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Research on donkey milk · Study 101
Milk fat in jennies: blood and milk lipids
Twelve jennies on the same feeding were grouped by milk fat (0.42 % vs. 0.13 %). Only 11 lipids differed in the blood, but 131 in the milk – mainly triglycerides.
At a glance · swipe or use the arrows
The key figures
Study design
How it was studied
Twelve non-pregnant lactating crossbred jennies (Xinjiang × Dezhou, 2nd or 3rd lactation, 20–30 days in lactation, on average 7.0 years and 225 kg) received the same ration in individual stalls (forage to concentrate 6:4, about 3 % of body weight). After 14 days they were divided by milk fat content and milk fat yield into a high milk fat group (> 0.4 %, > 5 g/day) and a low milk fat group (< 0.2 %, < 3 g/day) of six animals each. Milk yield and milk composition were determined on day 28, and blood plasma was collected on day 29 (two blood samples per group were lost, hence n = 4). Blood and milk lipids were quantified by liquid chromatography–tandem mass spectrometry with internal standards (nmol/mL) and evaluated with PCA, OPLS-DA, t-tests and KEGG analyses.
Interactive chart · values from the study
Lipid classes in the milk: high vs. low milk fat
Means (n = 6) from Table 6 of the study. Glycerolipids (p = 0.044), sterol lipids (p = 0.035) and sphingolipids (p = 0.048) differed significantly.
Second analysis
Selected triglycerides in the milk
The six triglycerides with the highest contents among the 26 key lipids (Table 7). The diglyceride DG 21:0_16:0 (548.5 vs. 92.4 nmol/mL) is not shown.
Results
What the study measured
The high milk fat group had 0.42 % fat and 7.28 g of milk fat per day, the low milk fat group 0.13 % and 1.97 g. Milk yield (1958 vs. 1475 g/day), lactose (6.66 vs. 6.70 %), protein (1.76 vs. 1.78 %), density and pH did not differ; body weight and feed intake were also comparable.
In total, 935 lipid species from five classes were recorded, around 790 in the blood and around 500 in the milk. In the blood, glycerophospholipids made up over 50 % of the number of lipids, in the milk glycerolipids over 50 %; triglycerides made up 48.5–49.2 % of the species in the milk and 24.6–24.8 % in the blood.
In the blood, neither total lipids nor individual lipid classes or subclasses differed between the groups; only 11 individual lipids, mostly glycerophospholipids, were different.
In the milk of the high milk fat group, total lipids (10,800 vs. 3823 nmol/mL) as well as glycerolipids, sphingolipids and sterol lipids were higher. According to Table 6, nine subclasses differed, including triglycerides (7765 vs. 1115 nmol/mL) and diglycerides (903 vs. 530 nmol/mL).
131 individual milk lipids differed, 126 of them higher in the high milk fat group; 78 were triglycerides. After stricter selection, 26 key lipids (25 triglycerides, 1 diglyceride) remained with 4- to 13-fold higher contents; the triglycerides contained even-chain fatty acids from C8 to C18, mainly C16 and C18.
Among the five lipids lower in the high milk fat group, the authors highlighted the diglyceride DG 18:0_18:0 (1,2-distearoyl-sn-glycerol). They assigned the differing milk lipids to eight KEGG metabolic pathways, including cholesterol and glycerolipid metabolism, regulation of lipolysis, and fat digestion and absorption.
Authors’ conclusion: In the view of Zhang et al. (2026), the milk fat content of jennies cannot be predicted from the blood lipid profile; in their view, the differences between jennies with high and low milk fat were mainly due to fat synthesis in the mammary gland and mainly concerned triglycerides with C16 and C18 fatty acids. They saw DG 18:0_18:0 as a possible marker still to be tested; for breeding they recommended research on genes of milk fat synthesis.
Critical assessment
Strengths and limitations
Six jennies from one farm were examined per group, and only four for blood lipids after sample loss. The authors themselves named the small sample as a limitation; the finding that the blood showed hardly any differences has limited informative value with this group size.
According to the abstract, 17 lipid subclasses differed in the milk; according to the results and discussion, nine – which matches the count in Table 6. In addition, the results section mentions 44 subclasses and the discussion 47, while by our editorial count Table 6 contains 43 rows. The sentence that 41 of 44 subclasses differed between the milk groups only fits the comparison of blood against milk.
The column is labelled “SD”, while the methods section gives mean ± SE. The coefficients of variation given (e.g. 44.04 % for 0.42 ± 0.08 % fat) only add up if the column contains the standard error.
The authors attributed the differences to de novo synthesis in the mammary gland and stressed that odd-chain fatty acids hardly differed. The key lipid with the highest content, DG 21:0_16:0, however, contains an odd-chain C21 fatty acid. Gene expression in the mammary gland was not measured.
For DG 18:0_18:0, proposed as a possible marker for low milk fat, no concentrations are given in the main text; the data are only in the supplementary material. The authors themselves stress that the marker still has to be confirmed. The pathway assignment mentions eight pathways but lists only seven.
All jennies received the same ration and were of comparable age, lactation stage and body condition. The lipids were quantified with internal standards in nmol/mL, and blood and milk from the same animals were analysed in parallel.
Editorial assessment: The study describes how blood and milk lipids differ in jennies with different milk fat contents on the same feeding. It provides basic knowledge about milk formation in the animal; no conclusions about the composition of individual commercial products or effects in humans can be drawn from it. To the research archive.
Research question for DON DONKEY’S®
Can the differences in milk fat content between jennies be explained by gene variants or gene activity in the mammary gland, and do they remain stable over the whole lactation and with different feeding?
Original publication
Quantitative lipidomic analysis of blood and milk in jennies with high and low milk fat content
Original title of the publication.
Zhang L.-T., Zhang K., Yan Q.-X., Deng L., Degen A., Liu L.-L., Zhou X.-L.
Veterinary and Animal Science · 2026 · 32, 100607
College of Animal Science and Technology, Tarim University, Alar, Xinjiang, China; Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, China; College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, China; Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beer Sheva, Israel
10.1016/j.vas.2026.100607: 10.1016/j.vas.2026.100607
Transparency: National Natural Science Foundation of China (32260844), Tianshan Talent Project (2024) and Bingtuan Science and Technology Program (2026YD015, 2020CB026). The authors declare no competing financial interests or personal relationships that could have influenced the work. 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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