Donkey milk: from stable to cradle

The donkey population in Europe had been experiencing a decline over the past twenty years, due to the growing automation in agriculture, and to the depopulation of rural districts. However, the European donkey population is now increasing, thanks to the interest in donkey's milk (DM). Donkeys as a dairy species have been known since ancient times, also for DM beneficial properties in skin care. In the late nineteenth century, DM was successfully used for feeding orphan infants in Paris (Salimei, 2012). More recently, donkey's milk has been receiving a growing interest as food for sensitive consumers, such as children with cow's milk protein allergy and preterm infants. Clinical studies have indicated that DM can be successfully used as an alternative to the available hypoallergenic formulas for infants suffering from cow milk protein allergy and as a human milk supplement for preterm infants. DM has been shown to be well tolerated in 80-92% of children allergic to cow milk (Monti et al.,2007, Monti et al., 2012, Barni et al. 2018). In preterm infants, the fortification of human milk with DM instead of cow milk, led to a significant improvement of the episodes of feeding intolerance during their stay in the Neonatal Intensive Care Unit (Coscia et al., 2018). The biochemical basis for the DM nutritional adequacy in infants and children is discussed. DM protein and lipid fractions show a substantial similarity to that of human milk (Bertino et al., 2011). DM has a total protein content which is more similar to human milk than cow milk. The comparative analysis of human, donkey and cow milk proteome has revealed that the also protein profile is more similar among human and DM. DM is characterized by a low casein content, with values very close to that found in human milk (Polidori et al., 2015). The major cow milk allergens are either absent, present in traces or they are very different in term of aminoacid sequence in DM. The fat content of DM is lower than the fat content of human milk and this difference is associated with low energy content, thus representing a main limitation to its use as a nutritional source for children who are allergic to cow milk protein during the first year of their life. However, the lipid fraction of DM has shown a more favourable fatty acid composition than that of the milk fat of ruminants, because it is richer in polyunsaturated FA (PUFA). Fat in DM has shown a higher concentration of C18:3n-3 and n-3 FA, and a lower saturated FA (SFA) content than cow milk, as well as a lower n-6 to n-3 FA ratio (Gastaldi et al., 2011).