Donkey Milk Study: Composition Over 180 Days (Zhou 2025)

Contents

1. Study at a glance
2. Study methodology
3. Key figures
4. Results
5. Critical assessment
6. Funding, conflicts of interest and level of evidence
7. Our assessment

In six Dezhou donkeys, the milk fat content decreased from 0.92% on the first day to 0.09–0.20% by day 90, while lactose increased from 3.94% to up to 6.85%. Hormones and blood parameters of the animals were also recorded.

Study at a glance

Feature	Information
Original title	The Milk Compositions and Blood Parameters of Lactating Dezhou Donkeys Changes With Lactation Stages
Authors	Zhou M., Ma Z., Du X. et al.
Journal	Veterinary Medicine and Science, 11(2), e70269
Year	2025
Country	China
Study type	Animal study
DOI	10.1002/vms3.70269

Study methodology

Six healthy multiparous Dezhou donkeys (average age 5 years, 284 ± 21 kg) from a farm in Dong'E (Shandong Province, China) were sampled on lactation days 1, 30, 60, 90, 120, 150 and 180. All animals received the same ration of bean straw ad libitum plus 2 kg of concentrate per animal per day and were milked by hand twice daily; the foals were separated 4 hours before milking each time. Fat, protein, lactose, urea, lactoferrin and dry matter were determined using an FTIR spectrometer (CombiScope FTIR300), while the minerals Ca, P, K, Na, Mg, Zn and Se were measured by ICP-MS. Hormones (ELISA) and clinical biochemical parameters were measured in the blood serum; the data were analyzed using one-way ANOVA with repeated measures as well as correlation analyses.

Key figures

Value	Meaning
6	multiparous Dezhou donkeys, sampled at 7 time points (days 1 to 180)
0.92 %	Milk fat content on lactation day 1
0.09 %	Lowest fat content (day 150)
7.67 %	Protein content on day 1 (± 2.61)
1.39 %	Protein content on day 180
3.94 %	Lactose content on day 1 (lowest value)
6.85 %	Lactose content on day 120 (highest value)
0.085 g/L	Lactoferrin on day 1; days 60, 120 and 150: 0.094 g/L each

Results

Fat, protein, dry matter and fat-free dry matter were highest in colostrum (day 1), followed by day 30. The fat content decreased from 0.92% to 0.43% (day 30) and thereafter ranged between 0.09% and 0.20%; the protein content decreased from 7.67% to 1.39% on day 180.

Lactose showed the opposite trend: It was 3.94% on day 1 and reached values of 6.69% to 6.85% between days 90 and 180. Lactoferrin also increased from 0.085 g/L on day 1 to 0.091–0.094 g/L. Milk urea (12.92–15.20 mg/dL) showed no significant influence of the lactation stage (p = 0.0796).

For the period from day 30 to 180, the authors report average contents of 9.15% dry matter, 6.66% lactose, 1.54% protein, 0.20% fat and 0.093 g/L lactoferrin.

Mineral contents were predominantly highest in colostrum: potassium 1463.82 mg/kg, magnesium 414.09 mg/kg, sodium 260.33 mg/kg and selenium 66.77 µg/kg. Calcium decreased from 935.69 mg/kg (day 1) or 957.20 mg/kg (day 30) to 592.59 mg/kg on day 180; phosphorus was higher on days 1–60 than on days 90–180.

The tabulated milk yield ranged between 1137 g and 575 g; according to the discussion, it decreased from 1.137 kg/d to 0.575 kg/d, with an average of 0.858 kg/d. The peak phase is stated in the abstract as days 30–60, and in the discussion as days 30–90.

In the donkeys' blood, prolactin, IGF-1, glucose, total protein, albumin, cholesterol, triglycerides, HDL, LDL and LDH were higher at the start of lactation. Milk yield correlated positively with prolactin (r = 0.82) and IGF-1 (r = 0.83); milk fat, protein and dry matter correlated, among others, with blood glucose (r = 0.97–0.98) and triglycerides (r = 0.91–1.00).

Critical assessment

• Limitation – Small, uniform sample: Only six donkeys of one breed from a farm with uniform feeding were examined. The values cannot easily be generalized to other breeds, housing systems or commercial products.
• Note – Unclear milk yield data: The table row for milk yield contains only six values for seven time points and the unit "g" without a time reference; the discussion assigns 1.137 kg/d to day 60. In addition, only the yield after 4 hours of foal separation was recorded, not the total milk production.
• Note – Units and designations: Zinc is given in µg/kg in Table 5, and as 2.64 mg/kg in the discussion. In the abstract, the abbreviations for total cholesterol and triglycerides are swapped, and the discussion mentions iron, which was not measured according to the methods section.
• Note – Method and interpretation: Milk constituents including lactoferrin were determined by FTIR; no calibration for donkey milk is described. Blood values are only available as figures, correlations do not prove causation, and the interpretation of ALP values as an indication of liver function and bone mineral loss was not directly tested.
• Strength – Longitudinal study with repeated measures: The same animals were followed over seven time points up to day 180, and milk and blood were analyzed in parallel. The analysis takes repeated measures into account, and raw values with standard deviations are provided in tables.

Funding, conflicts of interest and level of evidence

Key Technology Research and Development Program of Shandong (2021TZXD012), Shandong Provincial Natural Science Foundation (ZR2023MC149), National Key R & D Program of China (2022YFD1600103) as well as Open Project of Liaocheng University Animal Husbandry Discipline (319312105-5).

The authors declare that there are no conflicts of interest.

Level of evidence: Animal study – describes measured values in the examined animals and their milk, no statement on effects in humans.

Our assessment

The study describes raw milk from a Chinese donkey breed under defined housing conditions and provides measured values of its composition. No conclusions on health effects in humans or on individual commercial products can be drawn from it.

Open research question: Do other donkey breeds and housing systems show the same trend in fat, protein, lactose and minerals during lactation?

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.

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End of study summary. The study was conducted independently by DON DONKEY'S® and does not refer to our products. Our donkey milk is a food.