Widely targeted metabolomics reveals dynamic alterations in colostrum, transitional, and mature milk of jennies

Donkey milk has recently garnered significant attention as a source of nutrition and potential health benefits for humans. However, a thorough understanding of the metabolite profile of colostrum and milk of jennies during the first two weeks post-foaling is still lacking. Herein we employed widely targeted metabolomics to comprehensively characterize the metabolite profiles of colostrum, transitional, and mature milk of jennies (n = 18) at four different timepoints after foaling: day 1 (colostrum; L1), day 3 (early transitional milk; L3), day 7 (late transitional milk; L7), and day 14 (mature milk; L14). Overall, 606 metabolites across 17 classes and 304 significantly different metabolites were identified. In comparison with mature milk, colostrum exhibited a higher abundance of lipids, including fatty acids, glycerophospholipids, and sphingolipids. Transitional milk, on the other hand, was characterized by a significant increase in the levels of amino acids and their metabolites and organic acids and their derivatives, which participate in various protein biosynthesis and absorption-related metabolic pathways essential for neonatal development. Altogether, our data provide comprehensive insights into how the stage of lactation affects the metabolism of bioactive components in donkey milk. This information enhances our understanding of how to optimize milk production in jennies.