Research on donkey milk · Study 87

Two hours before milking: separating jenny and foal

On many donkey farms, mare and foal are separated for a while before milking. A Brazilian team measured in 14 Pêga jennies how behaviour and cortisol in saliva change in the process – and how much milk was obtained per milking.

Important: An observational study on the milking routine of jennies and foals on one farm. It measures behaviour, salivary cortisol and milk yield and does not examine any effect of donkey milk in humans.

Saliva sampleSeparation 10 am–12 noonMilking by hand

The farm · tap a plot

Pasture, stable, milking area

Schematic, not to scale. The paper does not describe how the areas are positioned relative to each other.

Milk yield

566.4 mL per milking – with a wide range

Band = mean ± one standard deviation (361.2 to 771.6 mL, calculated from the data). Scale in mL per milking.

566.4 mLmean per jenny and milking, ± 205.2 mL standard deviation

≈ 0.6 kgauthors’ conversion with a density of 1.03 g/mL – about 0.25 % of body weight

up to 4.8 kgauthors’ extrapolation per day with up to eight milkings – not measured

Seven measurement days · runs automatically, tappable

Every 15 days one step

Cortisol jennies
Cortisol foals

Before versus after

Where something changed measurably

Columns: day of lactation 45 to 135. Each dot is a before–after comparison on a measurement day. Filled = significant (p < 0.05). The smaller the p-value, the larger the dot. For vocalisations, the paper gives a value only for day 120; the other days are described as not significant.

790 pg/µLsalivary cortisol of the jennies before separation, mean (217.93 nmol/L) · 8:50–9:50 am

840 pg/µLsalivary cortisol of the jennies after separation, mean (231.72 nmol/L) · 12 noon–2 pm

Critical assessment

Six slats in the pasture fence

No control group

There were no animals without separation. Before–after comparisons on the same day also capture time-of-day effects.

No true baseline

The authors themselves state that true baseline values of salivary cortisol and behavioural observations of the foals are missing.

Little milk data

Milk was recorded only once per measurement day. Values per measurement day are not reported.

Up to 3 hours

Because all 14 animals were examined at the same time, some were separated for up to three hours.

Inconsistencies

Text and Figure 2 are not clear about the abnormal behaviour on day 120. The date of ethics approval (17.11.2019) is after the data collection in 2018.

Openly stated limits

The authors name their limitations clearly; funding is public (CNPq), no conflicts of interest declared.

clear limitationnotestrength

Editorial assessment: The study describes a single milking routine on a farm without a dairy operation. Whether separation is stressful can be inferred only to a limited extent from salivary cortisol and short behavioural observations. The authors themselves write that it is “possibly” not stressful. For milk yield over the year, compare Study 86.

Research question for DON DONKEY’S®

How can a milking routine be described transparently?

Separation time, milking times and milk yield per milking differ from farm to farm. Which details of the milking routine are meaningful and verifiable is a question we are following up.

Document milking timesCompare with Study 86Look for studies with a control group

Original publication

Two Hours of Separation Prior to Milking: Is This Strategy Stressful for Jennies and Their Foals?

Original title of the publication.

de Souza Farias S., Dierings Montechese A. C., Bernardino T., Mazza Rodrigues P. H., Albano de Araujo Oliveira C., Zanella A. J.
Animals · 2021 · volume 11, issue 1, article 178 · open access
University of São Paulo (Pirassununga) and Federal University of Bahia (Salvador), Brazil

DOI: 10.3390/ani11010178

Transparency: funded by the Brazilian research council CNPq. 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

End of the study summary

Note on our products

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.

From our shop

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.

Transparency: The study observed Pêga jennies on a farm in Brazil – not the animals of our partner farms.

€24,90

100 ml bottle / 100ml · Unit price: €249,00 / 1 l · incl. VAT, plus shipping

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Also in our shop

Donkey Milk Powder

Donkey milk in powder form

For anyone who prefers a longer shelf life: our donkey milk in powder form – easy to store and portion.

Transparency: The study was about the milking routine, not our donkey milk powder.