Further studies on lipotropism in the domestic duck (White Pekin).

Abstract

On choline-free diets containing 10, 18, and 28% casein, the total liver lipids of ducklings were found to be 34.8, 25.0, and 13.8% respectively. Supplementation of the 10% casein diet with 0.5% methionine increased the liver lipids. The same amino acid has no effect at the intermediate level of casein while it is lipotropic at the 28% casein level. In similar experiments with a purified soybean protein (low in methionine) fed at levels of 12, 21.7, and 27.9%, the liver lipids were 31.8, 26.6, and 27.6% respectively. These values do not differ significantly from each other. Methionine was found to be lipotropic at any of these three levels of soybean protein, and more so as the level of the soybean protein increased in the diet. From these results, it is concluded that the purified soybean protein used is a nonlipotropic protein, while casein is definitely lipotropic in ducklings. The lipotropic activity of methionine is closely related to the quality and quantity of the protein in the diet. On high fat diets containing 22, 32, and 42% fat, choline had no lipotropic effect. The average liver lipids for all groups ranged from 11 to 15%. High fat diets are less inducive of fatty livers than high carbohydrate diets. Ducklings fed a fat-free, choline-free basal diet presented livers with an average total lipids of 18%. Supplementing the basal diet with 1% cholesterol increased the liver lipids to 22%. Inositol is lipotropic either in the presence or absence of cholesterol, but choline was much more effective under similar conditions. The two lipotropic factors have a synergistic action and the reduction of the liver lipids is primarily on the glyceride fraction. Cholesteryl ester was at its lowest value in the group fed the basal diet supplemented with inositol only.