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How does donkey milk change over the course of lactation? A team from the Universities of Palermo and Catania followed nine Ragusano donkeys, a Sicilian breed, from the second to the ninth month of lactation. Milk yield was measured monthly, and protein, lactose, fat, and minerals were analyzed. The most important observation: daily milk yield remained stable at around 2 kg until approximately day 189 and then decreased significantly; protein and lactose levels declined over time.
Milk analysis of donkeys on a dairy farm – no statement about its effects in humans. Donkey milk is a food.
Study summary
| Feature | Information |
|---|---|
| Original title | New Insights into Chemical and Mineral Composition of Donkey Milk throughout Nine Months of Lactation |
| Authors | Malacarne M., Criscione A., Franceschi P. et al. |
| Journal | Animals, 9(12): 1161 |
| Year | 2019 |
| Country | Italy (Universities of Palermo and Catania) |
| Study type | Observational study with monthly milk analysis |
| Sample | 9 Ragusano donkeys, 62 individual samples |
| DOI | 10.3390/ani9121161 |
What question did the researchers ask?
How do milk yield, protein fractions, lactose, fat, and minerals in donkey milk change over a large part of lactation? And how are these values interrelated?
How was the study conducted?
- Animals: Nine Ragusano donkeys (6 to 16 years old, 320 to 350 kg) on a specialized dairy farm, at the beginning 40 to 69 days after birth.
- Feed and housing: Barn with access to pasture, 7 kg of pelleted mixed feed daily, plus hay and water at will.
- Milking: Twice daily by machine, at 11 a.m. and 3 p.m. The foals remained with their mothers from 3 p.m. to 6 a.m. Milk was measured after the foal had been separated.
- Analysis: Monthly milk yield and sample from the 11 a.m. milking. Protein by Kjeldahl, lactose and fat by infrared, minerals by atomic absorption.
The results
On average across all 62 samples, the donkeys produced 1.64 kg of milk per day (range 0.38 to 3.30 kg). The milk contained 6.07 g of lactose, 1.34 g of crude protein, and 0.16 g of fat per 100 g. Whey proteins made up the larger part of the protein at 0.78 g, casein 0.56 g.
| Lactation days | Milk (kg/day) | Lactose (g/100 g) | Crude protein (g/100 g) |
|---|---|---|---|
| 40–69 | 2.11 | 6.30 | 1.59 |
| 130–159 | 2.06 | 6.08 | 1.26 |
| 160–189 | 1.73 | 5.71 | 1.28 |
| 190–219 | 0.81 | 5.80 | 1.28 |
| 250–279 | 0.13 | 5.70 | 1.28 |
Among the minerals, potassium was highest at 110.27 mg/100 g, followed by calcium (54.36), sodium (43.77), and phosphorus (43.44 mg/100 g). Calcium and phosphorus decreased significantly after about 160 days, magnesium after about 190 days. Iron temporarily rose to 4.69 mg/kg (160 to 189 days). Potassium, chloride, and copper did not change significantly. Casein remained without significant difference throughout lactation.
In this herd, daily milk yield remained stable for around half a year and then dropped sharply. Protein, lactose, calcium, and phosphorus decreased over the course of lactation.
Critical assessment
- Small sample: Nine donkeys on one farm. In the last two periods, only five samples each were available.
- Not the full daily milk yield: Milk was collected between 6 a.m. and 3 p.m. after separation from the foal. What the foal drank is not included.
- Discrepant figures: The discussion states an average of 6.4 g of lactose and 1.6 g of protein per 100 g, while Table 1 shows 6.07 and 1.34 g.
- Ethics statement: According to the authors, the samples were taken during routine veterinary check-ups; no ethics approval number is provided.
- Content is not availability: Mineral contents were measured. How much of this the body can absorb was not investigated.
Funding, conflicts of interest, and level of evidence
The work was funded by the University of Palermo (Research Plan 2016–2018). The authors declare no conflicts of interest.
Level of evidence: Basic research (milk analysis) – describes quantity and composition, no statement about effects.
What does this mean for donkey milk as a food?
The study shows that donkey milk has a different composition depending on the stage of lactation: low fat, high lactose, whey proteins as the largest protein component. As lactation progressed, protein, lactose, calcium, and phosphorus decreased. The authors assess the milk as nutritionally interesting – we do not adopt this assessment; we report the measured values.
Our research question: Is it worth documenting the lactation stage of a batch – and how do we present such fluctuations transparently?
Frequently asked questions
How much milk did a Ragusano donkey produce?
On average 1.64 kg per day during the measured milking period. Until approximately day 189, the period values were between 1.73 and 2.11 kg, at the end 0.13 kg.
Which mineral was most abundant?
Potassium, with an average of 110.27 mg per 100 g of milk, followed by calcium, sodium, and phosphorus.
What are whey proteins?
Proteins that remain in the liquid whey when casein precipitates. In this study, they made up the larger part of the protein at 0.78 g per 100 g.
You can find all measured values, interactive graphics, and the full critical assessment on our research page: Study 89: Nine Months of Lactation in Ragusano Donkeys. Further studies in the research archive.
Malacarne M., Criscione A., Franceschi P., Bordonaro S., Formaggioni P., Marletta D., Summer A. (2019). New Insights into Chemical and Mineral Composition of Donkey Milk throughout Nine Months of Lactation. Animals, 9(12), 1161. DOI: 10.3390/ani9121161
Summarized and reviewed by the DON DONKEY'S editorial team based on the original publication · As of: October 2026. This summary does not replace the original work.
End of the study summary. The study was conducted independently of DON DONKEY'S® and does not refer to our products. Our donkey milk is a food.
