenous and isolipid diets (TC diet: threonine control group, LH diet: low threonine group and TS diet: threonine supplementation group) for 8 weeks. Present results showed that compared with the TC diet, the LH diet significantly decreased the growth performance, feed efficiency and body nutrient composition (P< 0.05), threonine addition could promote those differential effects caused by fishmeal totally substituted by poultry by-product meal (P<0.05). Moreover, the LH diet also suppressed the concentration of plasma nutrients and free amino acids than the control diet (P<0.05). TS diet had significant effects on elevating the plasma free amino acids concentration (P< 0.05) and made no notable difference compared to the TC diet (P>0.05). The mRNA expression level demonstrated that threonine supplementation markedly ameliorated the inhibition of anabolism, aggravation of catabolism and cellular inflammatory which caused by complete replacement of fishmeal with poultry by-product meal (P< 0.05). In conclusion, appropriate threonine supplementation could promote the growth performance by improving nutrient anabolism and immune response and inhibiting catabolism in largemouth bass.