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Colostrum is the first milk after birth. A team from the Inner Mongolia Agricultural University investigated how many minerals are in it and in the milk of the first two weeks – and whether the feed in late pregnancy plays a role. For this, 24 Dezhou donkeys received rations with three energy levels. The most important observation: All measured minerals were highest immediately after birth and dropped significantly by day 14; the group with medium energy usually had the highest values.
Feeding trial on donkeys with laboratory analysis – no statement about an effect in humans. Donkey milk is a food.
The study at a glance
| Feature | Information |
|---|---|
| Original title | Effect of Dietary Energy Level during Late Gestation on Mineral Contents in Colostrum, Milk, and Plasma of Lactating Jennies |
| Authors | Hui F., Tong M., Li S. et al. |
| Journal | Animals, 14(16): 2383 |
| Year | 2024 |
| Country | China (Hohhot, Inner Mongolia) |
| Study type | Randomized feeding trial with milk and plasma analysis |
| Sample | 24 pregnant, multiparous Dezhou donkeys in three groups |
| DOI | 10.3390/ani14162383 |
What question did the researchers ask?
Does the energy level in the feed during the last weeks of pregnancy change the contents of minerals (for example calcium, potassium) and trace elements (for example zinc, selenium) in the colostrum, milk, and blood plasma of the donkeys? And how do these values develop in the first 14 days after birth?
How it was investigated
- Animals: 24 multiparous Dezhou donkeys (6.0 ± 0.1 years) were randomly assigned to three groups and kept in individual pens.
- Feed: After 14 days of acclimation, rations with 12.54, 12.03, or 11.39 MJ of digestible energy per kg (high, medium, low) were provided for 60 days. After birth, all received the same lactation feed every 14 days.
- Milking: By hand at around 10 and 17 hours; the foals were separated three hours beforehand each time. Morning and afternoon milk were mixed in equal parts.
- Analysis: Samples at birth (0 h), after 24 and 48 hours, and after 5, 7, and 14 days. Minerals by ICP-OES, a common laboratory method for determining elements.
The results
All eleven measured elements dropped significantly after birth, most rapidly in the first 24 to 48 hours. The table shows the averages across all three groups.
| Measurement | 0 h | 24 h | 7 days | 14 days |
|---|---|---|---|---|
| Calcium (mg/L) | 1,351.11 | 1,232.54 | 1,043.70 | 888.89 |
| Potassium (mg/L) | 1,539.78 | 1,278.12 | 465.73 | 359.17 |
| Magnesium (mg/L) | 472.26 | 149.60 | 78.99 | 65.86 |
| Zinc (µg/100 mL) | 270.49 | 199.35 | 99.26 | 84.57 |
| Iron (µg/100 mL) | 278.47 | 232.04 | 156.87 | 128.71 |
Among the feed groups, the medium energy level was ahead for calcium, phosphorus, potassium, magnesium, iron, copper, zinc, and molybdenum. Calcium, for example: 1,172.98 mg/L (medium) compared to 1,079.43 mg/L (high) and 1,110.8 mg/L (low), each averaged over all time points. For manganese, selenium, and cobalt, the medium and low energy levels were tied for first place before the high. Similar patterns were found in the blood plasma.
Colostrum contained significantly more minerals than the milk two weeks later. The energy level in the feed before birth was associated with measurable differences, with the medium level usually having the highest values.
Critical assessment
- Group size: 24 animals in three groups – eight per group is obvious, but is not explicitly stated in the text.
- Inconsistencies: The calcium range is stated as 1043.7–1351.11 mg/L in the results section, and 888.89–1351.11 mg/L in the discussion. The body weight is stated once as ±33 kg and once as ±34 kg in the text.
- Short period: Measurements were only taken up to day 14. The study says nothing about mature milk in later months.
- Sampling: It is not stated whether the 0-h sample was taken before the foal's first suckling.
- Scale: The energy of the rations was calculated according to the horse standard (NRC 2007). The requirements of donkeys may differ from this.
Funding, conflicts of interest, and level of evidence
The work was funded by programs of the Autonomous Region of Inner Mongolia. The authors declare no conflicts of interest. The trial was approved by the university's animal ethics committee.
Level of evidence: Feeding trial on livestock with laboratory analysis – describes mineral contents in colostrum and milk, no statement about effects in humans.
What does that mean for donkey milk as a food?
The study shows that the mineral contents change significantly in the first days after birth. Colostrum and mature milk are therefore not comparable. The authors describe donkey milk as a "functional food" – we do not adopt this classification, because only contents were measured, no effects.
Our research question: How stable are the mineral contents in mature milk over the further lactation – and how do we present the laboratory values of our batches clearly?
Frequently asked questions
What is colostrum?
The first milk immediately after birth. It differs significantly in composition from later milk. In this study, all measured minerals were highest in the colostrum.
How quickly did the values drop?
Very differently. Magnesium dropped from 472.26 to 149.60 mg/L in 24 hours. Calcium dropped more slowly, from 1,351.11 to 888.89 mg/L in 14 days.
More feed energy, more minerals?
No, not in this study. The group with the highest energy had numerically the lowest values everywhere, the medium level usually the highest.
You can find all measurements, interactive graphics, and the complete critical assessment on our research page: Study 88: Minerals in Colostrum and Milk. Further studies in the research archive.
Hui F., Tong M., Li S., Zhao Y., Guo X., Guo Y., Shi B., Yan S. (2024). Effect of Dietary Energy Level during Late Gestation on Mineral Contents in Colostrum, Milk, and Plasma of Lactating Jennies. Animals, 14(16), 2383. DOI: 10.3390/ani14162383
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 by DON DONKEY'S® and does not refer to our products. Our donkey milk is a food.
