Dietary levels of methionine plus cystine and chelated copper on the chemical composition of eggs and yolk cholesterol of 49-week-old brown laying hens

The present study aims to evaluate the possible interactions of dietary levels of methionine plus cystine (Met + Cys) and organic copper (Cu) on the chemical composition of eggs, using 320 Hy-Line Brown hens at 49 weeks of age. Composition and deposition variables were evaluated in a 4 × 5 factorial arrangement, with total analysed levels of 18, 44, 71, and 99 mg kg-1 of Cu and 0.613, 0.631, 0.816, 0.918, and 0.955% Met + Cys. We allocated four replicate cages (four hens/cage) to each treatment group. Two eggs per plot were sampled to determine the chemical composition of albumen and yolk, based on natural and dry matter and on daily rates of deposition. An interaction effect of Met + Cys and Cu levels was observed for deposition rates of ash and Cu in the yolk, and the chemical composition of Ethereal Extract (EE) and ash in eggs, EE in albumen and Nitrogen, EE, and ash in the yolk. An isolated effect was observed for Met + Cys on egg chemical composition and on shell and yolk fractions, as well as on deposition rates of albumen N, EE, and ash, and yolk EE. The yolk cholesterol content increased by 18.17% with increasing Met + Cys in diets. In conclusion, the chemical composition of eggs varied with dietary Met + Cys and organic Cu concentrations. Dietary levels of Met + Cys determined the yolk cholesterol concentration in laying hens.