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本试验旨在探讨脂肪和L-肉碱对大口黑鲈饲料中蛋白质的节约作用。采用3×2(蛋白质脂肪比×L-肉碱)完全随机设计,配制了不同蛋白质脂肪比(39.9%/7.4%、30.3%/13.9%和21.5%/19.5%)和L-肉碱水平(0和1g/kg饲料)的6种等能饲料。选取平均初重为(3.27±0.21)g的大口黑鲈幼鱼270尾,随机分为6组(每组3个重复,每个重复15尾),随机饲喂1种饲料,试验期6周。结果表明:随着饲料中脂肪水平从7.4%升高到19.5%(蛋白质水平从39.9%下降到21.5%),鲈鱼的增重率从685%显著降低到176%(P<0.05),饲料效率从1.15增加到2.33(P<0.05),且投喂蛋白质脂肪比为21.5%/19.5%饲料的鲈鱼的肥满度显著低于投喂蛋白质脂肪比为39.9%/7.4%和30.3%/13.9%饲料的鲈鱼(P<0.05)。投喂蛋白质脂肪比为21.5%/19.5%饲料的鲈鱼体水分含量显著低于投喂蛋白质脂肪比为39.9%/7.4%的饲料(P<0.05),且随着饲料中脂肪水平从7.4%升高到19.5%(蛋白质水平从39.9%下降到21.5%),全鱼脂肪含量从5.6%显著升高到11.5%(P<0.05),全鱼粗蛋白质含量从15.6%显著下降到10.4%(P<0.05)。鱼体肝脏和肌肉中脂肪含量以及肝体指数在投喂蛋白质脂肪比为21.5%/19.5%饲料时达到最高值。此外,随着饲料中脂肪水平从7.4%升高到19.5%(蛋白质水平从39.9%下降到21.5%),淋巴细胞百分比由38.30%升高到48.41%(P<0.05),粒细胞百分比由51.75%下降到42.14%(P<0.05)。由此得出,以节约蛋白质为目的的过量添加脂肪会导致鱼体生长速度降低,甚至引起脂肪肝的发生和机体免疫系统的应激反应。此外,饲料中添加1g/kg的L-肉碱并不能提高大口黑鲈的生长性能,但蛋白质脂肪比和L-肉碱对淋巴细胞百分比和粒细胞百分比存在互作作用,并在饲喂添加1g/kgL-肉碱的蛋白质脂肪比为21.5%/19.5%的饲料时达到峰值。
The purpose of this study was to investigate the effect of fat and L-carnitine on protein conservation in largemouth bass feed. Using a completely randomized design with 3 × 2 (protein to fat × L-carnitine), different protein fat ratios (39.9% / 7.4%, 30.3% / 13.9% and 21.5% / 19.5%) and L-carnitine levels 0 and 1g / kg feed) 6 kinds of can feed. A total of 270 juvenile largemouth bass, with an average initial weight of (3.27 ± 0.21) g, were randomly divided into 6 groups (3 replicates in each group, 15 in each replicate). The results showed that the weight gain of seabass decreased significantly from 685% to 176% (P <0.05) as the level of fat in feed increased from 7.4% to 19.5% (protein level decreased from 39.9% to 21.5%), feed efficiency From 1.15 to 2.33 (P <0.05), the sea bass fed with protein-fat ratio of 21.5% / 19.5% had a significantly lower fatness than the fed-fat ratio of 39.9% / 7.4% and 30.3% / 13.9% Seabass fed (P <0.05). The body water content of sea bass fed with protein fat ratio of 21.5% / 19.5% was significantly lower than that fed with protein / fat ratio of 39.9% / 7.4% (P <0.05), and with the increase of fat level from 7.4% (P <0.05). The crude protein content of whole fish decreased significantly from 15.6% to 10.4% (P <0.05) <0.05). The fat content in the liver and muscle of fish body and the liver body index reached the highest value when the protein fat ratio was 21.5% / 19.5%. In addition, the percentages of lymphocytes increased from 38.30% to 48.41% (P <0.05), and the percentage of granulocytes increased from 51.75 (P <0.05) as the dietary fat level increased from 7.4% to 19.5% (protein level decreased from 39.9% to 21.5% % To 42.14% (P <0.05). It is concluded that the excessive protein added for the purpose of saving protein will lead to the reduction of the growth rate of the fish and may even cause the occurrence of fatty liver and the stress response of the body’s immune system. In addition, the addition of 1 g / kg L-carnitine to the diet did not improve growth performance in largemouth bass, but protein-to-fat ratio and L-carnitine had an interaction with lymphocyte percentage and granulocyte percentage, The protein-fat ratio of 1 g / kg L-carnitine peaked at 21.5% / 19.5% feed.