Saving Time and Money with bActivate: A Smarter Approach to Endometritis in Mares

For many horse breeders, a mare that repeatedly fails to conceive represents a significant financial and emotional burden. A single breeding season at a warmblood or thoroughbred stud can cost thousands of euros in covering fees, veterinary examinations, pregnancy testing and housing. When that investment yields a barren mare, the pressure to diagnose and solve the problem quickly is intense.

The standard diagnostic pathway, uterine swab, culture, antibiotics, sounds straightforward. In practice, it frequently fails because the most common cause of chronic mare infertility, dormant Streptococcus zooepidemicus, is invisible to standard culture techniques and resistant to antibiotic treatment in its dormant state.

The Hidden Cost of Missed Diagnosis

Consider a typical scenario: a mare returns a culture-negative swab. The veterinarian, seeing no bacteria, clears her for breeding. She is covered, fails to hold a pregnancy, and the cycle repeats. By the end of the season, the breeder has paid for:

• Multiple covering fees (often €1,000-5,000+ per attempt in warmblood breeding)
• Repeated veterinary examinations and ultrasounds
• Antibiotic courses that provide temporary improvement but no lasting resolution
• A lost season, the mare produces no foal, no income, no genetic progress

Research indicates that 70-80% of mares that remain open at the end of the breeding season are chronically infected with dormant bacteria. This is not a rare edge case, it is the most likely explanation for a mare that cycles normally but fails to get in foal.

Why the Standard Approach Is Expensive by Design

The problem with treating endometritis using the conventional detect-and-treat approach is that it targets only the bacteria that are already active and detectable. Dormant persister cells, the subpopulation embedded deep in the endometrial mucosa, survive antibiotic treatment, repopulate during the next oestrus cycle, and trigger another round of inflammation.

This creates a pattern of apparent short-term success (fluid clears, swab goes negative) followed by renewed infertility. The breeder invests in another season. The cycle continues.

Prof. Anders Miki Bojesen, Professor of Veterinary Microbiology at the University of Copenhagen, has described this mechanism in peer-reviewed research: dormant streptococcal cells form biofilm-protected colonies within the uterine mucosa that are not reached by systemic or intrauterine antibiotics at standard doses.

The Economic Case for Activate-First

The bActivate protocol introduces a single diagnostic step before antibiotic treatment: reactivation. A veterinarian instils 10 ml of bActivate into the uterus during early oestrus. Within 48 hours, dormant bacteria wake up, begin multiplying, and become detectable by standard culture. The culture result now reflects the actual infection, not just the fraction of bacteria that happened to be active on the day of the swab.

This changes the economics of treatment fundamentally:

• One diagnostic step replaces multiple inconclusive swabs
• Targeted antibiotic treatment based on a real culture result is more effective than empirical broad-spectrum therapy
• Treatment in one cycle followed by breeding in the next cycle
• 83% pregnancy rate in problem mares at Hagyard Equine Medical Institute (64 mares, Dr. Kristina Lu)
• 89% pregnancy rate at Kildangan/Godolphin Stud in Ireland (19 thoroughbred mares)

For a mare that has been barren for two or three seasons, a single bActivate treatment cycle costing a fraction of a covering fee is a straightforward economic decision.

How to Use bActivate in Your Breeding Programme

bActivate is a prescription veterinary product. Your veterinarian will assess whether your mare is a suitable candidate based on her reproductive history. The protocol is performed during a normal oestrus cycle approximately one cycle before the intended breeding.

Mares most likely to benefit include those with:

• Repeated failure to conceive despite normal cycles
• Culture-negative swabs combined with unexplained infertility
• A history of recurrent uterine fluid on ultrasound
• Previous antibiotic treatment without lasting improvement
• Multiple barren seasons in mares aged 8 years or older

If your mare fits this profile, read more about when bActivate is indicated or find your nearest bActivate distributor.

Frequently asked questions

How much does bActivate cost?
EUR 229 per vial, with one vial used per activation cycle, plus your veterinarian's normal fees for the instillation and the two cultures. Set against one covering fee or one lost season, the diagnostic step is the smallest number in the calculation.

Is it worth testing a problem mare before another breeding season?
An estimated 70 to 80% of mares still open at the end of a season carry a hidden uterine infection that standard culture misses. Testing first replaces a repeat of last season with a diagnosis, and the whole protocol fits inside one oestrus cycle.

How much time does the bActivate protocol take?
One cycle. Activation and the second culture take 48 hours, treatment follows the culture result and is completed no later than three days after ovulation, and the mare is bred on the following cycle.

Can I skip the diagnostics and just treat with antibiotics?
That is the expensive route. Blind antibiotic courses fail on dormant bacteria, clear the surface signs, and hand you the same problem next season. Identifying the bacteria first is what makes the treatment targeted and final.

Written by the Bojesen & Petersen Biotech ApS team. Medical oversight: Prof. Anders Miki Bojesen DVM PhD (University of Copenhagen) and Dr. Morten Rønn Petersen DVM PhD Dipl. ACT (Rigshospitalet).