When is the best time to preg test?

When preg testing our aim is to provide accurate predicted calving dates. This allows the farmer to maximise milk yield by not drying cows off too early. Additionally, it helps to set the herd up for a good transition period. By having accurate calving dates we can move cows onto a lead feed program at the correct time. A good transition is critical to limiting metabolic disease post-calving, while also aiding fertility outcomes in the subsequent joining period.  

In order to achieve the above, we prefer to be ultrasound preg testing between 6 and 14 weeks of gestation. It is during this period that the foetus is going through a rapid growth phase. This means we can differentiate the pregnancies in week intervals. Once gestation moves beyond 16 weeks the foetus is difficult to visualise and the rapid growth phase has finished. This means the ability to accurately age the pregnancy is lost.

For most Spring herds we should be starting to preg test in late January and into February. For herds that join for longer than 10 weeks often we would carry out two preg tests, one 12 weeks after the start of AI and a follow up preg test 6-8 weeks after joining has finished. For herds with a joining of 10 weeks or less, one preg test 6 weeks after the end of joining works well.

For year round calving herds we should be preg testing at least once every eight weeks. Some year round herds elect to preg test more frequently so that animals can be moved out of the breeding group.  

It is not uncommon for cow ID, transcribing and record keeping mistakes to contribute to preg testing errors. Focusing on these areas is important in ensuring the accuracy of the preg testing data.

Accuracy of preg testing data can be further improved by allowing us access to insemination dates. This allows the matching up of preg testing and insemination dates on the day of the preg test.

Farmers should be aware that some pregnancies will be lost between preg testing and calving. As a general guide the loss of 1-2% of pregnancies during this period would be deemed normal. Due to this risk, it is a good idea to consider a dry off preg test to find these cows. Finding a small number of empty cows easily justifies the additional preg test by either keeping the cows in milk or preventing the expense of the dry period.

For clients that are interested we can also generate a fertility focus report. This looks into fertility indices such as the calving pattern, first calver milk production compared with mature cows, submission rate, conception rate, and six week in calf rate (seasonal herds) or 100 day in calf rate for year round herds. 

If you have any further questions regarding the preg testing of your herd, feel free to contact the clinic.