International audienceAss's milk yield and chemical composition were investigated in two lactations at d 28, 45, 60, 75, 90, 105, 135 and 150 after parturition. Milk yield per milking (averaging 740 mL) of 6 asses of Martina Franca (n = 3) and Ragusana (n = 3) breeds, which quickly adapted to the milking machine procedures, increased in the second (or third) milking per day but was unaffected by stage of lactation or breed. Year of lactation, stage of lactation, breed and milking time did not influence the gross composition of the milk, except for fat and protein contents. The overall average protein percentage (1.72 g$\cdot$100 g$^{-1}$ of milk), showing a significant negative trend throughout lactation, was characterised by low casein (47.3% of crude protein) and whey protein contents (36.9% of crude protein). A specific whey protein profile was also found, being the relative percentage on total whey protein 4.48%, 6.18%, 29.85%, 21.03% and 22.56% for respectively lactoferrin, serum albumin, $\beta$-lactoglobulin, lysozyme and $\alpha$-lactoalbumin. The low average fat content of ass's milk (0.38 g$\cdot$100 g$^{-1}$ of milk), showing a high individual variability, was significantly affected by the year of the study; the lipid fraction was also characterised by high levels of linoleic (average 8.15 g$\cdot$100 g$^{-1}$ of total fatty acids) and linolenic acid (average 6.32 g$\cdot$100 g$^{-1}$ of total fatty acids). The ash content of ass's milk (0.39 g$\cdot$100 g$^{-1}$ of milk) was constant throughout the experimental period and showed high levels of Ca and P, the ratio of which, ranging between 0.93 and 2.37, was on average 1.48.Composition et caractéristiques du lait d'ânesse. La production et la composition chimique du lait d'ânesse ont été évaluées sur deux lactations successives à 28, 45, 60, 75, 90, 105, 135 et 150 jours après la mise bas. Au total, 6 ânesses de race Martina Franca (n = 3) et de race Ragusana (n = 3), rapidement adaptées à la traite mécanique, ont été utilisées. La production laitière par traite et par jour (en moyenne 740 mL) a été supérieure lors de la seconde (ou troisième) traite. Elle n'a été affectée ni par le stade de lactation ni par la race. L'année de lactation, le stade de lactation, la race et l'heure de traite n'ont pas influencé la composition brute du lait sauf ses teneurs en lipides et en protéines. Le pourcentage de protéines (moyenne de 1,72 g$\cdot$100 g$^{-1}$ de lait) a eu tendance à diminuer significativement tout au long de la lactation, et a été caractérisé par une teneur réduite en caséine (47,3 % des matières azotées) et en protéines sériques (36,9 % des matières azotées). Un profil particulier des protéines sériques a été mis en évidence, avec un pourcentage relatif par rapport aux protéines sériques totales de 4,48, 6,18, 29,85, 21,03 et 22,56 %, respectivement, pour la lactoferrine, la sérum albumine, la $\beta$-lactoglobuline, le lysozyme et l'$\alpha$-lactalbumine. La faible teneur du lait en matières grasses (0,38 g$\cdot$100 g$^{-1}$) a été caractérisée par une variabilité individuelle élevée. La fraction lipidique a présenté des niveaux élevés d'acide linoléique (moyenne de 8,15 g$\cdot$100 g$^{-1}$ d'acides gras totaux) et linolénique (moyenne de 6,32 g$\cdot$100 g$^{-1}$ d'acides gras totaux). Le contenu en cendres (0,39 g$\cdot$100 g$^{-1}$ de lait) n'a pas varié au cours de la période expérimentale et a été caractérisé par des valeurs élevées de Ca et de P, avec un rapport Ca/P compris entre 0,93 et 2,37 et une valeur moyenne de 1,48

Background: Vitamin D and calcium are important dietary compounds that affect bone mass, even if other minerals (potassium, zinc, etc.) and vitamins (A, C and K) are also involved. Vitamin D and certain minerals, in fact, play an important role in calcium homeostasis and calcium absorption. Hip fracture incidence is higher in Europe and the United States, where calcium is frequently included in the human diet; while the occurrence of these fractures is lower in developing countries, where diets are often poor in calcium. This condition is named the “calcium paradox”, and may be partially explained by phosphate toxicity, which can negatively affect mineral metabolism. It is important to maintain correct dietary calcium-phosphate balance in order to have a healthy life, reducing the risk of osteoporotic fractures in older people. Vitamin D can also act as a hormone; vitamin D2 (ergocalciferol) is derived from the UV-B radiation of ergosterol, the natural vitamin D precursor detected in plants, fungi, and invertebrates. Vitamin D3 (cholecalciferol) is synthesized by sunlight exposure from 7-dehydrocholesterol, a precursor of cholesterol that can also act as provitamin D3. Dietary intake of vitamin D3 is essential when the skin is exposed for short periods to ultraviolet B light (UV-B), a category of invisible light rays such as UV-A and UV-C. This can be considered the usual situation in northern latitudes during the winter season, or the typical lifestyle for older people and/or for people with very white delicate skin. The actual recommended daily intake of dietary vitamin D is strictly correlated with age, ranging from 5 μg for infants, children, teenagers, and adults—including pregnant and lactating women—to 15 μg for people over 65 years.

Donkey milk could be considered a good and safer alternative, compared to other types of milk, for infants affected by cow’s milk protein allergy, when breastfeeding is not possible. Interestingly, donkey milk has low allergenicity, mainly due to the low total casein amount, and the content of some whey proteins that act as bioactive peptides. The amount of lysozyme, an antibacterial agent, is 1.0 g/L, similar to human milk. Lactoferrin content is 0.08 g/L, with this protein being involved in the regulation of iron homoeostasis, anti-microbial and anti-viral functions, and protection against cancer development. Lactoperoxidase, another protein with antibacterial function, is present in donkey milk, but in very low quantities (0.11 mg/L). β-lactoglobulin content in donkey milk is 3.75 g/L—this protein is able to bind and transport several hydrophobic molecules. Donkey milk’s α-lactalbumin concentration is 1.8 g/L, very close to that of human milk. α-lactalbumin shows antiviral, antitumor, and anti-stress properties. Therefore, donkey milk can be considered as a set of nutraceuticals properties and a beverage suitable, not only for the growing infants, but for all ages, especially for convalescents and for the elderly.