Comparative Effects of Milk Containing A1 versus A2 β-Casein on Health, Growth and β-Casomorphin-7 Level in Plasma of Neonatal Dairy Calves

Beta-casomorphin-7, a peptide from milk protein, binds to mu-opioid receptors in the brain and increases food intake by activating neural reward circuits.

Neonatal dairy calves fed A2 milk for 21 days develop looser stools and more diarrhea than calves fed A1 milk, even though both groups gain the same amount of weight.

After drinking milk, newborn dairy calves have measurable levels of a seven-amino-acid peptide called β-casomorphin-7 in their blood. These levels rise by day 3 and decrease by day 21, showing that their intestines absorb this peptide during early life.

Milk with A2 β-casein contains more protein than milk with A1 β-casein, and calves drinking A2 milk grow just as well even when they drink less of it.

Neonatal dairy calves fed A2 milk for 21 days have plasma β-casomorphin-7 levels that are nearly five times lower than calves fed A1 milk, demonstrating that A2 β-casein produces less of this peptide during digestion.

Neonatal dairy calves fed A2 milk gain the same weight as those fed A1 milk, even though they drink 5% less milk, because A2 milk has more protein that may enhance how efficiently nutrients are used or how amino acids are balanced.