Nutritional value and the content of minerals in eggs produced in large-scale, courtyard and organic systems

The aim of this study was to determine the content of basic nutrients as well as selected macroand micro-elements in the albumen and yolk of eggs produced at large-scale, commercial poultry production farms (10) as well as in organic (8) and courtyard farms (12). Ten eggs were randomly collected 3 times on each farm. For chemical analyses, the eggs were hard-boiled for 15 min and then stored at a temp. of 4°C until analyzed. The albumen and yolk of hard-boiled eggs were assessed for the content of dry matter, total protein, crude fat and crude ash, and for their energy value (net Atwater equivalents) as well as the concentrations of K, Na, Ca, Mg, P, Fe, Zn, Cu, Se and Mn. No differences were observed in the content of dry matter, total protein and crude ash. However, differences were demonstrated for the crude fat content, the highest (P < 0.05) level of which was found in eggs from the organic system (higher by 60% in albumen and by 17% in yolk than in the other eggs), which was accompanied by an increased energy value of these eggs. In all the analyzed eggs, similar concentrations were noted for Mg (egg white) and P (egg albumen and yolk). The albumen of eggs from the organic system was characterized by the highest (P < 0.05) content of K, Na, Ca, Zn, Se and Mn. In turn, the albumen of eggs from large-scale commercial poultry production farms contained the highest (P < 0.05) levels of Fe, Cu and Se. Yolks of the eggs from the organic system accumulated the highest (P < 0.05) levels of K, Na, Ca, Mg and Fe. In turn, the highest (P < 0.05) concentrations of Zn, Se and Mn were determined in yolks of the eggs produced in the homestead system, and that of Cu – in yolks of the eggs from large-scale commercial production. A highly positive correlation between concentrations of minerals in the albumen and yolk of the analyzed eggs was reported for the following pairs: K-Na, Se (0.998, 0.93); Na-Na (0.949); Ca-Mg, Mn (0.994, 0.951); Mg-Ca, Mn (0.986, 0.982); P-Ca, Mn (0.997, 0.961); Fe-K, Mg, P, Zn (0.999, 0.937, 0.988, 0.999); Zn-Ca, Mn (0.999, 0.945); Se-Cu (0.971) and Mn-Ca (0.902), whereas a negative correlation for: Ca-Fe, Cu (-0.974, -0.994); Mg-Cu (-0.921); P-Fe (-0.933); Zn-Fe (-0.912); Cu-Na (-0.951); Se-K, P, Zn (-0.960, -0.910, -0.962) and Mn-Se (-0.979)