Content of macro- and microelements in goat milk in relation to the lactation stage and region of production

The content of macro- and microelements in milk depends on a variety of environmental, genetic and physiological factors. The aim of the study was to determine the effect of the region of production and stage of lactation, associated with the production season, on the content of selected macro- and microelements, including potentially toxic elements, in goat milk. The material consisted of goat milk samples collected from farms in two regions of Poland: 74 samples from central-eastern Poland (the Provinces of Lublin and Świętokrzyskie) and 149 from southern Poland (the Bieszczady mountains). The milk was collected in three seasons: winter (75 samples), summer (111) and autumn-winter (37). In each milk sample, the percentage of casein, protein, fat, lactose and dry matter was determined, as well as the concentrations of K, Ca, Na, Mg, Zn, Fe, Cu and Mn. K, Ca, Na, Mg and Zn using a Varian 240FS AA spectrometer, by the flame atomic absorption technique, while Fe, Cu and Mn were determined in a graphite furnace with the Zeeman background correction, using a Varian 240Z AA spectrometer. The goats’ production peak was in the summer, when they were at pasture. From mid-lactation they produced milk with significantly (p ≤ 0.01) higher concentration of components. Milk obtained in stage I of lactation (winter feeding) was the richest source of Zn, Fe and Cu, while stage II milk (summer feeding) had the highest K content, and stage III milk (autumn-winter feeding) had the highest content of Ca, Na, Mg and Mn. Concentration of Zn, Fe and Cu decreased over the course of lactation. Milk obtained in the Bieszczady mountain region had significantly (p ≤ 0.01) higher content of dry matter, fat and protein. It also contained significantly (p ≤ 0.01) more Ca, Na, and Mg, and less K and Zn in comparison with the milk of the goats raised in central-eastern Poland. The highest positive correlation coefficients were noted between the content of Ca and Mg, Zn and Fe, Zn and Cu, Na and Mg, and Fe and Cu, while K content was negatively correlated with that of Na, Ca and Mg (p ≤ 0,001).