- Milk production correlates negatively with plasma levels of pregnancy-associated glycoprotein (PAG) during the early fetal period in high producing dairy cows with live fetuses. L??pez-Gatius, F., Garbayo, J.M., Santolaria, P., Y??niz, J., Ayad, A., de Sousa, N.M., Beckers, J.F. Domest. Anim. Endocrinol. (2007)