Composition, physiochemical properties, nitrogen fraction distribution, and amino acid profile of donkey milk.

This research investigated the chemical composition, nitrogen distribution, and amino acid profile of donkey milk from a specific breed in China. The results indicate that the milk’s composition is closer to that of mare and human milk rather than other mammals, with certain variations observed during lactation.

Chemical Composition

• The study analyzed milk samples from the Jiangyue breed of donkeys in Northwest China, focusing on their chemical composition during lactation.
• On average, donkey milk was found to contain 9.53% total solids, 1.57% protein, 1.16% fat, 6.33% lactose, and 0.4% ash. Hence, this closely resembles the composition of mare’s and human’s milk than that of other mammals.

Physiochemical Properties

• Throughout the lactation period studied, the pH and density of the milk remained constant.
• The protein and ash content showed a noticeable decrease, with lactose content increasing during the first 120 days postpartum, before experiencing a fall.
• The fat content demonstrated a wide range of variability.

Nitrogen Fraction Distribution and Amino Acid Profile

• The study observed only minor changes in the content and percentage of casein, whey protein, and amino acids (AA).
• It was revealed that the ratio of casein to whey protein in donkey milk (52:37) was between the lower ratio found in human milk and the higher ratio found in cow milk.
• Furthermore, analysis using Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) showed that donkey milk is rich in beta-lactoglobulin and lysozyme.
• The essential amino acids present in donkey milk constituted 38.2% of its protein content, higher than the percentages found in mare and cow milk.
• Specifically, donkey milk had higher levels of serine (6.2%), glutamic acid (22.8%), arginine (4.6%), and valine (6.5%) and a lower level of cystine (0.4%) when compared to mare and cow milk.