Knowing your pregnancy rate can help you determine if your reproductive program is working correctly and what you can do to tweak it further.

A lot of producers rely on other measurements, such as average days open or first-service-conception rate. But, according to Don Niles, technical service specialist with Monsanto Dairy Business in Visalia, Calif., these measurements are not as useful as pregnancy rate.

Average days open may not alert you to a problem soon enough, or may even give you the wrong feedback. For instance, during the hot summer months, animals often have a difficult time becoming pregnant. Average days open does not alert you to this problem because it only looks at cows that have already become pregnant. While the heat stress continues, and few, if any, cows become pregnant, average days open does not change. You don’t get any feedback until after the problem is over and pregnancies start picking up again.

Conception rate only considers those cows that are still on the farm, and excludes those cows that have been culled for reproductive problems.

Pregnancy rate, on the other hand, can provide immediate feedback because it can be figured on regular 21-day intervals. It can include all animals that have been on the farm, regardless of whether they are still in the herd or not, or it can look at specific subgroups of animals.

Niles defines pregnancy rate as “the percentage of cows eligible to become pregnant in a given time frame that actually do become pregnant.” Usually, that number is figured in 21-day intervals from the end of the voluntary waiting period.