苜草素对蛋鸡胆固醇代谢的影响及其基因调控机制

本试验旨在研究饲粮中添加不同水平苜草素对蛋鸡胆固醇代谢的影响,并探讨其基因表达调控机制。选取体重和产蛋率相近的26周龄尼克蛋鸡540只,随机分为5组,每组6个重复,每个重复18只。对照组饲喂基础饲粮,试验组分别在基础饲粮中添加300、600、900、1 200 mg/kg的苜草素。预试期7 d,正试期70 d。结果表明:1)试验第35天和第70天,900 mg/kg苜草素组的蛋黄胆固醇含量显著低于对照组(P0.05)。2)与对照组相比,900 mg/kg苜草素组显著升高了蛋鸡血清中高密度脂蛋白胆固醇(HDL-C)含量和高密度脂蛋白/低密度脂蛋白(HDL/LDL)(P0.05),各组蛋鸡血清中总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)含量差异均不显著(P0.05)。3)与对照组相比,600、900、1 200 mg/kg苜草素组显著降低了蛋鸡肝脏中3-羟基-3-甲基戊二酸单酰辅酶A还原酶(HMGCR)mRNA表达量(P0.05),900和1 200 mg/kg苜草素组显著升高了蛋鸡肝脏组织中胆固醇7α-羟化酶(CYP7A1)mRNA表达量(P0.05)。各组蛋鸡肝脏中固醇结合蛋白元件-2(SERBP-2)和卵巢中卵黄蛋白原受体(OVR)mRNA表达量无显著差异(P0.05)。综上,饲粮中添加苜草素降低了蛋黄胆固醇和全蛋胆固醇含量,其调控机制可能是通过抑制蛋鸡胆固醇的内源性合成和促进胆固醇向胆汁酸的转化排泄2种途径来实现。本试验推荐26~35周龄蛋鸡苜草素添加水平为900 mg/kg。

Effects and Gene Regulatory Mechanism of Polysavone on Cholesterol Metabolism of Laying Hens

The experiment was carried out to evaluate the effects of dietary different polysavone supplemental level on cholesterol metabolism of laying hens, and discussed its regulation mechanism of gene expression. A total of 540 twenty?six?week?old Nick laying hens were randomly divided into 5 groups with 6 replicates per group and 18 birds per replicate. Laying hens in control group were fed with a basal diet, and other were fed with the basal diets supplemented with 300, 600, 900 and 1 200 mg/kg polysavone, respectively. The pre?test lasted for 7 days, and the experiment lasted for 70 days. The results showed as follows:1) on day 35 and day 70, the yolk cholesterol content in 900 mg/kg polysavone group was significantly lower than that in control group (P<0.05). 2) Compared with the control group, the high density lipoprotein?cholesterol (HDL?C) content and high density lipoprotein to low density lipoprotein ratio ( HDL/LDL ) in 900 mg/kg polysavone group significantly increased ( P<0.05) . There were no significant differences in the contents of total cholester?ol ( TC) , triglyceride ( TG) and low density lipoprotein?cholesterol ( LDL?C) in serum among all groups ( P>0.05) . 3) Compared with the control group, the mRNA expression of 3?hydroxy?3?methylglutaryl coenzyme A reductase ( HMGCR) in liver of laying hens in 600, 900 and 1 200 mg/kg polysavone groups significantly de?creased (P<0.05), and the mRNA expression of cholesterol 7α?hydroxylase (CYP7A1) in liver of laying hens in 600 and 900 mg/kg polysavone groups significantly increased (P<0.05). There were no significant differences in the mRNA expression of sterol regulatory element?binding protein 2 ( SREBP?2) in liver and oc?cyte vitellogenesis receptor (OVR) in ovarian of laying hens among all groups (P>0.05). Our present study indicates that dietary supplemented with polysavone can reduce the whole egg and egg yolk cholesterol content. The possible mechanism of cholesterol lowering effects can result from reducing endogenous synthesis and more cholesterol excretion. The suitable dietary polysavone supplemented level of laying hens aged from 26 to 35 weeks is 900 mg/kg.