Response to five generations of selection for blood cholesterol levels in White Leghorns.

The response to five generations of selection for high and low plasma cholesterol levels was examined in two lines of Single Comb White Leghorn chickens derived from the same population. An unselected control line was also maintained. Juvenile cholesterol levels of blood plasma were measured in 24,754 birds during the experiment. Males at 9 to 10 weeks of age had higher plasma cholesterol levels than females of the same age. Estimates of the heritability of plasma cholesterol level for males and females from the sire and dam components of variance in unselected population, ranged from .19 to .30. Realized heritabilities from the selected lines were lower and ranged from .14 to .19 with no significant differences between lines or sexes. Differences between the two selected lines in the fifth generation were 37 mg% for males and 33 mg % for females. High cholesterol levels were associated with high mortality. The estimated genetic correlation between plasma cholesterol and egg production was negative. After five generations of selection for plasma cholesterol, yolk cholesterol was 108 mg % lower in the low selected line than in the controls, but there was little difference between the high selected line and controls in this trait.