蛋氨酸缺乏对蛋鸡产蛋后期生产性能、血清游离氨基酸含量和肝脏蛋氨酸代谢相关基因表达的影响

本试验旨在研究蛋氨酸缺乏对蛋鸡产蛋后期生产性能、血清游离氨基酸含量和肝脏蛋氨酸代谢相关酶基因表达的影响。选取180只62周龄的海兰灰蛋鸡,根据产蛋率均匀分成3组(每组6个重复,每个重复10只):对照组饲喂蛋氨酸水平为0.33%的饲粮,蛋氨酸缺乏组分别饲喂蛋氨酸水平为0.21%和0.27%的饲粮,试验期90d。结果表明:1)饲粮蛋氨酸缺乏显著降低了蛋鸡的平均日采食量、产蛋率、平均日产蛋重、平均蛋重和不合格蛋率(P0.05),显著提高了料蛋比(P0.05)。2)蛋氨酸缺乏显著降低蛋鸡血清中蛋氨酸的含量(P0.05)。0.21%蛋氨酸组蛋鸡血清中丝氨酸、甘氨酸和丙氨酸的含量显著高于其他2组(P0.05)。0.27%蛋氨酸组蛋鸡血清中缬氨酸、异亮氨酸和精氨酸的含量显著低于对照组(P0.05),脯氨酸的含量显著低于0.21%蛋氨酸组(P0.05)。3)与对照组相比,0.21%蛋氨酸组蛋鸡肝脏中DNA甲基转移酶1、N6-甲基腺苷(m6 A)甲基转移酶3(METTL3)和m6 A甲基转移酶14的表达量显著提高(P0.05),0.27%蛋氨酸组蛋鸡肝脏中METTL3的表达量显著提高(P0.05)。4)与对照组相比,0.21%蛋氨酸组蛋鸡肝脏中甲硫氨酸腺苷转移酶1a、5-甲基四氢叶酸-同型半胱氨酸甲基转移酶(MTR)和胱硫醚-β-合成酶的表达量显著提高(P0.05),0.27%蛋氨酸组蛋鸡肝脏中MTR的表达量显著提高(P0.05)。蛋氨酸缺乏对蛋鸡肝脏甲硫氨酸腺苷高半胱氨酸酶和甜菜碱高半胱氨酸甲基转移酶的表达量无显著影响(P0.05)。由以上结果可知:蛋鸡饲粮高水平的蛋氨酸缺乏会降低蛋鸡的生产性能,可能与蛋氨酸缺乏改变蛋氨酸代谢途径,影响DNA和RNA的甲基化过程有关。

Effects of Methionine Deficiency on Performance,Serum Free Amino Acid Contents and Liver Methionine Metabolism Gene Expression of Laying Hens during Late Period of Laying

This experiment was conducted to study the effects of methionine deficiency on performance,serum free amino acid contents and liver methionine metabolism gene expression of laying hens during late period of laying.Based on the egg production,a total of 180 Hy-Line Grey laying hens at 62 weeks of age were allocated to 3 groups with 6 replicates each and 10 hens in each replicate.Hens in three groups were fed different diets which contained 0.21%,0.27% and 0.33% (control group) methionine,respectively,and the experiment period was 90 days.The results showed as follows: 1) dietary methionine deficiency significantly reduced the average daily feed intake,laying rate,average daily egg production,average egg weight and unqualified rate of eggs (P<0.05),but significantly increased the ratio of feed to egg of laying hens (P<0.05).2) Methionine deficiency significantly reduced the serum methionine content of laying hens (P<0.05).The contents of serum serine,glycine and alanine in 0.21% methionine group were significantly higher than those in the other two groups (P<0.05).The contents of serum valine,isoleucine and arginine in 0.27% methionine group were significantly lower than those in control group (P<0.05),and serum proline content in 0.27% methionine group was significantly lower than that in 0.21% methionine group (P<0.05).3) Compared with control group,the expression levels of DNA methyltransferase 1,N6-adenosine-methyltransferase subunit 3 (METTL3) and N6-adenosine-methyltransferase subunit 14 in liver of hens in 0.21% methionine group were significantly improved (P<0.05),and the METTL3 expression level in liver of hens in 0.27% methionine group was also significantly improved (P<0.05).4) Compared with control group,the expression levels of methionine adenosyltransferase 1a,cystathionine-beta-synthase and 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR) in liver of hens in 0.21% methionine group were significantly improved (P<0.05),and the MTR expression level in liver of hens in 0.27% methionine group was also significantly improved (P<0.05).Methionine deficiency had no significant influence on the expression levels of adenosylhomocysteinas and betaine homocysteine methyltransferase in liver of hens (P>0.05).In conclusion,dietary methionine deficiency reduces performance of hens which may duo to the change of methionine metabolism pathway and the methylation of DNA and RNA.