Cow's Milk Contains Natural Antimicrobial Peptides That Vary by Breed and Farming Method | Research

The takeaway

Proteomics analysis of cow's milk from different breeds revealed varying levels of antimicrobial peptides (cathelicidins and annexins) and antibiotic resistance proteins, with intensive farming breeds showing higher AMP levels.

98.4% breed classification accuracy
Machine learning analysis of milk protein profiles could distinguish traditional Podolica breed milk from intensive-farming breed milk with 98.4% accuracy, demonstrating that protein composition — including antimicrobial peptide levels — varies meaningfully by breed.

What the researchers found

Analysis of bovine milk using advanced proteomics revealed:

- Approximately 220 bovine proteins were quantified across breeds

- Cathelicidins (antimicrobial peptides) and annexins showed higher abundance in intensive-farming breeds compared to Podolica (traditional pasture breeds)

- Machine learning (LAP-MALDI MS with LDA) could distinguish Podolica milk from other breeds with 98.4% accuracy in the test set

- Antibiotic resistance proteins (beta-lactamases and tetracycline resistance proteins) were detected in milk from all breeds, with no significant breed-specific differences

- Metaproteomics revealed diverse microbial ecosystems in milk that varied with environmental factors

Why it matters

Understanding the natural antimicrobial peptide content of milk is important for food safety and for identifying new potential antimicrobial compounds. The finding that antibiotic resistance proteins are present in raw milk from all breeds — regardless of farming intensity — has implications for food safety and the spread of antibiotic resistance. Additionally, cathelicidins from milk are studied as potential templates for new anti-infective agents.

How the study worked

Milk samples from four bovine breeds (three intensive-farming and one traditional) were analyzed using three complementary approaches: LAP-MALDI mass spectrometry profiling with machine learning classification, bottom-up proteomics (using the Bos taurus database to identify bovine proteins), and metaproteomics (to characterize the microbial community). Antibiotic resistance proteins were identified using the Comprehensive Antibiotic Resistance Database (CARD).

What this study cannot tell us

The study examined raw (unpasteurized) milk, which is not representative of commercially consumed milk in most countries. Sample sizes per breed are not specified in the abstract. The higher cathelicidin levels in intensive-farming breeds could reflect breed genetics, farming conditions, or subclinical mastitis rather than breed-specific biology. The clinical significance of detecting antibiotic resistance proteins in milk is unclear. The study does not assess the functional antimicrobial activity of the detected peptides.

How to read the evidence

This is an analytical laboratory study using advanced proteomics techniques on bovine milk samples. While it provides detailed protein characterization data, it does not address functional antimicrobial activity or clinical relevance. It represents early-stage food science research.

When this study was published

Published in 2024, this study is recent and uses state-of-the-art proteomics techniques to characterize milk's antimicrobial peptide content, contributing to the growing field of food-derived bioactive peptides.

The bigger picture

As antibiotic resistance grows, natural antimicrobial peptides in food sources like milk are gaining attention both as protective agents and as templates for drug development. Cathelicidins — found here at higher levels in intensively farmed breeds — are one of the most studied families of antimicrobial peptides and have inspired synthetic drug candidates. Meanwhile, the detection of antibiotic resistance genes in milk from all farming types highlights the pervasive spread of resistance in the food supply chain.

Questions still open

Do the higher cathelicidin levels in intensive-farming breeds reflect a genetic trait, a response to more frequent bacterial exposure, or subclinical mastitis?
Could milk-derived cathelicidins be developed as food-grade antimicrobial preservatives or therapeutic peptides?
Does the presence of antibiotic resistance proteins in raw milk pose a risk to consumers or contribute to resistance spread?

Common questions

Does cow's milk contain natural antibiotics?

Yes — cow's milk naturally contains antimicrobial peptides, particularly cathelicidins and annexins, which are part of the cow's innate immune system. This study found that their levels vary by breed, with intensively farmed breeds showing higher concentrations. These peptides are different from antibiotic drugs added to milk (which is regulated and tested for) — they are naturally produced by the cow to help protect against udder infections.

Should I be concerned about antibiotic resistance proteins in milk?

This study detected antibiotic resistance proteins (like beta-lactamases) in raw milk from all breeds tested. However, these come from bacteria naturally present in raw milk — not from added antibiotics. Pasteurization kills bacteria in commercially sold milk, and the functional significance of these resistance proteins to human health is not established by this study. It does highlight the broader concern about antibiotic resistance spreading through agricultural environments.

Read the original research

Detection of Antimicrobial Proteins/Peptides and Bacterial Proteins Involved in Antimicrobial Resistance in Raw Cow's Milk from Different Breeds.

Antibiotics (Basel, Switzerland), 13(9)

View on PubMed ↗Publisher’s paper ↗

Citation

Piras, Cristian; De Fazio, Rosario; Di Francesco, Antonella; Oppedisano, Francesca; Spina, Anna Antonella; Cunsolo, Vincenzo; Roncada, Paola; Cramer, Rainer; Britti, Domenico. (2024). Detection of Antimicrobial Proteins/Peptides and Bacterial Proteins Involved in Antimicrobial Resistance in Raw Cow's Milk from Different Breeds.. Antibiotics (Basel, Switzerland), 13(9). https://doi.org/10.3390/antibiotics13090838