23/11/2025
Phantom Cows - She’s definitely pregnant… until she turns up empty at scanning!
There are always those cows that, come scanning time, turn up empty even though they were mated early and never returned to heat. These cows are known as phantom cows—defined as cows that do not return to heat within 24 days of an unsuccessful insemination. Essentially, they’re “pretending” to be pregnant. Researchers are still working to understand the reasons why some cows behave this way.
It’s estimated that the current phantom rate in the national herd is up to 10%. We’ve found it can be around 20% in hormonally treated cows (CIDRs or DIBs). You can roughly work out your phantom rate by counting cows that had a single insemination, did not return to heat, and then turned up empty at scanning.
So, what can be done?
If reducing your empty rate and retaining valuable cows is a priority, early scanning at around 35 days post-insemination can help. This is especially useful for hormonally treated cows, which are usually mated within the first week of mating. Provided the cows haven’t been re-mated since, we can confirm which ones are empty and decide whether intervention is needed. For this to work, excellent record-keeping and heat detection are essential. We usually carry out this scanning in week 5 or 6 of mating.
If you’d like to know more about this, please talk to your vet.
