Variability of Cholesterol Concentration in Plasma and Egg Yolks of Hens and Evaluation of the Effect of Some Dietary Oils

INTEREST in the metabolism of cholesterol in the laying hen has been greatly stimulated by the fact that the egg is one of the main sources of cholesterol for man. The relationship between plasma and egg yolk cholesterol has not been satisfactorily elucidated. Connor et al. (1965) demonstrated that the laying hen transfers cholesterol-4-C14 from the blood to the developing yolk. Popjak and Tietz (1953) showed that the chick ovary is able to synthesize cholesterol in vitro, but Andrews et al. (1968) concluded that ovarian synthesis accounted for only a very small part of the total cholesterol deposited in the egg. On the other hand, Dennis (1969) reported that cholestyramine had no influence on yolk cholesterol levels, although it significantly reduced the concentrations of plasma cholesterol, thus suggesting the possibility of pronounced cholesterol synthesis in the ovary. Considerable variation in blood cholesterol levels among hens of the same flock was…