| CLA was Studied at home and abroad by scholars as a natural additive functional application of great potential, but there're not exactly the same results.So We need for more Research in the actual livestock and poultry production. The test for local conditions ,We selected typical local chicken breeds in China——Gushi chicken for the trial.We Studied the influence of Gushi chicken production performance, egg quality, composition of egg yolk and egg yolk cholesterol by CLA diet. We was Studied the mechanism of CLA through nutrition, molecular biology. As for the CLA to promote the use of new additives and animal nutrition and the relationship between gene interaction and provide a theoretical basis.In order to study the influence of conjugated linoleic acid on the effects of egg-yolk cholesterol and its role in the mechanism to Gushi chicken, this study mainly from the following two aspects of research.Test1. The influence of conjugated linoleic acid on egg quality and serum biochemical indexes to Gushi chicken.Two hundred and eighty- eight 30-week-old Gushi hens were randomly distributed into four groups of seventy-two hens each and maintained in individual laying cages, throughout 6 weeks of the experiment. They were assigned to the four treat-menu that consisted of commercial layer diets containing 0, 5, 10,or 20 g pure CLA/kg. The test results show that: Adding dietary CLA can reduce Gushi chicken feed intake, when its adding 0.5%, the egg production rate was a slight increase than the control group there in CLA when added up to 2%, laying rate lower than the control group 0.05 percentage points to reach a significant level of difference. CLA diet can improve the egg weight, as a result of dietary CLA in reducing the rate of Gushi chicken laying eggs at the same time increased the weight so that it did not affect the ratio of Feed and egg weight.The TC and TG were significantly reduced with the added amount of conjugated linoleic acid in egg yolk(P <0.05), but it will not be affected that egg shape index and the Harrington unit,and when the CLA to add the amount of conjugated linoleic acid reach 2%, it can significantly improve weight and color of egg yolk(P <0.05). The TC and VLDL-C had increased at the first and then decreased trend as conjugated linoleic acid to add volume, reaching a significant difference (P<0.05).Dietary CLA can add a significant increase in saturated fatty acids and polyunsaturated fatty acid content in egg-yolk of Gushi chicken, and with the addition of CLA to increase their content in the egg yolk in the rising trend. The mono-unsaturated fatty acids diminished with CLA to increase in the egg yolk. Egg yolk deposition of CLA, with the addition of CLA diet increased significantly increase.CLA diet in addition to the depth of color of egg yolk, but it have adversely affected on the egg smell, taste and flavor, so that egg yolk had a smell, an increase hardness of egg yolk, thus reducing taste of egg that Gushi hens, and impact of the egg quality. The triglyceride (TG), total cholesterol (TC), high density lipoprotein (HDL-C), low density lipoprotein (LDL-C) and very low density lipoprotein (VLDL-C ) added to the trend of increasing and then decreasing with the content to increase the amount of CLA ,it will reached maximum when the amount of CLA to add content to 0.5%, and then add the amount along with the increase of CLA significantly reduced. This have the Similar trend with the egg yolk content of TC and TG.Test2. The effects to OVR and APO-Ⅱgene expression of Gushi chicken by Conjugated linoleic acidIn order to study the effects of cholesterol deposition on CLA by the molecular mechanism ,in the test 1 carried out to the forty-fifth day, Each group randomly selected 6 chicken, Liver and ovarian tissue collected 1 to 2 grams . Collected a total of 24 liver tissue and 24 ovarian tissue samples,for total RNA extraction. Selection the apolipoprotein -Ⅱgene (APO-Ⅱ) and the vitellogenin receptor gene (OVR) as a target gene that they are closely related to egg-yolk cholesterol transport and deposition, using FQ- PCR for the identification of differentially expressed genes.The results showed that:The CLA significantly reduced the OVR gene expression that Gushi chicken liver and ovarian tissue (P <0.01), but different levels of CLA addition on gene expression in OVR of ovarian does not significantly affect (P > 0.05), the expression of liver OVR with significant differences (P <0.05). Dietary CLA did not affect on the APO-Ⅱgene expression that. APO-Ⅱis the crucial factors that cholesterol transport to egg yolk, but it can not reduce the APO-Ⅱgene expression of Gushi chicken by adding CLA to dietary.If we want to control the Cholesterol content of egg by reduce the APO-Ⅱgene expression ,We need to further explore other methods.The mechanism may be it can inhibit the HMG-CoA reductase activity that the dietary CLA that impact of OVR gene expression to Gushi chicken, thus affecting the content of cholesterol in serum and egg yolk, thereby affecting plasma yolk precursor levels, and affect gene OVR expression.It from the VLDL and VTG that liver mainly to the synthesis of yolk precursors that cholesterol of egg yolk, which depends mainly on VLDL to enter the number of oocytes, OVR as VLDL receptor gene, its role should not be underestimated.It accumulated in the egg yolk that material of yolk by OVR genes, and also decided that the size and weight of egg, and affecting the rate of Gushi chicken. |
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