Changes in Egg Composition of Lines Selected for Divergence in Yolk Cholesterol Concentration

Abstract

The changes in the proportions of the egg, percentage yolk dry matter, and percentage yolk fat as a response to selection pressure for divergence in yolk cholesterol concentration of the Cornell randombred Leghorn (LC) and the Athens-Canadian randombred (AC) population were determined. Differences were observed between the two populations and in the high and low cholesterol lines within populations.The egg weight of the LC population was significantly greater and the yolk weight less than that of the (AC) population, resulting in a significantly lower percent yolk in the LC population. Yolk dry matter of the LC population was slightly, but significantly, lower than that of the AC population.Both egg and yolk weights of the high cholesterol lines in both populations were significantly greater than that of the low lines. The differences were not proportional; percent yolk of the high cholesterol line was significantly lower than that of the low line. The percent dry matter of the high cholesterol line in the AC, but not in the Leghorn population, was significantly higher than that of the low line. These differences did not appear to be a response to the selection pressure for divergence of yolk cholesterol concentration. When total cholesterol mass was calculated on the basis of total amount in the yolk or gram of dry matter, the divergence between the high and low lines was similar to that when expressed as milligrams cholesterol per gram whole yolk. Correlations between yolk cholesterol concentration and other egg traits were low.