Donkey Milk Study: Crude Protein in Feed and Milk Yield (Yue 2022)

For 24 Dezhou donkeys, the calculated milk yield was 3.27 and 3.41 kg/d with 14.2% and 15.3% crude protein in the feed, respectively, and 2.80 kg/d with 13.1%. The milk protein content increased slightly from 1.82 to 1.87–1.89%.

The study in brief

• Original title: Effect of Varying Dietary Crude Protein Level on Milk Production, Nutrient Digestibility, and Serum Metabolites by Lactating Donkeys
• Authors: Yue Y., Li L., Tong M. et al.
• Journal: Animals, 12(16), 2066 (2022)
• Country: China · Study type: Animal study

How it was investigated

Feeding trial at the Inner Mongolia Agricultural University experimental farm (Hohhot, China) with 24 lactating Dezhou donkeys (34 ± 4.9 days in lactation, 2.52 ± 0.72 kg/d milk, 2.8 ± 0.6 births, 239 ± 24 kg) kept individually with their foals. The animals were randomly assigned to three rations with 15.3% (high), 14.2% (medium), and 13.1% crude protein (low) in the dry matter (n = 8 each); all rations were energy-matched (12.4 MJ/kg metabolizable energy) with a concentrate-to-roughage ratio of 30:70 based on foxtail millet straw and alfalfa. After a 2-week adaptation period, followed by 8 weeks of data collection.

Important figures

• 24 – Dezhou donkeys, three groups of 8 animals each
• 13.1 / 14.2 / 15.3 % – crude protein content of the rations in the dry matter
• 12.4 MJ/kg – uniform metabolizable energy of all rations
• 10 weeks – duration of the trial (2 weeks adaptation, 8 weeks collection)
• 0.70 / 0.82 / 0.85 kg/d – actually milked milk yield (low / medium / high)
• 2.80 / 3.27 / 3.41 kg/d – calculated daily milk yield (milked amount × 4)

Results

The milked milk yield was 0.85 and 0.82 kg/d higher at 15.3% and 14.2% crude protein than at 13.1% (0.70 kg/d); calculated, this corresponded to 3.41, 3.27 and 2.80 kg/d. There was no significant difference between the high and medium levels.

The milk protein content (1.89 and 1.87 vs. 1.82%), dry matter (9.20 and 9.18 vs. 9.13%) and milk urea nitrogen (41.06 and 39.89 vs. 33.98 mg/dL) were higher in the two higher levels than in the low one. Fat (0.25–0.28%) and lactose (7.07–7.11%) remained unchanged.

Due to the higher milk yield, the daily milked amounts of protein (64.44 and 60.84 vs. 50.93 g), lactose (243.34 and 232.27 vs. 197.29 g) and dry matter (313.54 and 299.68 vs. 254.91 g) also increased.

Limitations of the study

• Small, short trial: Eight animals of one breed per group were studied at an experimental farm over eight weeks, with three closely spaced protein levels. In addition to crude protein, the proportions of corn, soybean meal, and corn gluten in the ration also changed.
• Calculated milk yield: The daily milk yield is the milked amount multiplied by the literature factor of 4. Energy- and solids-corrected milk as well as protein synthesis efficiency were calculated using formulas for dairy cows; the authors themselves acknowledge the limited applicability.
• Inconsistency between table and text: According to the text, the daily fat content was significantly higher at the high and medium levels than at the low level; however, in Table 2, the medium level (8.83 g, "ns") does not differ from the low level. The column headers in Tables 3 and 4 are "WP" and "HF/WF" instead of HP/MP, and for SCM/DMI it is "025".
• Implausible units in the serum: Calcium (2.73–2.78) and phosphorus (1.29–1.33) are given in "mg/L", not non-esterified fatty acids (0.17–0.28) in "µmol/L". At this magnitude, the values are more likely to fit mmol/L; the units are therefore not editorially verified.
• Interpretations not directly tested: The assessment that 15.3% crude protein means oversupply is based on blood and milk urea values; a nitrogen balance was not created. The health properties of donkey milk mentioned in the introduction were not the subject of the study.

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

Our assessment

The study provides data on the feeding of lactating donkeys and the resulting milk yield and basic composition. Conclusions about other breeds, housing systems, or individual commercial products cannot be directly derived from this.

Source: Yue Y., Li L., Tong M., Li S., Zhao Y., Guo X., Guo Y., Shi B., Yan S. (2022). Effect of Varying Dietary Crude Protein Level on Milk Production, Nutrient Digestibility, and Serum Metabolites by Lactating Donkeys. Animals. DOI: 10.3390/ani12162066 · 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.