Donkey Milk Study: Mannan-Oligosaccharides in Mare Feed (Li 2026)

16 lactating Dezhou donkeys received feed with or without 0.5 g/kg mannan oligosaccharides for 60 days. Milk fat (0.65 vs. 0.87%) and milk protein (1.69 vs. 1.79%) did not differ significantly; the foals tended to gain more weight (25.63 vs. 31.75 kg).

The study in brief

• Original title: Dietary Mannan Oligosaccharide Supplementation During Gestation Alters Milk Composition in Jennies and Improves Growth Performance, Lipid Metabolism, and Gut Microbiota in Dezhou Donkey Foals
• Authors: Li H., Luo J., Wen Z. et al.
• Journal: Microorganisms, 14(10), 2409 (2026)
• Country: China · Study type: Animal study

How it was investigated

Sixteen lactating Dezhou donkeys (2–3 years, 269.88 ± 31.84 kg) and their foals were randomly assigned to two groups at a breeding farm in Shandong Province (China) after three days of acclimatization (eight jenny-foal pairs per group). The control group received the farm's standard basic ration, while the experimental group received the same ration with 0.5 g/kg dry matter of mannan oligosaccharide (MOS, a prebiotic derived from yeast cell walls) mixed into the concentrate feed. The trial lasted 60 days; the foals nursed freely from the jennies.

Key figures

• 16 – lactating Dezhou donkeys with foals (8 per group)
• 0.5 g/kg – mannan oligosaccharide in the dry matter, for 60 days
• 0.65 vs. 0.87% – milk fat control vs. MOS group (p = 0.134, not significant)
• 1.69 vs. 1.79% – milk protein control vs. MOS group (p = 0.157, not significant)
• 6.95 vs. 6.85% – lactose control vs. MOS group (p = 0.224)
• 20.26 vs. 21.55 mg/dL – milk urea nitrogen control vs. MOS group (p = 0.474)

Results

The milk composition did not differ significantly between the groups. Milk fat was calculated at 0.87% in the MOS group compared to 0.65% (p = 0.134), milk protein at 1.79% compared to 1.69% (p = 0.157); the authors quantify this as a numerical increase of 33.85% and 5.92%, respectively.

Lactose (6.95% vs. 6.85%, p = 0.224) and milk urea nitrogen (20.26 vs. 21.55 mg/dL, p = 0.474) also showed no significant difference.

The foals started at comparable weights (68.75 vs. 66.56 kg). After 60 days, the final weight did not differ significantly (94.38 vs. 98.31 kg); total weight gain (25.63 vs. 31.75 kg) and daily weight gain (0.43 vs. 0.53 kg) tended to be higher in the MOS group (p = 0.091).

Limitations of the study

• Small groups, no milk effects: Only eight jenny-foal pairs from one farm were examined in each group with a single dose over 60 days. No significant difference was found in the classic milk components; the higher fat and protein values are purely calculated.
• Title does not match the trial: The title mentions supplementation during pregnancy and improved foal development. However, according to the methods section, lactating jennies were fed for 60 days, and the foals' weight gain only reached the level of a trend (p = 0.091).
• The same animal trial as an earlier paper: The number of animals, age, weight (269.88 ± 31.84 kg), dose, duration, and approval match Wang et al. (2025, Int. J. Mol. Sci.), reporting the data of the jennies from the same trial. Both articles describe the feeding times (08/18 vs. 07/19) and housing (together with foals vs. individually) differently; in the present article, the approval numbers in the methods section and ethics statement also differ from each other.
• Milk sample barely described: Only one milk sample per jenny was analyzed; the day of lactation, time, collection, and milk volume are not stated, nor is the age of the foals. It remains unclear whether the dose refers to the dry matter of the concentrate feed or the total ration; the basic ration is only in the supplementary material.
• Interpretations not directly tested: The microbiota data are based on 16S sequencing and only describe the composition, not metabolic performance; fatty acids in the feces were not measured. A connection between milk, microbiota, and the foals' blood lipids was not statistically tested. Effects in humans were not the subject of the study.

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

Our assessment

The study is a feeding trial on jennies and their foals. For the milk itself, it shows that the tested feed supplement did not measurably change the fat, protein, and lactose content under the experimental conditions. No conclusions about commercial products or humans can be drawn from this.

Source: Li H., Luo J., Wen Z., Yin Y., Huang S., Shi D. (2026). Dietary Mannan Oligosaccharide Supplementation During Gestation Alters Milk Composition in Jennies and Improves Growth Performance, Lipid Metabolism, and Gut Microbiota in Dezhou Donkey Foals. Microorganisms. DOI: 10.3390/microorganisms14102409 · 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.