Mare’s Milk as a Natural Probiotic-Antimicrobial Ecosystem: Composition, Microbial Ecology, and Functional Implications

Mare’s milk has been increasingly recognized as a distinctive non-ruminant dairy matrix with intrinsic functional properties linked to its biochemical composition and spontaneous fermentation ecology. Compared with ruminant milk, mare’s milk is characterized by high lactose availability, a whey-dominant protein fraction, low casein content, and the presence of host derived antimicrobial proteins such as lysozyme and lactoferrin. This article presents a narrative integrative review that synthesizes peer reviewed evidence on mare’s milk as an intrinsically organized probiotic antimicrobial system by integrating milk composition, microbial architecture during spontaneous fermentation, and multilayered antimicrobial defense mechanisms. Particular emphasis is placed on Sumbawa mare’s milk as a tropical, low input traditional production system that provides a comparative model to classical Central Asian koumiss fermentation. Across diverse studies, lactic acid bacteria (LAB) are frequently reported as dominant microbial groups, supported by ecological selection pressures imposed by the milk matrix and reinforced by LAB mediated fermentation metabolites. Antimicrobial functionality is shown to arise from the combined action of host derived proteins, LAB produced organic acids and bacteriocins, and auxiliary bioactive components rather than from isolated factors alone. However, most available evidence is derived from in vitro assays, culture-based studies, and observational analyses, highlighting important limitations in clinical and in vivo validation. By integrating fragmented findings into a system level framework, this review identifies key conceptual linkages, methodological constraints, and future research priorities relevant to food safety, non-thermal processing, and clean-label functional dairy innovation.