Enhancing Mare Fertility with bActivate: A Revolutionary Approach
Infertility in broodmares is one of the most persistent and costly problems in equine breeding. When a mare fails to conceive season after season despite normal cycles, good management, and experienced veterinary care, the frustration for breeders is significant. At Bojesen & Petersen Biotech, we have developed bActivate to address the most common hidden cause of this problem: dormant uterine infection.
The Hidden Root of Mare Infertility
Many breeders encounter the same disheartening pattern: the swab comes back clean, the veterinarian clears the mare for breeding, she accepts the stallion — and then fails to hold the pregnancy. Month after month, season after season, the result is the same.
The explanation in many of these cases is not poor management or bad luck. It is biology. Streptococcus equi subsp. zooepidemicus — the most prevalent bacterium in equine endometritis — can enter a dormant state within the endometrial tissue. In this persister state, the bacteria:
- Produce no detectable growth on standard culture swabs
- Cause no dramatic clinical signs such as discharge or fever
- Resist antibiotic treatment because they are metabolically inactive
- Reactivate during oestrus, producing low-level chronic inflammation that prevents embryo implantation
A 2024 German study of 28,887 endometrial swab samples found that 25.9% showed pathogenic bacterial growth, with beta-haemolytic streptococci accounting for nearly 80% of positive results. Research by Prof. Anders Miki Bojesen and Dr. Morten Rønn Petersen indicates that 50–75% of mares that remain open at the end of the breeding season carry such dormant infections. The problem is not rare — it is the most common undiagnosed cause of mare infertility.
The bActivate Approach to Fertility Enhancement
bActivate is a bacterial growth medium designed to do one specific thing: stimulate dormant streptococcal bacteria in the uterus to reactivate. When instilled into the uterus by a veterinarian during early oestrus, it creates conditions that push dormant persister cells back into an active, multiplying state. This reactivation has two critical consequences:
- Diagnosis becomes accurate. A culture swab taken 48 hours after bActivate administration detects the bacteria that are now active. The result reflects the real infection rather than a false negative produced by dormant cells.
- Treatment becomes effective. Active, dividing bacteria are susceptible to antibiotics. Targeted therapy applied after the activation swab can now eliminate the infection — including the cells that previously survived treatment in their dormant state.
The mare is then allowed to recover through one cycle before being bred in the following oestrus. The uterine environment, now clear of persistent infection, is prepared to support embryo implantation and early development.
Fertility Outcomes in Clinical Studies
The effectiveness of this approach has been demonstrated in field studies at leading equine facilities. At Kildangan Stud in Ireland — part of the Godolphin organisation and one of the most prestigious thoroughbred breeding operations in the world — 89% of 19 barren problem mares became pregnant after a single bActivate activation cycle. All 14 mares who carried to term delivered healthy, live foals.
At Hagyard Equine Medical Institute in Lexington, Kentucky, the world’s largest equine hospital, Dr. Kristina Lu conducted a field study across 64 problem mares. The pregnancy rate was 83%. These mares had previously failed to conceive through conventional diagnostic and treatment approaches.
For context, typical pregnancy rates in established problem mare populations using standard treatments often fall below 50%. Results of 83–89% in these populations represent a clinically meaningful improvement.
Which Mares Benefit Most
bActivate is particularly indicated for mares who show one or more of the following:
- Repeated failure to conceive over two or more breeding seasons
- Culture-negative swabs combined with unexplained infertility or uterine fluid
- A history of antibiotic treatment that temporarily resolved symptoms but did not restore fertility
- Early embryo loss (before day 15) in multiple seasons
- Age 10 or older with a history of reproductive difficulties
bActivate is a prescription veterinary product. Your veterinarian will assess suitability based on reproductive history, clinical examination and ultrasound findings.
Watch: The Science Behind Dormant Bacteria and bActivate
Prof. Anders Miki Bojesen (University of Copenhagen) explains how dormant streptococcal persister cells embed within the uterine lining, why they evade standard diagnosis and treatment, and how bActivate reactivates them.
For more information, read about how bActivate works, review the full clinical evidence, or order bActivate directly online.
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.
What our clients say
Real results from veterinarians and breeders who have used bActivate on their most challenging problem mares.
“We incorporated bActivate into our standard reproductive work-up for problem mares at Hagyard. Out of 64 mares that had failed to conceive for at least 3 cycles, 83% became pregnant following bActivate activation and targeted antibiotic treatment.”
“We used bActivate on 19 of our most persistent problem mares — horses that had been barren for over a year despite every conventional treatment we tried. 89% of them got in foal. What really opened our eyes was how many had a hidden infection.”
“We have been using bActivate on several mares — all got pregnant and most of them in first try with frozen semen!”
“bActivate is an excellent tool that allows us as reproductive vets to do our job effectively. It is both a smart and cost-effective solution in the long run.”
“I used bActivate and after just one covering got a colt foal — after 3 years of hardship where the mare went in foal but never managed to produce a live foal. I cannot recommend bActivate enough.”
“Our 18-year-old mare had failed for five consecutive seasons. After bActivate she was confirmed strongly positive for Streptococcus — an infection standard testing had completely missed. She was treated, covered in September, and for the first time in five seasons there was no fluid present at ovulation. She is now 34 days in foal. This is the first time a pregnancy has not involved invasive flushing, excessive drugs and a battle to hold it.”