Date of Award

1984

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

A series of seven short term experiments were conducted using SCWL laying hens to study liver and egg yolk cholesterol changes caused by dietary lipids. For all the experiments, the individually caged layers were 55 week-old or older and automated procedures were used to measure the liver and yolk cholesterol responses. In the first four experiments the diets contained olive or safflower oils at 8%, oleic or linoleic acids at 6%, all with or without cholesterol. In experiment 5, dietary levels of olive and safflower (1 and 8%) and cholesterol (0 and 1%) were factorially combined and examined. The olive and safflower oils at dietary levels of 1, 5 and 9% each were also examined in separated experiments in factorial combinations with cholesterol at levels of 0, .5 and 1%. The addition of cholesterol to the oil of fatty acid diets resulted in significant (P < .05) elevations of yolk cholesterol levels. The responses of liver and egg yolk cholesterol contents to dietary olive oil were positive and linear. As dietary cholesterol was increased the liver cholesterol content increased in a quadratic fashion with the rate of increase higher after the second level (.5%) of dietary cholesterol. As dietary cholesterol was increased the egg yolk cholesterol content increased in a quadratic fashion with the rate of increase higher after the second level (.5%) of dietary cholesterol for safflower oil whereas the rate decreased with olive oil. A significant (P < .05) positive olive oil by cholesterol interaction was detected for liver cholesterol whereas the same interaction for daily feed intake showed a significant negative response (P < .05). The significant (P < .05) olive oil by safflower oil by cholesterol interaction for feed intake further corrolsorated the olive oil by cholesterol for the same variable, indicating that feed consumption is a control mechanism for reducing exogenous cholesterol overload. It was concluded that the oleic acid contained in olive oil was the main nutritional factor determining the significant changes of the liver and egg yolk cholesterol.

Pages

129

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