I had my 3 yo maiden mare ultrasounded early May to get an idea of where she was in her cycle. She had just ovulated 24-48 hours prior. Counted out and scheduled her for another ultrasound 16 days later. US showed she had just ovulated again 24-48 hours prior. So scheduled another visit 7 days later on 5/31. She had a 26mm on the right and a 23mm on the left. Scheduled another check 2 days later (yesterday 6/2) She had just ovulated the 26mm on the right and the follicle on the left was now a 25mm. She is very quiet and subtle about her signs of being in heat. No edema has really been noticed either.
Interestingly her 1/2 sister is stalled next to her and she was checked on 5/31 with a 25mm & a 21mm. We were told she was not in heat and it looked like she had a CL. She was showing clear signs of being in heat so we had her checked yesterday 6/2 anyway. She grew from a 25mm no edema on Tuesday to a 35mm with lots of edema in 2 days. Luckily we had semen and she was bred.
Any ideas or thought would be great! Is the shorter cycle genetic? Is this normal for them? Or could there be something else going on? The semen I need to order for my mare is fresh and is coming out of Canada.
Mare 1: If she truly has a 12 day inter-ovulatory period, presuming that you are not dealing with diestrus ovulations (which is a possibility that should be ruled out), you need to have a uterine swab culture and cytology performed as one of the most common reasons for a short inter-ovulatory period is a uterine infection.
Mare 2: While going from a 25 to a 35 in 2 days seems a big leap, it's not that uncommon, especially at this time of the year (the height of the breeding season). Average follicular growth is 3-5 mm a day, so as you can see, she was at the high end of normal - and if the follicle was not spherical (which is not uncommon) then she may not have been a 25/35 on the average of two measurements taken at 90° to each other (which should always be done).
Thanks Jos! Discussed everything with my vet and we will be taking another look at my mare tomorrow. Hopefully we will be able to figure out if she is having diestrus ovulations and get a culture/cytology done. If not start her on the process so we can do it.
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