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Research on donkey milk · Study 107
Effect of dietary soybean and linseed oil on the lipid and aroma compound profile of donkey milk
28 jennies received soybean and linseed oil in four mixing ratios for four weeks. 1167 lipids and 406 volatile compounds were recorded in the milk; 64 lipids and 89 volatile compounds differed between the groups.
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The key figures
Study design
How it was studied
28 lactating three-year-old jennies on a farm in Shandong Province, China, were randomly allocated to four groups of seven animals each. The ration consisted of 80 % wheat straw plus maize, soya and a mineral and vitamin premix; 1 % of the ration was vegetable oil, a blend of soybean and linseed oil in the ratio 4:1 (M1), 3:2 (M2), 2:3 (M3) or 1:4 (M4). The animals were fed twice a day for four weeks in semi-open housing. At the end of the trial, one milk sample (100 mL) was taken per animal. Fat, protein, lactose, dry matter, urea, freezing point depression and polyunsaturated fatty acids were determined by FTIR milk analysis, the lipids by liquid chromatography–mass spectrometry (LC-MS) and the volatile compounds by headspace solid-phase microextraction with GC-MS. The analysis included ANOVA with post-hoc tests, OPLS-DA (criteria VIP > 1 and p < 0.05) and KEGG pathway analyses.
Interactive chart · values from the study
Milk composition by soybean/linseed oil ratio
Means ± SEM (n = 7) from Table 2; ratio of soybean oil to linseed oil. Lactose and solids-not-fat significantly lower in M3; fat and protein without significant difference.
Second analysis
Volatile compounds by compound class
Number of volatile compounds identified per subclass across all groups (results text on Figure 4A); by quantity, heterocycles dominated.
Results
What the study measured
Lactose, dry matter and solids-not-fat were significantly lower in group M3 (soybean to linseed oil 2:3) than in the other groups (lactose 6.15 % compared with 6.57–6.80 %), whereas milk urea (15.20 compared with 12.68–13.22) and polyunsaturated fatty acids (0.30 % compared with 0.20–0.25 %) were higher. Fat (0.12–0.19 %) and protein (1.28–1.52 %) did not differ significantly.
1167 lipids from 20 subclasses were recorded in the milk, including 638 triglycerides, 129 diglycerides, 93 phosphatidylcholines and 82 phosphatidylethanolamines. By relative amount, triglycerides made up around 94 % in all groups (93.88–94.48 %, no significant difference).
64 lipids differed between the groups, mostly triglycerides (47). In the OPLS-DA model, M1 in particular separated from the other groups. Among the lipid subclasses, only the diacyl hexosyl lipids (AcHex) differed significantly, with the highest value in M3 (0.089 % compared with 0.046 % in M1).
The differing lipids were assigned to 16 KEGG pathways, six of them significantly enriched, including glycerophospholipid, linoleic acid, glycerolipid and α-linolenic acid metabolism. According to the discussion, TG (18:3_10:1_18:3) rose with a higher linseed oil share.
Of 406 volatile compounds from 15 subclasses, 89 differed between the groups, mainly heterocycles (18), hydrocarbons (14) and alcohols (14). Several compound classes, including heterocycles, ketones, hydrocarbons and aldehydes, were higher in group M1 with the highest soybean oil share.
Using database matching, the authors assigned mainly fruity, oily, grassy and sweet odour notes to the differing volatile compounds (10 compounds each fruity, oily and grassy); no sensory test of the milk was carried out.
Authors’ conclusion: In the view of Ren et al. (2026), the ratio of soybean to linseed oil in the feed changed the lipid and aroma compound profile of donkey milk; of 1167 lipids and 406 volatile compounds, 64 and 89 respectively differed between the groups. The authors considered a ratio of 2:3 to be most suitable for improving lipid quality and achieving a milder aroma profile. This assessment can be followed only to a limited extent from the data presented; effects in humans were not examined.
Critical assessment
Strengths and limitations
Small groups, short periodClear limitation
Seven animals from one farm were sampled once per group after four weeks; baseline values and a group without added oil are missing. The oil share was only 0.2–0.8 % per type of oil, and the fatty acids in the feed differed between the groups only partly in a stepwise manner.
Text contradicts tablesNote
The discussion describes a significant increase in lactose and dry matter in M4 and unchanged urea; according to Table 2, lactose and dry matter were lower in M3 and urea higher in M3 (p = 0.044), while M4 did not differ from M1 and M2. Likewise, the text says AcHex was higher in M1 and M2, while Table 3 shows the highest value in M3.
Milk fatty acids not shownNote
The abstract reports an increase in C18:3 with increasing linseed oil share. However, individual fatty acids are reported only for the feed; for the milk, only the sum of polyunsaturated fatty acids is given, and this did not rise stepwise (M3 0.30 %, M4 0.25 %).
Counts and unitsNote
The broken-down classes of the 64 differing lipids add up to 63, those of the 89 volatile compounds to 87. The stated triglyceride share of 55.09 % does not exactly match 638 of 1167 lipids (54.67 %). Units are missing for urea and freezing point depression.
Assessment not derivedNote
The conclusion that the 2:3 ratio improved lipid quality the most is not justified by defined criteria; at the same time, M3 had the lowest lactose and dry matter values. Odour notes are based on database assignments, not on a tasting. The study uses the same ethics approval number as other papers by the group with a different trial design.
Graded feeding designStrength
Four graded oil ratios with an otherwise identical basal ration, a fatty acid and lipid analysis of the feed and the combination of lipidomics and GC-MS provide a broad picture. The OPLS-DA model of the volatile compounds was checked with a permutation test (Q² = 0.853).
Editorial assessment: The study shows that even small shares of oil in the feed of jennies can be reflected in the lipid and aroma compound profiles of the milk. Because of small groups, the lack of a control group and several contradictions between text and tables, the results should be understood as indications; no statements about taste, effects or individual commercial products can be derived from them. To the research archive.
Research question for DON DONKEY’S®
Can feed-related shifts in individual fatty acids such as α-linolenic acid in donkey milk be confirmed with complete fatty acid profiles of the milk, baseline measurements and a group without added oil over a longer lactation period, and are the differences in the aroma compound profile perceptible to the senses?
Original publication
Impact of dietary soybean and linseed oils on the lipid and volatile compound profiles of donkey milk
Original title of the publication.
Ren W., Sun L., Du X., Meng L., Khan M.Z., Wang C., Li M.
Food Science of Animal Resources · 2026 · 46(1), 27
School of Agriculture and Biology, Liaocheng Research Institute of Donkey High-Efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China; Key Laboratory of Quality Safety Control for Milk and Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, China
10.1007/s44463-025-00009-w: 10.1007/s44463-025-00009-w
Transparency: National Key R&D Program of China (2022YFD1600103, 2023YFD1302004), Shandong Provincial Natural Science Foundation (ZR2022QC130), Shandong Province Modern Agricultural Technology System Donkey Industrial Innovation Team (SDAIT-27), Support Program for Innovation and Technology in Universities of Shandong Province (2023KJ354), Livestock and Poultry Breeds Project of Ministry of Agriculture and Rural Affairs (19211162), Key Technology Research and Development Program of Shandong (2021TZXD012) and Innovation and Entrepreneurship Training Program for College Students (CXCY2024270). The authors declare no potential 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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