For how many days post ovulation would an experienced vet. be able to see a CL when scanning a filly to see if she was coming in season. My filly ovulated and we had missed her, so she was PG'd to bring her back in season. Next scan she is not responding to the PG'ing and vet said he can see the ovulation from nearly 14 days ago. Would this be possible?
Jos Posted From: 126.96.36.199
Posted on Friday, May 21, 2004 - 08:29 pm:
The basic formation of the CL is visible about 24 hours after ovulation. Up until that time, it may be somewhat indistinct, and may present as a CH (corpus hemorrhagicum).
The CL will persist until about 12-14 days after the previous ovulation, so your veterinarian may be able to identify it still.
The most common reason for PGF2a not causing a mare to return to heat in the anticipated time frame is that there was not a fully functional CL present when the drug was administered - i.e. she was within about 6 days of a prior ovulation. Note that this could have been the previous heat cycle ovulation, or it could have been a diestrus ovulation.
If a CL is still present on ultrasound, give another dose of PGF2a, and you will be likely to get the desired effect.
Sandra KS Posted From: 188.8.131.52
Posted on Monday, June 28, 2004 - 05:59 pm:
As long as we're on this topic...how easy or difficult is it for a vet to tell the difference between a CL and a follicle using ultrasound? Is it something that would be apparent in comparing pictures with no other info, or could you only tell if you knew how long it had been since the mare ovulated and whether or not she was bred?
Jos Posted From: 184.108.40.206
Posted on Monday, June 28, 2004 - 10:44 pm:
Follicles are anechoic, or in other words the fluid contained within does not reflect the ultrasound, so they appear as black areas on the ultrasound scan.
CL's however are echoic, so they appear as various shades of grey scale, as the luteal tissue reflects the ultrasounds back to the transducer.
Very easy to differentiate.
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