Effect of lactation on the distribution of mineral elements in goat milk

The distribution of mineral elements in milk is crucial for their absorption and utilization, however, there has been limited attention given to the status of mineral elements in goat milk. In this study, goat milk was collected at 4 lactation periods (1–3,90,150,240d) and separated into 4 fractions (fat, casein, whey, and aqueous phase). The concentrations of Mg, Ca, Na, K, Zn, Fe, Cu, Mn, Co, Ni, Mo, and Cr in 4 fractions were analyzed using an inductively coupled plasma emission spectrometer (ICP-OES). Our findings reveal that Ca, Zn, Fe, Cu, Mn, and Cr exhibit the highest levels in casein, while Mo demonstrates the highest content in whey. Additionally, Mg, Na, K, and Ni display the highest concentrations in the aqueous phase. Specifically, the contents of Ca, Cu and Fe in casein decrease from 1 to 3 d to 150 d of lactation but increase from 150 d to 240 d of lactation. Furthermore, the content of Mg in the aqueous phase decreases from 1 to 3 d to 90 d of lactation but increases from 90 d to 240 d of lactation. The content of Na and K in the aqueous phase decreases from 1 to 3 d to 150 d of lactation. Notably, the content of Mo in whey increases from 1 to 3 d to 150 d of lactation and decreases from 150 d to 240 d. Our research contributes to the advancement of understanding the bioavailability of mineral elements in goat milk.乳中矿物元素的分布对于其吸收与利用至关重要，然而目前针对山羊乳中矿物元素状态的研究关注较为有限。本研究采集了4个泌乳阶段（1~3日、90日、150日、240日泌乳期）的山羊乳样品，并将其分离为4个组分：脂肪、酪蛋白、乳清及水相。采用电感耦合等离子体发射光谱仪（inductively coupled plasma emission spectrometer, ICP-OES）对4个组分中的镁（Mg）、钙（Ca）、钠（Na）、钾（K）、锌（Zn）、铁（Fe）、铜（Cu）、锰（Mn）、钴（Co）、镍（Ni）、钼（Mo）及铬（Cr）的含量进行了测定。研究结果显示，钙（Ca）、锌（Zn）、铁（Fe）、铜（Cu）、锰（Mn）及铬（Cr）在酪蛋白组分中含量最高，而钼（Mo）在乳清组分中含量最高；此外，镁（Mg）、钠（Na）、钾（K）及镍（Ni）的最高含量均出现在水相组分中。具体而言，酪蛋白组分中的钙（Ca）、铜（Cu）及铁（Fe）含量从1~3日到150日泌乳期呈下降趋势，而在150日至240日泌乳期则呈上升趋势。此外，水相组分中的镁（Mg）含量从1~3日到90日泌乳期逐渐降低，90日至240日泌乳期则逐步升高。水相组分中的钠（Na）与钾（K）含量从1~3日到150日泌乳期持续下降。值得注意的是，乳清组分中的钼（Mo）含量从1~3日到150日泌乳期逐渐升高，150日至240日泌乳期则出现下降。本研究有助于深化对山羊乳中矿物元素生物利用度的认知。