Donkey milk has several important compositional similarities to human milk. It is characterized by relatively low fat and protein concentrations, high lactose content, a high proportion of whey proteins, and the presence of bioactive proteins such as lysozyme and lactoferrin. These characteristics have made donkey milk a subject of research in food science, nutrition and the study of milk-protein allergy.
1. Average Composition of Donkey Milk
| Component | Typical Amount per 100 mL |
|---|---|
| Water | Approximately 89–91 g |
| Total solids | Approximately 9–11 g |
| Fat | Approximately 0.5–1.5 g |
| Protein | Approximately 1.3–2.0 g |
| Lactose | Approximately 6.0–7.0 g |
| Ash | Approximately 0.3–0.5 g |
| Energy | Approximately 40–50 kcal |
One detailed compositional study reported approximately 9.53% total solids, 1.57% protein, 1.16% fat, 6.33% lactose and 0.4% ash. Other studies have reported somewhat different values because donkey-milk composition changes during lactation and among breeds.
2. Chemical Similarities to Human Milk
A. Relatively Low Fat Content
- Donkey milk generally contains much less fat than cow milk.
- Its relatively low fat concentration contributes to its comparatively low energy density.
- The fatty-acid profile contains both saturated and unsaturated fatty acids, including essential fatty acids such as linoleic and α-linolenic acids.
- Fat globule characteristics differ from those of ruminant milk and contribute to the physical properties of donkey milk.
The low fat concentration is one of the important differences between donkey and human milk. Although the two milks have several compositional similarities, donkey milk does not provide the same amount of fat and energy as human milk. This is particularly important when considering its nutritional suitability for infants.
B. Protein Profile
Donkey milk has a relatively low total protein concentration and a high proportion of whey proteins compared with cow milk. This whey-dominant protein profile is one of the reasons for its compositional similarity to human milk.
| Feature | Donkey Milk | Human Milk | Cow Milk |
|---|---|---|---|
| Total protein | About 1.3–2.0 g/100 mL | About 1 g/100 mL | About 3–3.5 g/100 mL |
| Casein:whey relationship | Whey-rich | Whey-rich | Casein-rich |
| β-lactoglobulin | Present; amount varies | Absent or negligible | Present |
| α-lactalbumin | Important whey protein | Important whey protein | Present |
| Lysozyme | Relatively high | High | Very low |
| Lactoferrin | Present | Present | Present at lower concentration |
C. High Lactose Content
Lactose is one of the most abundant components of donkey milk after water. Concentrations are commonly around 6–7%, making donkey milk considerably richer in lactose than cow milk and broadly similar to human milk.
Lactose provides an important source of carbohydrate and contributes to the characteristic sweetness of donkey milk. It also contributes to the osmotic balance of milk.
D. Bioactive and Protective Proteins
- Lysozyme: Donkey milk contains an unusually high concentration of lysozyme compared with bovine milk. Lysozyme is an antimicrobial enzyme that can damage bacterial cell walls.
- Lactoferrin: This iron-binding protein has antimicrobial and immunomodulatory properties and is present in donkey milk.
- α-Lactalbumin: An important whey protein that also contributes to the nutritional similarity between donkey and human milk.
- Immunoglobulins: Donkey milk contains immunoglobulins, although their concentrations and biological effects vary.
- Oligosaccharides: Donkey milk contains oligosaccharides, but their quantity and structural diversity are substantially lower than those found in human milk.
E. Minerals and Vitamin C
| Nutrient | Donkey Milk | Human Milk | Cow Milk |
|---|---|---|---|
| Calcium | Relatively high | Lower | Higher |
| Phosphorus | Moderate | Low | Higher |
| Sodium | Relatively low | Low | Higher |
| Potassium | Moderate | Moderate | Higher |
| Vitamin C | Approximately 30–60 mg/L | Approximately 30–50 mg/L | Approximately 10–20 mg/L |
Donkey milk is generally considered a relatively good source of calcium, and several reviews report appreciable concentrations of vitamin C and other micronutrients. However, values vary among animals, breeds and production conditions.
3. Comparison of Donkey, Human and Cow Milk
| Parameter | Donkey | Human | Cow |
|---|---|---|---|
| Energy (kcal/100 mL) | About 40–50 | About 65–70 | About 60–70 |
| Fat (g/100 mL) | About 0.5–1.5 | About 3–5 | About 3–4 |
| Protein (g/100 mL) | About 1.3–2.0 | About 1 | About 3–3.5 |
| Lactose (g/100 mL) | About 6–7 | About 6.5–7 | About 4.5–5 |
| Protein profile | Whey-rich | Whey-rich | Casein-rich |
| Lysozyme | High | High | Very low |
| β-lactoglobulin | Present; variable | Absent/negligible | Present |
| pH | Approximately neutral to slightly alkaline | Approximately neutral | Approximately 6.6–6.8 |
4. Donkey Milk and Cow's-Milk Protein Allergy
Donkey milk has been investigated as a possible alternative food for some children with cow's-milk protein allergy because its protein composition, relatively low casein concentration and whey-rich profile differ from bovine milk.
Clinical studies have reported good tolerability in many children with cow's-milk protein allergy. However, donkey milk is not suitable automatically for every allergic child, and allergic reactions can still occur. Its use in infants with food allergy should therefore be considered under appropriate medical and nutritional supervision.
5. Why Is Donkey Milk Considered Similar to Human Milk?
- Both contain relatively high concentrations of lactose.
- Both have relatively low casein concentrations compared with cow milk.
- Both have a relatively high proportion of whey proteins.
- Their average protein concentrations are much closer to each other than those of donkey and cow milk.
- Both contain bioactive proteins such as lysozyme and lactoferrin.
- Their mineral and fatty-acid profiles show several similarities, although important quantitative differences remain.
6. Important Limitations
The similarities between donkey and human milk should not be interpreted as meaning that the two milks are nutritionally identical. The most important difference is the much lower fat and energy content of donkey milk.
In addition, the composition of donkey milk varies considerably according to breed, lactation stage, feeding system, season and analytical method. Consequently, claims about exact nutrient concentrations or therapeutic effects should always be interpreted in the context of the underlying study.
7. Summary
Donkey milk is chemically distinctive because it combines a relatively low concentration of fat and protein with a high lactose concentration and a whey-rich protein profile. It also contains notable concentrations of bioactive proteins, particularly lysozyme, lactoferrin and α-lactalbumin.
These characteristics give donkey milk several compositional similarities to human milk and have stimulated research into its nutritional applications and possible use for some children with cow's-milk protein allergy. Nevertheless, donkey milk is not identical to human milk and should not be regarded as a pharmaceutical product or a universally appropriate infant food.
Current reviews support further research, particularly well-controlled human clinical studies, before strong therapeutic claims can be made.
Read also: Therapeutic & Clinical Uses of Donkey Milk
Related Topics
Chemistry of Human Milk
Chemistry of Cow Milk
Chemistry of Buffalo Milk
Chemistry of Goat Milk
Chemistry of Camel Milk
Chemistry of Sheep Milk