Divergent effects of excess dietary vitamin A on alimentary cholesterolemia in cockerels of different genetic backgrounds.

The variable effect of excessive vitamin A intake on alimentary cholesterolemia was investigated in cockerels of strains of White Leghorns and New Hampshires. With the New Hampshire cockerels, the feeding of 0.5% of dietary cholesterol resulted in greater cholesterolemia when the diet contained 1700 I.U. of vitamin A per kilogram than when it contained 22000 I.U. of vitamin A per kilogram. With the White Leghorn cockerels, on the other hand, cholesterolemia was enhanced with the higher level of dietary vitamin A. Absorption of a single oral dose of cholesterol was increased in birds of both breeds when vitamin A had been given previously by injection. In the White Leghorn cockerels the percentage of newly absorbed cholesterol in the hepatic pool was reduced by vitamin A administration, whereas in the New Hampshire cockerels the percentage was increased. It was concluded that excess vitamin A may have divergent effects on alimentary cholesterolemia in chickens of different genetic backgrounds as a result of opposite effects on the liver-blood ratio of a large load of cholesterol.