Variations in the Mineral Profiles of the Micellar and Water-Soluble Fractions of Goat Milk between the First and Second Lactations

Abstract

The objective of this study was to determine the variations in the mineral profile of the micellar and water-soluble fractions of goat milk between the first and second lactations. Twenty Saanen dairy goats in their first (n=10) or second lactation (n=10) were randomly selected for this trial. Milk samples were obtained monthly from all the animals for seven months. The concentrations of sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), phosphorous (P), iron (Fe), copper (Cu), zinc (Zn), selenium (Se), nickel (Ni), cadmium (Cd), and arsenic (As) in both the water-soluble and micellar fractions were analyzed. Na, Mg, Zn, K, and As were positively correlated with both total milk production and lactation days in the first-lactation dairy goats (r>0.9; p<0.05). For the second-lactation goats, Ca, Se, and P had negative correlation coefficients with days in lactation (r<-0.75; p<0.05). Overall, the mineral contents in the micellar and water-soluble fractions of first- and second-lactation goats varied throughout lactation. The concentrations of essential elements in the milk of goats from the first and second births did not significantly differ. The distribution of essential and toxic minerals in the micellar and aqueous fractions found in goat milk is important for identifying the fraction with the highest percentage of recorded concentration of a particular mineral, especially toxic ones. For example, the content of arsenic in goat milk was above the international standard allowed for drinking water (10 µg L^-1), which is important for monitoring the quality and safety of goat milk.