---
type: condition
name: Problem Mare
description: A broodmare that has failed to conceive across three or more breeding cycles, often due to subclinical uterine infection.
also_known_as:
  - barren mare
  - non-pregnant mare
  - infertile mare
last_updated: 2026-06-13
canonical_url: https://bactivate.us/what-is-bactivate
---

# The Problem Mare

A problem mare is a broodmare that has failed to conceive across three or more
breeding cycles despite being bred to a fertile stallion. Around 35 percent of
mares remain open (not pregnant) at the end of a given breeding season, and a
significant share become repeat offenders. The historic foaling rate for
problem mares sits between 15 and 50 percent, well below the 80 to 85 percent
seen in the normal mare population. A frequent and under-diagnosed cause is
subclinical endometritis: a low-grade uterine infection that produces no
obvious clinical signs.

## Why problem mares are hard to diagnose

Between 70 and 80 percent of problem mares carry hidden uterine infections, yet
standard diagnostic swabs miss infection in more than 60 percent of cases. The
reason is that a portion of the responsible bacteria, *Streptococcus equi*
subspecies *zooepidemicus*, can persist in a dormant state inside the
endometrium. Dormant bacteria do not grow on a conventional culture plate, so
the swab reads negative and the mare is wrongly cleared of infection. The mare
keeps failing to conceive while the true cause stays invisible. This is the
diagnostic gap that the [bActivate](bactivate.md) activation medium is designed
to close.

## How the problem is addressed

Identifying the hidden infection changes the management plan. When a sample is
processed with [bActivate](bactivate.md), dormant
[Streptococcus zooepidemicus](dormant-streptococcus.md) is reactivated and
becomes detectable, allowing the veterinarian to apply a targeted antimicrobial
protocol. In the Hagyard study of 64 problem mares, this approach was associated
with a 70 percent foaling rate and an 83 percent pregnancy rate. See
[Clinical Evidence](clinical-evidence.md) for the full data.

## Related concepts

- [What bActivate Is](bactivate.md)
- [Dormant Streptococcus zooepidemicus](dormant-streptococcus.md)
- [Clinical Evidence](clinical-evidence.md)