Milk and dairy products are an integral nutrient in the human diet. In particular, it is cow’s milk. With the increase in the production of dairy products, the growing consumption of these products has contributed to an increase in health problems associated with the occurrence of allergies and intolerances. This is related to the composition of milk, which contains proteins, mainly caseins. Particular attention should be paid to β-caseins.
There are many genetic variants of β-casein (CSN2), but the most common are A1 and A2. The difference between them is a single amino acid change in the protein chain. The consequence of this change is the effect of the formed protein on the body. Studies have shown that consuming milk containing only β-casein A1 exacerbates gastrointestinal problems compared to milk formulated with β-casein A2, the use of which in the diet can lead to a reduction in lactose intolerance and milk protein allergies.
It is therefore advantageous to breed species that produce β-casein A2, both in terms of protein content and positive effects on human health. This gene, due to its codominant nature, enforces a preference for homozygous individuals. This is due to the fact that only organisms with A2A2 alleles in the genotype are able to produce milk containing only A2 protein.
The occurrence of beta-casein A2 polymorphism has been demonstrated in different breeds of cattle: Lineback, Devon, Ankole-Watusi, Ayrshire, Beefmaster, Belgian Blue, Brown Swiss, Dexter, Dutch Belted, Gir, Guernsey, Holstein-Friesian, Jersey, Kerry, Maine-Anjou, Miniature Zebu, Montbeliarde, Normande, Norwegian Red, Piedmontese, Pinzgauer, Red & White, Salers, Shorthorn, Simmental.
| Result | Interpretation |
| A1A1 | MILK ONLY WITH BETA-CASEIN A1 |
| A1A2 | MILK WITH BETA-CASEIN A1 AND A2 |
| A2A2 | MILK ONLY WITH BETA-CASEIN A2 |
REFERENCES #
- Kamiński S., Ruść A. & Cieślińska A. (2006). A note on frequency of A1 and A2 variants of bovine beta-casein locus in Polish Holstein bulls. Journal of Animal and Feed Sciences, 15(2), 195-198.
- Olenski K., Kamiński S., Szyda J. & Cieslinska A. (2010). Polymorphism of the beta-casein gene and its associations with breeding value for production traits of Holstein–Friesian bulls. Livestock Science, Volume 131, Issue 1, 137-140.
- Radkowska I. (2020). Identification and health-promoting properties of milk containing A2 β-casein. Rocz. Nauk. Zoot., Vol. 47, No. 2, 165–177.