Effects of tryptophan supplementation to a maize-based diet on lipid metabolism in laying hens.

1. Experiments were conducted with laying hens to determine the effects of supplementing 0, 1.0, 2.0 and 3.0 or 4.0 g trp/kg diet to a maize and soyabean meal-based laying ration (basal tryptophan = 1.66 g/kg) on tissue lipid concentrations. 2. Plasma cholesterol, triglycerides and nonesterified fatty acids were increased by supplementing the diet with 1.0 g trp/kg diet and decreased with 3.0 or 4.0 g trp/kg diet. A significant quadratic effect of supplemental tryptophan was observed on plasma lipids in most cases. The observed effects diminished with time. No consistent changes were observed in plasma glucose concentrations. 3. Total liver lipids were reduced by supplemental tryptophan at all concentrations.