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Research on donkey milk · Study 93
Roughage and aroma compounds in donkey milk
27 jennies received maize straw, wheat husks or wheat straw for six weeks. 43 volatile compounds were detected in the milk; 23 of them distinguished the feed groups statistically.
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The key figures
Study design
How it was studied
27 jennies (5 years old, 60 ± 15 days in lactation, 286 ± 25 kg), described in the study as healthy, were randomly allocated to three groups of 9 animals each. The ration consisted of 80 % roughage – maize straw (G1), wheat husks (G2) or wheat straw (G3) – and the rest (maize, soya, premix, salt) was identical. The trial lasted 6 weeks (2-week pre-period, 4-week main period); at the end, one milk sample was taken from each jenny and stored at −80 °C. The volatile compounds (VOCs) were determined by gas chromatography–ion mobility spectrometry (GC-IMS) and evaluated with relative odour activity values (ROAV) and OPLS-DA multivariate analysis.
Interactive chart · values from the study
Selected aroma compounds by roughage (standardised intensity)
Means from Table 3 of the study (n = 9 per group), after normalisation, log transformation and Pareto scaling; relative signal intensities, not concentrations.
Second analysis
43 volatile compounds by compound class
Shares according to the study: 27.91 %, 25.58 %, 18.60 %, 16.28 %, 2.33 % each and 4.65 %.
Results
What the study measured
In the milk of all groups, the authors detected 43 volatile compounds: 12 esters (27.91 %), 11 ketones (25.58 %), 8 aldehydes (18.60 %), 7 alcohols (16.28 %), one pyrrole, one alkene and one acid (2.33 % each) and 2 unidentified compounds (4.65 %). Ketones and esters were the most common.
Milk from the maize straw group (G1) contained significantly more esters (P < 0.05) and aldehydes (P < 0.001) than the two wheat groups; alcohols were higher in G1 than in G2. Alkenes (1-phellandrene), by contrast, were highest in the wheat straw group (G3) and lowest in G1 (P < 0.001); the pyrrole was lower in G3.
13 compounds had a relative odour activity value (ROAV) above 1 and are regarded in the study as characteristic aroma compounds: five aldehydes, four esters and four ketones. The largest contributions came from methyl thiocyanate, ethyl acetate and hexanal.
OPLS-DA analysis separated the three groups; 23 compounds with VIP > 1 served as possible markers (9 esters, 8 aldehydes, 2 alcohols and 2 ketones, 1 alkene and 1 pyrrole). For example, (E)-hept-2-enal was 278.29 in G1, 55.17 in G2 and 58.62 in G3 (standardised intensity); ethyl 2-methylpropanoate (monomer) 1324.89, 382.52 and 311.02.
Some compounds were higher in the wheat groups, such as allyl isothiocyanate (G1 188.22; G2 387.98; G3 370.23) and amyl acetate dimer (126.06; 160.75; 202.46).
The authors attributed the higher ester and aldehyde values in G1 to the higher crude fat content of maize straw (1.90 % of DM compared with 1.27 % and 1.02 %). This explanation was not tested directly in the study.
Authors’ conclusion: The authors concluded that the volatile compounds of donkey milk – especially esters and aldehydes – were influenced mainly by the type of roughage, and saw this as a theoretical basis for steering the aroma profile of donkey milk via roughage.
Critical assessment
Strengths and limitations
No tasting
Only instrumental measurements were made; there was no sensory panel. The odour descriptions (e.g. grassy, fruity) come from the literature, not from the study’s own tests.
Relative values only
According to the methods section, peak areas do not allow amounts or concentrations to be calculated. All group comparisons are based on normalised, relative signal intensities.
Errors in Table 3
Table 3 is titled “donkey meat” instead of milk. Several values are obviously typeset incorrectly (e.g. “723.60 3.20.54b”, “1024.40 2448.26c”), and some significance letters contradict the main text (e.g. hexanal monomer: highest value in G1 marked “c”).
Questionable assignments
Some database assignments are chemically questionable: at least one assigned compound does not seem plausible in milk; 2-propanethiol is classed as an alcohol, allyl isothiocyanate as an ester. The discussion also refers to the rumen, although donkeys are not ruminants.
Limited sample
9 animals per group, a single milk sample per animal at the end of the trial, one site in China. The conclusion speaks of seven compound classes, the results section of eight.
Controlled feeding design
Randomised groups, same husbandry and feeding times, identical ration apart from the roughage, six-week trial duration and ethics approval; the roughage analyses are reported in full.
Editorial assessment: The study measures aroma compounds instrumentally and in relative terms; whether people can taste or smell the differences was not examined. To the research archive.
Research question for DON DONKEY’S®
Do consumers actually perceive the feed-related differences in the aroma profile of donkey milk in a tasting?
Original publication
Characterization and discrimination of milk volatiles from donkey fed different roughages using GC-IMS
Original title of the publication.
Du X., Zhao Y., Ding L., Huang F., Ren W., Ma Z., Zhu M., Liu G., Khan M. Z., Wang C., Zhou M., Li M.
Frontiers in Nutrition · 2025 · volume 12, article 1652665
College of Agriculture and Biology, Liaocheng Research Institute of Donkey High-Efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China
10.3389/fnut.2025.1652665: 10.3389/fnut.2025.1652665
Transparency: funded by the National Key R&D Program of China (2022YFD1600103, 2023YFD1302004), the Shandong Provincial Natural Science Foundation (ZR2022QC130), the donkey industry innovation team of the Modern Agricultural Technology System of Shandong Province (SDAIT-27), the Support Program for Innovation and Technology in Universities of Shandong Province (2023KJ354) and the Livestock and Poultry Breeds Project of the Chinese Ministry of Agriculture (19211162). The authors declare no commercial or financial relationships that could be construed as a potential conflict 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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