Serum Lipids of Young Show Racer and White Carneau Pigeons Fed a Semipurified Diet with or without Cholesterol

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Abstract
Six-weck-old Show Racer (SR) and White Carneau (WC) pigeons were fed a semipurified diet with or without cholesterol. The birds were autopsied after 0, 6, 12, 18, and 24 weeks of feeding. The aortas were examined and graded for atherosclerotic lesions. Serum concentrations of cholesterol, triglyceride, and phospholipid were determined. Aortic atherosclerotic lesions were observed only in WC fed the cholesterol-containing diet for 12 to 24 weeks. In contrast to earlier reports by others, significant differences in serum cholesterol, triglyceride, and phospholipid levels were observed between SR and WC fed basal diet without cholesterol. Such differences occurred only after 6 and/or 12 weeks of experimental feeding with the SR exhibiting lower levels of all three classes of lipids. Serum free, ester, and total cholesterol of both breeds were significantly elevated when cholesterol was added to the diet. When cholesterol-supplemented diet was fed to the SR, serum triglyceride concentrations were significantly elevated after 6, 12, and 24 weeks compared with those fed the basal diet while no such elevation was observed in the WC. When cholesterol-supplemented diet was fed to the SR, serum phospholipid concentrations were significantly elevated after 6, 18, and 24 weeks compared with those fed the basal diet while, for the WC, this occurred only after 6 weeks. Hypercholesteremia occurred among those WC which exhibited aortic lesions while those WC without lesions had much lower serum cholesterol levels. The aortas of the SR, even under hypercholesteremic condition, were normal. It could be concluded from this study that differences in lipid metabolism exist between these two breeds of pigeons. In these experiments hypercholesteremia proved to be a necessary but not sufficient pathogenic factor in atherogenesis. The additional “sufficient factor” in this context was the genetic background.