Milk Pregnancy Test

Milk Pregnancy Submittal Form

A highly successful and efficient reproductive management program is critical to maintaining profitability. Poor reproductive performance will lead to longer calving intervals and result in higher culling rates and lower production. A good breeding program includes timely determination of initial pregnancy followed by subsequent confirmations that a cow remains pregnant. Northwest Labs recently expanded its extensive diagnostic capabilities with the long sought after milk pregnancy test. The Northwest Labs Milk Pregnancy Test is a cost effective and labor-saving means to quickly determine if a lactating cow is pregnant or open.

The economics of pregnancy loss

Most pregnancy losses occur during early gestation. Traditional methods, such as palpation, generally take place 30-40 days after breeding, however with the introduction of ultrasound and blood-based pregnancy tests, that window has been pushed back to 26-29 days. Figure 1 shows that pregnancy losses from 28 days to 56 days into gestation can be as high as 17.2%. An additional 7.2% loss occurs from 56 to 282 days in gestation. Table 1 shows a typical cost of pregnancy loss by lactation and stage of gestation. Research by Fetrow determined that the cost of longer days open is approximately $2-$6 per cow per day. Although producers have implemented best management practices to limit pregnancy loss, it cannot be completely eliminated. When reviewing the information in Table 1 it is easy to see that determining pregnancy loss as soon as possible will limit the financial impact.

Graph 1. Pregnancy loss in lactating Holstein cows assessed using transrectal ultrasonography from Day 28 post breeding to calving. Total loss from Day 28 of gestation to calving was 24.7%. (Adapted from Vasconcelos et al., 1997)

Lactation Number

Month of Gestation
















Table 1. Cost of pregnancy loss after 1, 4, or 7 months of gestation, based on a simulation model for an average herd (Davis, University of Florida, J. Dairy Sci., Economic value of pregnancy in dairy cattle)

How does the test work?

The milk pregnancy test, is an enzyme-linked immunoassay for the detection of pregnancy-associated glycoproteins (PAGs) in bovine milk as a marker for pregnancy. The milk pregnancy test is a highly sensitive (>99%), highly specific (>97%) and highly accurate (>98%) test confirming pregnancy status from 35 days post breeding and from 60 days post calving. PAG levels (represented by S-N Values) vary by cow and also by stage of gestation. See graph below for typical behavior. PAG levels decline typically from day 29 to day 60 and thereafter climb. For this reason, Northwest Labs Milk Pregnancy Test is best used to confirm pregnancy after initial determination has been made via blood serum, palpation, or ultrasound.


Incorporating milk pregnancy confirmation as part of DHI testing

Although the producer can collect milk samples and mail into the lab at any time, the greatest cost savings are obtained if the sample is collected as part of regular DHI testing. The milk pregnancy test can be conducted using the same preserved milk sample used for milk component and somatic cell count testing.

Which cows to test?
The producer can provide a list of cows to test, or the field technician can create a list based on number of days carried calf. Figure 2 shows an example of a cost effective protocol that catches early and late gestation pregnancy losses.


Contact Brock for pricing and further information. 208-315-4721.