In the February 2015 e-newsletter, the Dairy Cattle Reproduction Council shares that researchers at the University of Wisconsin recently conducted one of the first studies to directly compare factors associated with blood and milk pregnancy-associated glycoproteins (PAGs) levels during the first trimester of pregnancy in Holstein cows. Their findings will be published in an upcoming issue of the Journal of Dairy Science.
Results show:
- Stage of gestation, parity, pregnancy loss and milk production were associated with similar relative PAG levels in both blood and milk tests.
- Milk PAG levels were about 2-fold lower than blood PAG levels.
- Based on weekly PAG profiles in blood and milk samples, the optimal time to conduct a first pregnancy diagnosis is around 32 days after timed-artificial insemination (TAI), when blood and milk PAG levels are at an early peak.
- Conducting either the blood or milk PAG test during the low point in blood and milk PAG levels results in poor overall accuracy. The low point occurred 53 to 60 days after TAI for the plasma PAG assay and from 46 to 67 days after TAI for the milk PAG assay.
Because of pregnancy losses, all pregnant cows should be submitted for a pregnancy recheck 74 days or later after A.I.
Source:uwex.edu