Buyer protection
Contents
Does a probiotic in feed change the milk of donkeys? An Italian team investigated 20 Ragusana donkeys: ten received a probiotic for 30 days, while ten ate their usual feed. They measured the small molecules in the milk (the metabolome) and two enzyme activities, as well as the differences between colostrum and mature milk. Some values shifted, but the work contains a striking number of inconsistencies.
Feeding trial in 20 donkeys with milk analysis – no statement about an effect in humans. Donkey milk is a food.
Study at a glance
| Feature | Information |
|---|---|
| Original title | Donkey Colostrum and Milk: How Dietary Probiotics Can Affect Metabolomic Profile, Alkaline Sphingomyelinase and Alkaline Phosphatase Activity |
| Authors | Laus F., Laghi L., Bazzano M. et al. |
| Journal | Metabolites, 13(5): 622 |
| Year | 2023 |
| Country | Italy |
| Study type | Randomized feeding trial in donkeys with milk analysis |
| Sample | 20 Ragusana donkeys, randomly assigned to the probiotic and control groups |
| DOI | 10.3390/metabo13050622 |
What question did the researchers ask?
Probiotics – live bacteria as a feed additive – have long been studied in dairy cows. There was little data on donkeys. The researchers wanted to know: Does a probiotic in feed change the composition of the milk? And can two enzymes that are normally barely detectable in donkey milk be measured?
How it was investigated
- Animals: 20 clinically healthy Ragusana donkeys, 5 to 10 years old, fed around 6 kg of hay and 0.5 kg of concentrate per day.
- Supplement: From day 15 of lactation, ten animals received 18 g of a probiotic containing eight strains of lactic acid bacteria and bifidobacteria daily for 30 days.
- Samples: Colostrum within 48 hours of parturition, milk on day 15 and day 45 – hand-milked in the morning.
- Measurement: Nuclear magnetic resonance spectroscopy (¹H-NMR) for the small molecules, plus tests for two enzymes: alkaline sphingomyelinase and alkaline phosphatase (ALP).
The results
In total, the team identified 76 metabolites, i.e., small metabolic molecules. Between colostrum and milk on day 15, 18 of them differed. After 30 days of supplementation, 12 molecules in the milk of the probiotic group differed from those in the control group.
| Measurement (milk on day 45, mmol/L) | Control | Probiotic |
|---|---|---|
| Lactose | 177.382 | 193.809 |
| O-Phosphocholine | 0.068 | 0.172 |
| 4-Pyridoxate | 0.183 | 0.267 |
| Butyrate | 0.201 | 0.070 |
| Caprylate | 0.728 | 0.408 |
| Glutamine | 1.255 | 0.841 |
Alkaline phosphatase was not detectable in colostrum, in the milk on day 15, or in the control group. In the probiotic group, it was above the detection limit (0.97 to 11.73 U/mL) in six out of ten animals. Alkaline sphingomyelinase was higher in colostrum than on day 15 and moderately higher after supplementation than in the control group; the paper only shows the figures for this.
After 30 days of probiotic supplementation, some small molecules and two enzyme activities differed in the milk – in a small trial with several inconsistencies.
Critical assessment
- Swapped labels: In Table 3, the groups are labeled in reverse order compared to the methods section. We follow the methods and text, which match.
- Implausible value: For ethanol, the study reports values around 260 to 320 mmol/L. This would correspond to more than 1 g of alcohol per 100 mL of milk – implausible for fresh milk and not explained in the paper.
- Measurement standard: The added reference substance (TSP) differed significantly between the groups. This raises doubts about the normalization of the values.
- Text contradicts table: The discussion describes an increase in several substances in the milk, while the results section shows a decrease.
- Small trial: Ten animals per group, one breed, 30 days. Whether it was measured blindly is not stated in the paper.
Funding, conflicts of interest and level of evidence
According to the paper, there was no external funding, and the authors state that there are no conflicts of interest. They work at the Universities of Camerino, Bologna, and L’Aquila. We deliberately do not mention the name of the probiotic used.
Level of evidence: Feeding trial in donkeys with milk analysis – describes changes in the milk, no statement about effects in humans.
What does this mean for donkey milk as a food?
The study suggests that feeding can shift the small molecules in the milk, and it shows differences between colostrum and mature milk. The authors draw parallels to gut health, tumors, and infant nutrition. None of this was investigated. Donkey milk is not a substitute for breast milk or infant formula. That ALP became measurable after supplementation is described by the authors as a possible approach for testing procedures; no recommendation can be derived from this.
Our research question: How strongly does regular feeding shape the small molecules in the milk – and how do we transparently describe the feeding of our partner farms?
Frequently asked questions
What is a metabolome?
The totality of the small molecules in a sample, for example sugars, amino acids, and short-chain fatty acids. Here it was measured using nuclear magnetic resonance.
What is alkaline phosphatase?
An enzyme that naturally occurs in milk. In cow milk, it serves as a test value for pasteurization; in donkey milk, it is usually barely detectable.
How did colostrum and mature milk differ?
18 of 76 molecules had different levels. Uridine, for example, dropped from 0.565 to 0.187 mmol/L, while caprylate rose from 0.271 to 0.635 mmol/L.
You can find all measurement values, interactive graphics, and the full critical assessment on our research page: Study 73: Probiotics in Feed and Milk Metabolome. Further studies in the research archive.
Laus F., Laghi L., Bazzano M., Cifone M. G., Cinque B., Yang Y., Marchegiani A. (2023). Donkey Colostrum and Milk: How Dietary Probiotics Can Affect Metabolomic Profile, Alkaline Sphingomyelinase and Alkaline Phosphatase Activity. Metabolites, 13(5), 622. DOI: 10.3390/metabo13050622
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.
