Effect of varying legume proportions in the hen diet on selected element content in eggs [pdf]

Background.Egg mineral composition can be influenced by several factors, including the genotype, age, housing system, and nutrition of laying hens.The modification of egg elemental composition by dietary supplementation is widely studied; however, the effect of dietary protein sources on the element profile remains insufficiently explored, even though these sources strongly influence nutrient availability.This study was conducted to determine whether replacing soybean meal with blue lupine (Lupinus angustifolius) in laying hen diets affects the content of selected elements in egg yolk and albumen.Material and methods.The feeding experiment involved 360 Hy-Line Brown laying hens assigned to six dietary treatments.The diets differed in the proportions of soybean meal and blue lupine, ranging from 15.43% soybean meal with no lupine to a complete replacement of soybean meal with 25% lupine.After a four-week feeding period, egg yolks and albumen were collected, homogenized, lyophilized, and subjected to microwave-assisted acid digestion.The contents of selected macroelements, trace elements, and toxic elements were determined using inductively coupled plasma mass spectrometry.The results were analysed using one-way ANOVA followed by Tukey's test, and Pearson's correlation coefficients were calculated.Results.Dietary modification significantly affected the mineral profile of eggs, with clear differences between yolk and albumen.The yolk showed a greater ability to accumulate macro-and trace elements, particularly phosphorus, calcium, iron, zinc, and selenium.Moderate lupine inclusion, especially at 15-20%, favoured the deposition of selected essential elements, whereas complete soybean meal replacement with 25% lupine tended to disturb mineral balance.Selenium was the element most clearly associated with its dietary level, showing significant positive correlations between feed and both egg fractions.Egg albumen had a more stable mineral profile and was less responsive to dietary changes.Toxic elements were detected at low levels, and their accumulation appeared to be influenced by multiple factors rather than direct feed-to-egg transfer alone. Conclusion.The findings indicate that the mineral composition is influenced not only by dietary intake of the elements; under controlled conditions, it was shown that changing the dietary protein sources in the nutrition of laying hens can impact the elemental content of eggs, even without targeted mineral supplementation.Moderate replacement of soybean meal with blue lupine may support the deposition of selected essential elements in yolk, even if no significantly higher supply of these elements was found in the diet.However, consumers should interpret the implications of these changes for nutritional value with caution, as statistically significant differences do not necessarily indicate meaningful improvements in dietary mineral intake.The results also highlight the need for further studies on mineral bioavailability, long-term feeding effects, and the monitoring of toxic element transfer associated with varying proportions of soybean meal and blue lupine in laying hen diets.