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Research on donkey milk · Study 86
Milk yield over the year: lactation, foaling and season in Amiata jennies
How much milk does a jenny give – and what does it depend on? A team from the University of Pisa followed 20 dairy jennies over ten months and measured milk yield, composition, blood count and hair cortisol.
The jennies lived outdoors in semi-intensive husbandry and received mixed hay ad libitum and about 2.5 kg of concentrate per animal per day. In the first month the milk went entirely to the foal; milking started from day 30. Before each milking, the foals were separated from their mothers for four hours. The analysis looked at how lactation stage, number of foalings (parity) and season relate to the measurements.
Course of lactation · runs automatically
Three milk pails, three time points
Fill level proportional to mean daily milk yield (least-squares means). No significant difference between the 1st and 6th month; the 10th month was clearly lower (p = 0.001). Protein fell and urea rose (both p = 0.001). Fat, casein, lactose and dry matter did not change significantly. Cell count according to the table “number × 1000”.
Season · tap a measure
Spring–summer versus autumn–winter
- Spring–summer
- Autumn–winter
- p-value
In the wheel, the area of each half corresponds to the season’s measured value (spring–summer on the right, autumn–winter on the left). 12 jennies foaled in spring–summer, 8 in autumn–winter.
Number of foalings
First, second, further lactation
5 primiparous, 7 secondiparous, 8 multiparous. Casein and protein decreased with each foaling. Fat content was lowest in the primiparous jennies (0.16 %). Daily milk yield did not differ significantly (p = 0.468). Each axis starts at zero.
Measured alongside the milk
Hair cortisol and blood count
Cortisol in mane hair
The hormone is deposited in growing hair and is regarded as a long-term measure. In the 1st month it was higher than later (p = 0.010). The authors interpret this as temporary strain around the birth.
pg/mg hair. Parity and season: no significant difference.
Blood count
The white blood cell count was highest in the secondiparous jennies (14.38 × 10⁹/L) and lowest in the multiparous ones (11.49 × 10⁹/L). The values MCH and MCHC (haemoglobin per blood cell) were lower in spring–summer than in autumn–winter. The authors see this as a possible adaptation to the environment and call for donkey-specific reference values.
These are blood values of the jennies, not properties of the milk.
Critical assessment
Six test strips for this study
Small groups
20 jennies, one farm, one breed. The smallest group (primiparous) had only five animals.
The value in the 1st month
In the first month the foal received all the milk; milking began from day 30. The paper does not describe exactly how the 1-month value was obtained.
Large spread
The error term (RMSE) of daily milk was 425 mL – individual jennies deviated strongly from the mean.
Unequal season groups
12 versus 8 jennies. Interactions between lactation stage, parity and season are not reported in the tables.
Interpretation of the cell count
The authors interpret the increase in the 10th month as a possible natural involution of the mammary gland. That is an interpretation, not a measurement of their own.
Clean repeated-measures design
The same animals at three time points, ethics approval from the University of Pisa, funding from the university, no conflicts of interest declared.
Editorial assessment: The study describes milk yield and composition under the conditions of a single farm. The figures cannot simply be transferred to other breeds, feeding or milking routines. For comparison: Study 55 (course of lactation in Romania) and Study 54 (feed and lactation in Italy).
Research question for DON DONKEY’S®
How much does the milk vary over a year?
In this study, protein, casein and lactose depended on lactation stage, parity or season. How large such variations are with hand milking and other husbandry – and how we can present them transparently – is a question we are following up.
Original publication
Impact of Variability Factors on Hair Cortisol, Blood Count and Milk Production of Donkeys
Original title of the publication.
Salari F., Mariti C., Altomonte I., Gazzano A., Martini M.
Animals · 2022 · volume 12, article 3009 · open access
Department of Veterinary Science, Università di Pisa (Italy)
DOI: 10.3390/ani12213009
Transparency: funded by the University of Pisa (PRA 2017, project on the milk yield of dairy donkeys). The authors declare no conflicts of interest. No product-related statement for DON DONKEY’S®.
Summarised and reviewed by the DON DONKEY’S editorial team on the basis of the original publication · as of October 2026
The study summarised above was carried out independently of DON DONKEY’S® and does not relate to our products. It serves solely to inform about the state of research.
DON DONKEY’S® donkey milk and donkey milk powder are foods. They are not intended to prevent, treat or cure any disease and do not replace medical advice.
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DON DONKEY’S® donkey milk
100 % donkey milk · raw milk, frozen
On this page we report the findings of a published study. Independently of that, you will find our donkey milk here: 100 % donkey milk, frozen as raw milk.
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