Pregnancy Testing - A key component of herd fertility made easier

With the development of new technologies, the NMR milk sample can now be used for many other tests in addition to routine quality testing - in this case using an ELISA test to detect Pregnancy Associated Glycoprotiens (PAG's) to accurately determine whether or not the cow is pregnant.

The graph below shows PAG levels throughout gestation. The blue line being the best fit between the range of samples tested. PAG levels above the dotted red line are classified as pregnant, PAG levels between the solid and dotted line are classed as re-check and PAG levels below the solid red line are not-pregnant (open). 

The test result does depend on accurate animal identification, good milk sampling technique and fertility information that is up to date, so that with the automated options, the correct samples can be selected and tested in the laboratory.

The PAG levels change as the pregnancy progresses.

From 0-60 days from calving, PAG's are still being produced by the last pregnancy - on the auto select service option cows will not be chosen for testing, if they are in this range.

From 0-35 days after the last service, the PAG level is too low to register, again, under the auto select options animals will not be picked for testing.

Between day 36 and 60 days after service the PAG level rises, but from day 60 - 80 it can drop slightly.

By 80 days after service, the PAG levels then rise continually to the next calving.
If an animal loses its calf (abortion etc), PAG's continue to be shed for some time, depending on the stage of gestation, after the event.

Where PAG levels are below 1.00, but the sample was taken after 150 days gestation, it is recommended that the animal is retested or the vet carries out a manual PD, as the animal could have lost the calf and the PAG levels are dropping to reflect this event.

Cows with a PAG level of less than 0.10 are shown as not pregnant (open), from 0.10 and 0.25 the result is inconclusive and a retest is provided, above 0.25 the result is shown as positive.

Find out why you should use Milk Pregnancy Testing