The research on factors influencing on cholesterol synthesis in chickens and egg cholesterol contents

鸡蛋含有相对较高的胆固醇含量。对于蛋生产者来说，能够提供低胆固醇蛋在经济上是有利的，并且许多研究努力已经指向这个目标。肝脏是产蛋鸡胆固醇生物合成的主要部位。然而，肠粘膜已被证明是仅次于肝脏的内源性合成胆固醇的来源。本研究旨在研究不同类型的膳食脂肪对胆固醇生物合成的影响，通过HMG-CoA还原酶活性在肠粘膜，以及生长鸡的肝脏（实验1和2）。此外，将产蛋鸡与非产蛋鸡的这种酶活性进行比较（实验3）。试验1中，肝脏HMG-CoA还原酶的活性以饲喂含牛脂日粮的雏鸡最高。喂食含红花或椰子油的饲料的鸡与喂食含橄榄油的饲料的鸡相比，肠道HMG-CoA还原酶活性显着降低。在实验2中，肝脏HMG-CoA还原酶活性显着较高时，无脂肪和三月桂酸甘油酯喂养比任何其他甘油三酯喂养。该活性在饲喂含三硬脂酸甘油酯的饲料的雏鸡中显示出最低值。空肠和回肠中的HMG-CoA还原酶活性在饲喂三月桂酸甘油酯时显著或倾向于高于饲喂任何其他甘油三酯时。除了喂食三月桂酸甘油酯时，饮食中饱和脂肪的存在对肠道HMG-CoA还原酶活性没有显著影响，这与向饮食中添加高度不饱和脂肪时所显示的效果不同。肝、肠HMG-CoA还原酶活性与肠上皮细胞HMG-CoA还原酶活性及胆固醇含量之间无显著相关性。试验3中，蛋鸡肝脏HMG-CoA还原酶活性显著高于对照组，

Egg contains a relatively high cholesterol content. It would be economically advantageous for egg producer to be able to provide a low cholesterol egg and many research efforts have been directed toward this goal. The liver is the primary sites of cholesterol biosynthesis in laying hens. However, intestinal mucosa has been demonstrated to be second only to liver as a source of endogenously synthesized cholesterol. The present investigation was designed to study the effect of different type of dietary fats on cholesterol biosynthesis through HMG-CoA reductase activity in the intestinal mucosa, as well as the liver of growing chicks (Experiment 1 and 2). Furthermore, this enzyme activity was compared laying with non-laying hens (Experiment 3). In experment 1, the hepatic HMG-CoA reductase activity showed the highest value in chicks fed the tallow-containing diet. Chicks fed diets containing safflower or coconut oil resulted in a significantly lower intestinal HMG-CoA reductase activity in comparison with those fed the olive oil-containing diet. In experiment 2, the hepatic HMG-CoA reductase activity was significantly higher when fat-free and trilaurin were fed than when any other triglycerides were fed. This activity showed the lowest value in the chicks fed the diet containing tristearin. The HMG-CoA reductase activities in the jejunum and ileum were significantly or tended to be higher when trilaurin was fed than when any other triglycerides were fed. Except when trilaurin was fed, the presence of saturated fat in the diet did not have a significant effect on the intestinal HMG-CoA reductase activity, unlike the effect shown when a highly unsaturated fat was added to the diet. There was no significant correlation between the HMG-CoA reductase activities of the liver and intestine, and this enzyme activity and cholesterol content of intestinal epithelial cells. In Experiment 3, the hepatic HMG-CoA reductase activity in laying hens was significantly higher than those