Genetic Variants in Bovine Milk Proteins

Milk from dairy cattle contains a complex ensemble of proteins, principally the casein family (α_s1, α_s2, β and κ) and the whey proteins (β-lactoglobulin and α-lactalbumin), each encoded by distinct loci and exhibiting multiple allelic variants. These polymorphisms arise through single nucleotide substitutions or small insertions and deletions, giving rise to protein isoforms such as A1, A2 and B variants of β-casein, or different κ-casein haplotypes. The distribution of these alleles varies markedly among breeds and geographical regions, reflecting historical selection for milk yield, processing performance and consumer preferences. Functionally, casein variants influence curd formation, gel strength, heat stability and foaming, while β-casein polymorphisms have been implicated in differential release of bioactive peptides during digestion. Of particular interest are peptides derived from A1 β-casein that may interact with opioid receptors, compared with the A2 variant which is often promoted for improved digestibility and reduced gastrointestinal discomfort. Advances in high-throughput genotyping and proteomics have enabled precise characterisation of variant frequencies within herds, facilitating targeted breeding strategies. Beyond technological traits, emerging evidence suggests that milk protein genotypes may modulate human health outcomes, the gut–brain axis and antioxidant capacity. Together, these findings underscore the global significance of bovine milk protein genetics, both for dairy industry optimisation and potential nutritional benefits.

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Genetic Variants in Bovine Milk Proteins publication trend

The graph below shows the total number of articles in genetic variants in bovine milk proteins across all publications each year (not limited to Nature Index journals).

Technical terms

Allelic variant: A specific form of a gene at a particular locus, differing by one or more nucleotides.

Casein: Group of phosphoproteins (α_s1, α_s2, β, κ) that form micelles and are the major protein fraction in milk.

β-Lactoglobulin: A major whey protein in bovine milk, existing in genetic variants that affect heat stability and allergenicity.

Haplotype: A set of DNA variations or polymorphisms that tend to be inherited together within a genomic region.

Polymorphism: The occurrence of two or more alleles at a locus in a population, leading to genetic diversity.

Single nucleotide polymorphism (SNP): A variation at a single base position in the genome among individuals.

Bioactive peptide: A peptide released during digestion that exerts physiological functions beyond basic nutrition.

Rennet coagulation: The enzymatic process by which casein micelles aggregate, forming curd in cheese-making.

References

1. Effect of Protein Genotypes on Physicochemical Properties and Protein Functionality of Bovine Milk: A Review. Foods (2021).
2. Frequencies Evaluation of β-Casein Gene Polymorphisms in Dairy Cows Reared in Central Italy. Animals (2020).
3. The β-casein (CSN2) A2 allelic variant alters milk protein profile and slightly worsens coagulation properties in Holstein cows. Journal of Dairy Science (2022).
4. Systematic Review of the Gastrointestinal Effects of A1 Compared with A2 β-Casein. Advances in Nutrition (2017).
5. Effects of Different Cow-Milk Beta-Caseins on the Gut–Brain Axis: A Narrative Review of Preclinical, Animal, and Human Studies. Nutrition Reviews (2024).
6. Clinical evaluation of glutathione concentrations after consumption of milk containing different subtypes of β-casein: results from a randomized, cross-over clinical trial. Nutrition Journal (2015).