07/10/2026
Mare didnāt catch?
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This is the time of year that most of our mares have settled and gone home. But there are always a few that come back open, despite no obvious cause.
Subclinical endometritis is a huge problem in mares. This basically means an infection of the uterus that does not present with symptoms.
These mares will often cycle normally, although sometimes we see mares cycle more frequently or with more intense heat behavior. They will often ovulate normally. They sometimes have fluid in their uterus but that can be a variable finding depending if their cervix is relaxed or not.
It is really important to know that ultrasound is not that useful in detecting these, nor is any kind of bloodwork! SAA and CBC will both be normal!
We always recommend a pre-breeding exam including culture, cytology and ultrasound to try to find these mares and treat them before breeding cycles are wasted.
Sometimes these mares have negative cultures (bacterial growth on a Petri dish), or trace growth of an uncommon bacteria.
Sometimes they have relatively normal cytologies (cells collected from the most superficial layer of the uterus look normal under a microscope).
Generally speaking, at least one of these tests will show an issue and it is important they are used together.
In cases that mares donāt catch and we donāt have a good reason, we often repeat the culture and cytology after an infusion of acetylcystiene (or occasionally misoprostol if we believe that there may be issues with the oviducts being clear).
It is relatively common to find a hidden infection trapped in biofilm after this type of treatment and allow us to use both a biofilm reducing medication (DMSO, Hydrogen Peroxide, Acetylcystiene, TrizEDTA, etc) as well as appropriate anti-fungal or antibiotic medications depending on the culture results.
Mares that stay open can be extremely frustrating but with the right information, there is often a lot we can do to help!!
Pictures below:
1) Dr Dobsonās mare missed on her first breeding (after she skipped the pre-breeding exam), and has since cultured 4+ yeast infection. Sheās being treated with hydrogen peroxide and fluconazole and we look forward to her upcoming embryo transfer baby! Look at that yellow fluid coming out of her uterus! That is not p*e!
2) Positive culture on a seemingly normal mare who was being considered as an embryo recipient. Needless to say she did not join our herd and is being sold as a potential riding horse!
3) Neutrophils (inflammatory white blood cells, circled) on a mare that did not catch, but nothing was identified on culture. The mare was given an infusion of platelet poor plasma to help settle inflammation and her v***a seal was repaired using a Caslickās surgery. This is an older picture and since that time, she settled and is expecting a fabulous early April barrel racing prospect foal!
Questions- shoot us a message and text/give us a call! Happy to help in any way we can.
āļø (204) 436-2330
