Donkey Milk Study: Protein Profile and Whey Proteins (Polidori 2013)

In donkey milk from Martina Franca donkeys, lysozyme decreased from 1.34 mg/mL (day 60) to 0.76 mg/mL (day 190); β-lactoglobulin averaged 3.75 mg/mL, and lactoferrin 0.080 g/L.

The study in brief

• Original title: Use of Donkey Milk in Children with Cow's Milk Protein Allergy
• Authors: Polidori P., Vincenzetti S.
• Journal: Foods, 2(2), 151–159 (2013)
• Country: Italy · Study type: Laboratory study

How it was investigated

Laboratory work with a highly summarizing character: The protein profile of milk from 20 Martina Franca donkeys in mid-lactation from a farm in central Italy was examined. Caseins and whey proteins were separated by ion-exchange and reverse-phase chromatography, separated by SDS-PAGE, and identified by N-terminal sequencing; additionally, two-dimensional electrophoresis of total caseins was shown. Lysozyme, β-lactoglobulin, and α-lactalbumin were quantified at five points in lactation (days 60–190), lactoferrin was determined by chromatography, and lactoperoxidase by its enzymatic activity.

Important figures

• 20 – Martina Franca donkeys in mid-lactation (one farm, central Italy)
• 1.34 → 0.76 mg/mL – Lysozyme from day 60 to day 190 (Table 3)
• 1.0 mg/mL – average lysozyme content according to the text
• 3.75 mg/mL – average β-lactoglobulin (days 90–190)
• 0.81 → 1.97 mg/mL – α-lactalbumin from day 60 to day 90
• 0.080 ± 0.0035 g/L – Lactoferrin

Results

By ion-exchange chromatography and gel electrophoresis, nine peaks were separated and identified as β- and αS1-caseins. αS2-, γ-, and κ-casein were not detected in this work.

Reverse-phase chromatography of the skimmed milk revealed three main peaks: lysozyme (14.60 kDa), α-lactalbumin (14.12 kDa), and β-lactoglobulin (22.40 kDa). In the 2D electrophoresis of total caseins, around 14 spots were shown, predominantly β- and αS1-caseins, with significant heterogeneity.

Lysozyme was 1.34 mg/mL on day 60 and decreased to 0.76 mg/mL by day 190 (average according to the text 1.0 mg/mL). β-lactoglobulin was between 3.60 and 4.13 mg/mL (average 3.75 mg/mL), α-lactalbumin increased from 0.81 mg/mL (day 60) to 1.97 mg/mL (day 90) and then slightly decreased to 1.63 mg/mL.

Limitations of the study

• Title and content do not match: The title mentions children with cow's milk protein allergy, but only the protein profile of the milk was examined. The article contains no original data on tolerance in children; the classification is based on literature.
• Predominantly adopted data: Table 1 comes from literature, Tables 2 and 3 from a previous work by the same group (2008), according to the source citation, and the 2D analysis from a 2012 study. Table 4 refers to a study on human milk. What was newly measured in this article remains unclear.
• Mid-lactation or lactation course?: According to the methods section, the samples come from mid-lactation, but Table 3 shows five points from day 60 to day 190. Sample sizes per time point, measures of dispersion, and statistics are missing.
• Contradictory comparison data: The abstract mentions a casein content "very close to human milk," but Table 1 shows 0.64–1.03 versus 0.32–0.42 g/100 g for donkey milk. For lactoferrin in human milk, the text mentions 1.0–6.0 g/L, while Table 4 shows 0.3–4.2 g/L. The αS1-casein sequence in the text is RPKLPHRQPE, in Table 2 RPKLPHQPE.
• Mean value of α-lactalbumin: The abstract mentions an average α-lactalbumin content of 1.8 mg/mL. According to our own calculation, this only corresponds to the average of days 90–190; across all five time points in Table 3, it is around 1.60 mg/mL.

Level of evidence: Basic research (laboratory) – describes the properties of the milk, no statement about effects in humans.

Our assessment

The article is essentially a compilation of protein measurements of donkey milk, predominantly from previous works by the same group. It describes which caseins and whey proteins are detectable and in what quantities. Whether and how donkey milk is an option for cow's milk allergy is a medical question and is not the subject of the measurements.

Source: Polidori P., Vincenzetti S. (2013). Use of Donkey Milk in Children with Cow's Milk Protein Allergy. Foods. DOI: 10.3390/foods2020151 · 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.