Donkey Milk Study: Milk Fat and Lipid Profiles of Blood and Milk (Zhang 2026)

Twelve jennies with the same diet were grouped by milk fat (0.42% vs. 0.13%). In the blood, only 11 lipids differed, while 131 differed in the milk—mainly triglycerides.

The study in brief

• Original title: Quantitative lipidomic analysis of blood and milk in jennies with high and low milk fat content
• Authors: Zhang L.-T., Zhang K., Yan Q.-X. et al.
• Journal: Veterinary and Animal Science, 32, 100607 (2026)
• Country: China · Study type: Animal study

How the study was conducted

Twelve non-pregnant, lactating crossbreed jennies (Xinjiang × Dezhou, 2nd or 3rd lactation, 20–30 days in milk, averaging 7.0 years and 225 kg) received the same ration in individual pens (roughage to concentrate 6:4, approximately 3% of body weight). After 14 days, they were divided into a high milk fat group (fat content > 0.4%, fat yield > 5 g/day) and a low milk fat group (fat content < 0.2%, fat yield < 3 g/day), with six animals in each. On day 28, milk yield and milk composition were determined, and on day 29, blood plasma was collected (two blood samples per group were lost, so n = 4).

Key figures

• 12 – jennies, 6 in the high and low milk fat groups
• 0.42% vs. 0.13% – milk fat content in the high vs. low group (p = 0.004)
• 7.28 vs. 1.97 g/day – daily milk fat yield (p < 0.001)
• 1958 vs. 1475 g/day – milk yield corrected to 24 hours (not significant, p = 0.180)
• 6.66% vs. 6.70% – lactose content, no group difference
• 1.76% vs. 1.78% – protein content, no group difference

Results

The high milk fat group had 0.42% fat and 7.28 g of milk fat per day, while the low milk fat group had 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 identified, around 790 in the blood and around 500 in the milk. In the blood, glycerophospholipids made up over 50% of the lipid count, while in the milk, glycerolipids made up over 50%; triglycerides accounted for 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, predominantly glycerophospholipids, were different.

Limitations of the study

• Very small groups: Six jennies from one farm were examined in each group, but only four remained for blood lipids after sample loss. The authors themselves cite the small sample size as a limitation; the lack of differences in the blood is only limited in its significance given this group size.
• Inconsistent number of subclasses: According to the abstract, 17 lipid subclasses differed in the milk, while the results and discussion state nine—which corresponds to the count in Table 6. Furthermore, the results section mentions 44 subclasses, the discussion mentions 47, while Table 6 contains 43 rows according to the editorial count. The statement that 41 of the 44 subclasses differed between the milk groups only makes sense when comparing blood to milk.
• Measure of dispersion in Table 3 unclear: The column is labeled "SD," while the methods section states mean ± SE. The reported coefficients of variation (e.g., 44.04% for 0.42 ± 0.08% fat) only work out mathematically if the column contains the standard error.
• Interpretation of the fatty acid pattern: The authors attribute the differences to de novo synthesis in the mammary gland and emphasize that odd-chain fatty acids showed little difference. However, the key lipid with the highest content, DG 21:0_16:0, contains an odd-chain C21 fatty acid. Gene expression in the mammary gland was not measured.
• Marker candidate without numerical data: No concentrations are provided in the main text for DG 18:0_18:0, which is proposed as a possible marker for low milk fat; the data is only available in the supplementary material. The authors themselves emphasize that the marker still needs to be confirmed. The assignment of metabolic pathways mentions eight pathways but only lists seven.

Level of evidence: Animal study—describes measured values in the animals examined and their milk; no statement on effects in humans.

Our assessment

The study describes how blood and milk lipids differ in jennies with different milk fat contents under the same diet. It provides basic knowledge on milk production in animals; no conclusions can be drawn about the composition of individual commercial products or effects in humans.

Source: Zhang L.-T., Zhang K., Yan Q.-X., Deng L., Degen A., Liu L.-L., Zhou X.-L. (2026). Quantitative lipidomic analysis of blood and milk in jennies with high and low milk fat content. Veterinary and Animal Science. DOI: 10.1016/j.vas.2026.100607 · Summarized by the DON DONKEY'S editorial team, as of October 2026.

End of the study summary. The study was conducted independently by DON DONKEY'S® and does not refer to our products. Our donkey milk is a food.