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What happens in the heart tissue of rats when they drink cow, donkey, or human milk in addition to their regular diet for four weeks? An Italian team from the Universities of Naples and Cagliari investigated exactly this, examining the mitochondria—the energy-producing “powerhouses” of the heart muscle cells. The three milk groups differed in several laboratory values: the cow milk group showed more body fat and lower mitochondrial respiration, while the donkey and human milk groups showed different redox and fatty acid values.
Animal study on healthy rats—no conclusions can be drawn about its effects on humans. Laboratory values were measured in the animals’ heart tissue and blood serum. Donkey milk is a food.
Study summary
| Feature | Information |
|---|---|
| Original title | Heart Mitochondrial Metabolic Flexibility and Redox Status Are Improved by Donkey and Human Milk Intake |
| Authors | Trinchese G., Cimmino F., Cavaliere G. et al. |
| Journal | Antioxidants, 10(11): 1807 |
| Year | 2021 |
| Country | Italy |
| Study type | Feeding trial in rats (animal model) |
| Sample | 28 male Wistar rats, 4 groups of 7, duration 4 weeks |
| DOI | 10.3390/antiox10111807 |
What question did the researchers ask?
Following earlier studies on the liver and skeletal muscle, this time the focus was on the heart: Did mitochondrial function, redox status (the balance between reactive oxygen compounds and the body’s own antioxidant systems), signaling substances, and fatty acids in the heart tissue differ depending on whether the animals received cow, donkey, or human milk?
How was the study conducted?
- Groups: 28 male Wistar rats (around 60 days old, averaging 345 g) were divided into four groups of 7: a control group without milk, and one group each receiving raw cow, donkey, or human milk.
- Equal energy: Each milk group received 82 kJ from milk daily. To achieve this, the animals drank 21 ml of cow milk, 48 ml of donkey milk, or 22 ml of human milk—in addition to their standard feed.
- Four-week assessment: Body weight and feed consumption were recorded daily, feces were collected, and body composition was determined at the end.
- Heart tissue: Mitochondria were isolated from the hearts and their oxygen consumption was measured. This was supplemented by enzyme activities, the MDA marker for lipid peroxidation (oxidatively altered fats), signaling substances, fatty acids, gene expression, and tissue sections.
The results
All three milk groups consumed a similar amount of usable energy, more than the control group. Only in the cow milk group were weight gain and body fat percentage higher than in the control group. The respiration of isolated heart mitochondria was lower in the cow milk group than in the control and donkey milk groups. In the donkey milk group, the release of hydrogen peroxide (H₂O₂) from the mitochondria was lower than in the cow and human milk groups. The MDA marker was highest in the cow milk group and lowest in the donkey and human milk groups. The signaling substances TNF-α and IL-1α in the serum and heart tissue of the rats were lower in the donkey and human milk groups, while IL-10 was higher. The tables on fatty acids and endocannabinoids (the body’s own signaling substances) provide the figures:
| Measurement in heart tissue | Control | Cow milk | Donkey milk | Human milk |
|---|---|---|---|---|
| DHA (omega-3), nmol/g | 8.938,36 | 9.616,58 | 11.132,58 | 10.290,31 |
| Myristic acid (14:0), nmol/g | 218,29 | 467,59 | 228,89 | 251,69 |
| Arachidonic acid, nmol/g | 13.445,11 | 13.201,11 | 13.963,23 | 14.381,91 |
| Anandamide (AEA), pmol/g | 55,56 | 45,74 | 21,54 | 27,34 |
| DHEA, pmol/g | 126,03 | 132,81 | 78,59 | 97,92 |
These are the averages for 7 animals each. DHA was statistically higher in the donkey milk group than in the control and cow milk groups; myristic acid was higher in the cow milk group than in the control group; arachidonic acid showed no difference. AEA and DHEA were lower in the donkey milk group—the authors themselves describe this as “unexpected.”
In healthy rats, several laboratory values in the heart tissue differed depending on the type of milk after four weeks of milk supplementation. The study cannot determine what these differences mean—let alone for humans.
Critical assessment
- Small groups: Seven animals per group, and the gene expression data are based on only three animals per group.
- Limited design: Only healthy male rats over four weeks. The control group did not receive a comparison drink with the same energy content or volume.
- Unequal drinking volumes: To achieve the same energy content, the animals drank more than twice as much donkey milk as cow or human milk. It was not tested whether the volume of liquid itself played a role.
- Presentation: Many results are only presented as bar charts in the paper; the tables contain typos (e.g., “14,4424.90”). The tissue sections were only described, not measured.
- Evaluative title: “Improved” is the authors’ interpretation. The feeding followed the design of earlier studies by the same group; it remains unclear in the text whether the same animals were analyzed.
Funding, conflicts of interest, and level of evidence
According to the paper, the study received no external funding; the authors declare no conflicts of interest. They work at universities in Naples and Cagliari, a Milanese clinical network, and the Italian National Research Council (CNR). The animal study was approved by the Italian Ministry of Health.
Level of evidence: preclinical (animal model using healthy rats)—describes laboratory values in heart tissue and cannot be used to draw conclusions about effects on humans.
What does this mean for donkey milk as a food?
The study shows above all that cow, donkey, and human milk differ in their composition and that rats showed different laboratory values after several weeks of supplementation. The authors suspect a connection with the fatty acids in the different types of milk, but they did not test this. No recommendation for humans can be drawn from the study.
Our research question: How stable is the fatty acid profile of donkey milk across seasons and farms—and how can we transparently show its composition?
Frequently asked questions
Did the rats only receive milk?
No. All animals had free access to standard feed and water. The milk was added daily in the same energy amount; the control group received no milk.
Why did the animals drink so much more donkey milk?
Donkey milk contains less fat and therefore less energy per milliliter. To achieve the same 82 kJ, 48 ml were required, compared with 21 ml of cow milk and 22 ml of human milk.
Can the results be applied to humans?
No. This was a small animal study on healthy rats. The measurements describe differences in the animals’ heart tissue, not effects on humans.
You can find all measurements, interactive graphics, and the full critical assessment on our research page: Study 82: Three Types of Milk and Heart Mitochondria in Rats. More studies in the research archive.
Trinchese G., Cimmino F., Cavaliere G. et al. (2021). Heart Mitochondrial Metabolic Flexibility and Redox Status Are Improved by Donkey and Human Milk Intake. Antioxidants, 10, 1807. DOI: 10.3390/antiox10111807
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 study summary. The study was conducted independently of DON DONKEY'S® and does not refer to our products. Our donkey milk is a food.
