Effect of Azasterols on Sterol Metabolism in the Laying Hen

Two azasterol compounds, 20,25-diazacholesterol and U-22,593A (Upjohn Co.) were fed to laying hens and were found to increase egg cholesterol concentration when measured with Pearson’s method at 550 mμ., but reduced cholesterol concentrations were found with this method when measurements were made at 625 mμ. This discrepancy was found to be due to the reaction of sterols other than cholesterol with the reagent used for spectrophotometric analysis in the method. Thin layer chromatography and gas-liquid chromatography revealed that blood and egg yolk from the drug treated hens contained desmosterol, cholesterol, and traces of unidentified sterols while blood and egg yolk from untreated controls contain only cholesterol. Additional experiments with these drugs has shown that desmosterol accumulates in blood and egg yolk at the expense of cholesterol, hence true cholesterol content of eggs from drug treated hens is reduced but it is replaced by another sterol. Levels of 20,25-diazacholestetol and U-22,593A of 1.0 mg./kg. diet or more also reduce egg production and egg size, perhaps by interference with estrogen synthesis from cholesterol. At low levels of drug feeding, egg production is normal but a shift in sterol pattern of the egg yolk is noted. The results indicate that sterol composition of eggs can be altered without interference with reproductive performance.