Donkey milk has received increasing attention in recent years due to its unique nutritional composition and potential biological activities. This comprehensive review analyzed the main nutritional components of donkey milk, including proteins, lipids, carbohydrates, vitamins, and minerals, while also examining its significant biological activities such as antioxidant, antimicrobial, immunomodulatory, and anti-inflammatory properties. The protein profile of donkey milk is notable for its high proportion of whey proteins (55–65%), resembling human milk more closely than cow milk. Its relatively low-fat content (approximately 1.29%) with higher proportions of unsaturated fatty acids provides nutritional advantages for specific dietary needs. The carbohydrate content, primarily lactose, contributes to energy provision and calcium absorption. Donkey milk is also distinguished by its rich vitamin profile, particularly vitamin C (about 4.75 times higher than cow milk), and essential minerals including calcium, phosphorus, and zinc. The biological activities of donkey milk extend to various applications in infant nutrition, particularly for children with cow milk protein allergies, potential medical treatments for infections and inflammatory conditions, and cosmetic formulations. Despite these promising attributes, the donkey milk industry faces challenges including low milk yield, lack of standardized production methods, and quality control measures. The sustainable development of the donkey milk industry requires comprehensive approaches to resource protection, technological innovation, brand building, and supportive policies to realize its full potential in contributing to human health and economic development.

Locally sourced roughages constitute the dietary foundation of donkey production in northern China, yet their fermentation behavior in the donkey hindgut remains poorly characterized. The present study employed in vitro batch cultures to compare the dry matter disappearance (IVDMD), gas production (GP) kinetics and short-chain volatile fatty acid (VFA) profiles of five locally available feedstuffs—peanut vine (PNV), soybean straw (SBS), wheat shell (WS), reed grass (RG) and bamboo leaf (BL)—when incubated separately with cecal or colonic microbial inocula obtained from Dezhou donkeys. After 40 h incubation, both IVDMD and total VFA concentrations ranked identically across the two hindgut segments: PNV > SBS > WS > RG > BL (p < 0.05), and all indices were consistently higher in the cecal than in the colonic fermentation system (p < 0.05). The asymptotic gas production (A) and the time required to reach half of A (T₁/₂) followed the same ranking as IVDMD (p < 0.01), indicating that feedstuffs with greater fermentable substrate availability sustained fermentation for longer periods. In contrast, the fractional gas production rate (c) and the average gas production rate (AGPR) in RG and BL exceeded those of PNV, SBS, and WS under cecal incubation (p < 0.05), reflecting rapid utilization of a small pool of readily fermentable components in these fibrous substrates. Regarding VFA stoichiometry, BL yielded the highest molar proportion of acetate and PNV the lowest in the colonic system (p < 0.05), whereas the propionate proportion followed the order PNV > SBS > WS > RG > BL (p < 0.01). Consequently, the acetate-to-propionate (A:P) ratio and the non-glucogenic-to-glucogenic (NGR) ratio were highest in BL (p < 0.05). The molar proportions of butyrate and branched-chain VFAs (BCVFAs) in WS, RG, and BL were greater than those in PNV (p < 0.05). Collectively, the five feedstuffs differed markedly in their fermentability, kinetic behavior, and VFA yield profiles, reflecting distinct energy-supply potentials for the donkey host. PNV and SBS exhibited superior overall in vitro fermentation performance and are therefore recommended as preferred roughage sources, whereas BL and RG may serve complementary roles by supporting hindgut epithelial health through elevated butyrate production. These findings provide a mechanistic basis for the rational selection and combination of locally sourced roughages to optimize feeding strategies and improve feed-use efficiency in donkey production.