I own a few Shire mares and have experienced first hand how erratic their cycles and follicle development can be. In 2009 I decided to try P&E with one of the mares with great success. On day 16 she had a 38 follicle, day 20 it was 50 so we inseminated that day and again the next day after which she ovulated and became pregnant. In 2010 she foaled in late June and refused to come into heat while nursing, so she was not bred that year. This spring I tried to track her cycles by watching her interaction with my stallion, but they seemed irregular so I decided to use P&E again. Gave shots for 10 days (using 1.5 dose as recommended for her size)with 1/2 dose Estrumate on days 9 and 10. I noticed she was sweating after the final Estrumate shot on day 10, so seemed to be working. Today is day 18 and her follicle is a disappointing 22. Any suggestions on what is going on with her and what we should do at this point? Or, is there anything we can do other than track this follicle and see what happens?
First off, sweating is not an indicator that a prostaglandin is working to destroy a CL. It merely indicates that there is a contraction of the smooth muscle going on. Not that I think that particularly has anything to do with it, but just wanted to clarify the point.
Did you make absolutely sure that there was no CL on the ovary when you checked her at day 18 (today)? You need to be sure that she didn't go early on you (we always like to check at about day 14/15 to give us a base-line).
Bear in mind that although P&E is very effective, it's only about 90% effective, so that means that there's still a 10% or so failure rate.
Pretty much all you can do not is follow the follicle - but make sure that there's no CL already present too.
FWIW we've been using the single-shot P&E and the biorelease altrenogest (again a single dose) from BET Pharmacy with as good effect as the I'm-so-miserable-'cos-you're-going-to-stick-a-needle-in-me-again 10 dose treatment.
Thanks for your response. My vet didn't say anything about specifically checking for a CL, but normally she does check when things seem to be abnormal. I will ask her about that tomorrow. The reason we waited until day 18 this time is her tendency to build a size 60 (or close to it) follicle before she ovulates. And in 2009 while using P&E she didn't ovulate until the night of day 21 - or maybe early morning on day 22. Maybe I was too optimistic that she would perform very much the same this year. If this follicle stalls and never does fully mature, can we try P&E again this season? This mare is very easy going about the shots (I don't even have to halter her out in the pasture to give her a shot) but maybe a slightly different approach would be worth a try.
As long as she is cycling there is no reason why you can't use P&E (or the biorelease Altrenogest) again.
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