Three clinical evaluations document what bActivate reveals, and what happens when the attending veterinarian treats the revealed infection. At Hagyard Equine Medical Institute (Lexington, KY), Dr. Kristina Lu's team activated and treated 64 problem Thoroughbred mares (barren for 3 or more cycles): 83% became pregnant (53/64) and 70% achieved live foals (32/46 with known outcome) (Petersen & Bojesen, Clinical Theriogenology 2014). At Kildangan Stud in Ireland, operated by Godolphin, 89% of the bred problem mares became pregnant (16/18) and 87% delivered live foals (13/15 with known outcome) (Petersen, Rosenbrock, Osborne & Bojesen, J Equine Vet Sci 2018). The peer-reviewed laboratory study (Petersen et al., Vet Microbiol 2015) confirmed bActivate activated dormant bacteria in 64% of treated mares versus 8% in PBS controls (n=37). The studies were carried out at independent clinics and studs. The founders of bActivate are co-authors on the reporting of the results, and no placebo group was included in the two field studies.
Hidden infections. Persistent infertility. Missed opportunities. For too long, problem mares, non-pregnant mares that fail to conceive despite clean swabs, normal cycles, and confirmed stallion fertility, have faced unseen barriers to reproduction.
Studies show that 80% of these barren mares harbour hidden uterine infections that traditional tests fail to detect, making pregnancy an uphill battle.
This collection introduces a breakthrough: bActivate. By reactivating dormant Streptococcus equi subsp. zooepidemicus, the most common cause of chronic uterine infections in non-pregnant mares, bActivate uncovers what was once invisible, enabling accurate diagnosis of these elusive infections for the first time.
Supported by our studies and real-world evidence, this body of work repeatedly demonstrates the profound success of bActivate in restoring fertility in problem mares. With proven results, practical solutions, and renewed hope, this is a roadmap for transforming equine reproductive health.
Step into a future where no infection stays hidden, and no mare is left behind.
The mares in these studies are the hardest group in broodmare practice. In the Kildangan cohort the average mare was 12.7 years old and had been barren for an average of 6.3 cycles before activation. Published research on a large commercial Irish Thoroughbred stud (2,385 mares, 3,743 oestrous cycles) identifies exactly this profile, high mare age and barren, slipped or rested status, as the significant risk factors for lower pregnancy rates and higher pregnancy loss (Lane et al., Reproduction in Domestic Animals 2016).
In other words: the mares bActivate is used on are the ones the published literature expects to do worst. After activation revealed the hidden infection and the stud veterinarian treated it, 89% of the bred Kildangan mares were in foal, at an average of only 1.1 covers per mare.
How to read this: these are separate datasets, not a controlled comparison, and the field studies included no placebo group. Lane et al. is cited for the difficulty of the mare group, not for bActivate, and shares an author with the Kildangan study team. Every figure on this page is attributed to the source that reports it.
bActivate is independently referenced by the world's most respected equine veterinary publications and research institutions.
"...a (growth medium) product called bActivate, which activates dormant Streptococcus that can live within the endometrium, stimulating them to become metabolically active so we can treat them."
"Infusion of Bactivate when the mare is in estrus activates the dormant B.strep, increasing replication and growth, providing identification at 24 hours."
"Most of the mares (83%) became pregnant within 6 weeks, and a majority of those gave birth to live foals.", Study of 64 broodmares treated with bActivate.
"72% of problem mares achieved live foals the year after activation. 84% of participating mares had a latent streptococcal infection."
"Knap 10% af hopperne bliver aldrig drægtige trods dyrlægehjælp. Bactivate vækker sovende bakterier, så de kan diagnosticeres og behandles effektivt med antibiotika."
"bActivate, a growth medium specifically formulated to reactivate dormant Strep uterine infections, demonstrated effectiveness: bActivate-treated mares showed 64% bacterial activation versus only 8% in PBS controls."
A veterinary thesis project by Emilie Kähler Hjenner and Kathrine Kjeldsen Ravn at the University of Copenhagen, supervised by Prof. Anders Miki Bojesen, with Prof. Henrik Elvang Jensen (pathology) and Mette Christoffersen (equine reproduction) as co-supervisors. Submitted December 2025.
Standard culture had cleared these mares. They had been barren for one to three years regardless. So the question was not how common the infection is, but a narrower one: if the organism is suspected despite a clean culture, can it be shown to be physically present in the tissue? Sixteen archived endometrial biopsies were re-examined by fluorescence in situ hybridization. Streptococcus spp. were found in all 16.
FISH binds bacterial ribosomal RNA directly in fixed tissue, so it shows the organism whether or not it will grow on a plate, and it shows where in the endometrium it is sitting.
What they found
What it confirms
The suspicion was correct. The organism is present in tissue that cultures clean, and it sits below the depth a guarded swab reaches. That is why the swab fails. It is a question of geometry, not of test sensitivity.
It also confirms the sequence. FISH can see the bacteria but cannot treat them: dormant organisms stay antibiotic-tolerant until something wakes them. The two mares that could not be activated make the point. The infection was visible under FISH, it was never made treatable, and they stayed barren.
What it does not show
The authors set out to test whether the bacteria sit in areas of chronic degenerative change. They found this in only 2 of 13, and state plainly that they cannot say whether chronic infection drives endometrosis. Endometrosis behaved as a separate and irreversible problem: the higher the Kenney score, the poorer the outcome even once the infection was cleared.
Disclosure: an unpublished student thesis project, not peer-reviewed, supervised by one of the developers of bActivate. All 16 biopsies came from mares already selected as subfertile, and no healthy control mares were examined, so the work describes what is present in problem mares rather than how common it is generally. The authors note that routine diagnostic use of FISH would first require better knowledge of the normal uterine microbiome, to avoid overdiagnosis.
A clinical study at Hagyard Equine Medical Institute (Lexington, KY) led by Dr. Kristina Lu, reported by Petersen & Bojesen at the Society for Theriogenology Annual Conference 2014 (Clinical Theriogenology 6(3):313-314). A total of 64 Thoroughbred problem mares (barren ≥3 consecutive cycles) were included and subsequently bred.
Disclosure: As no placebo group was included in this clinical study, it is not possible to determine whether fertility was significantly increased following activation and treatment solely due to bActivate. The authors disclose this limitation in the proceedings.
This field study investigates the impact of latent infections caused by Streptococcus equi subsp. zooepidemicus on fertility in mares. Dormant bacteria are shown to persist intracellularly within the uterus, evading detection by traditional methods. These infections disrupt the establishment and maintenance of pregnancy, which is why an activation step is needed before standard culture can find them. bActivate reveals the dormant infection so the stud veterinarian can treat it with targeted antibiotics.
Conclusion
Latent infections significantly reduce fertility in mares, with dormant bacteria negatively affecting pregnancy outcomes. Activation dramatically improves diagnostic accuracy, and the veterinarian's targeted treatment restores reproductive performance. Published as a congress abstract: Petersen MR, Rosenbrock A, Osborne M, Bojesen AM, J Equine Vet Sci 2018;66:117. Also written up for breeders by the founders at SelectBreeders Services (2019).
This study explores how Streptococcus equi subsp. zooepidemicus invades and survives within epithelial cells, contributing to latent endometritis in mares. The research, led by Associate Professor Bolette Skive and Professor Manfred Rohde, reveals three distinct bacterial invasion mechanisms.
This study examines antimicrobial tolerance in beta-hemolytic streptococci (BHS) from problem mares, highlighting persister cells that tolerate penicillin at 10,000 times the normal MIC. Using bActivate, dormant BHS were reactivated and successfully treated.
This document provides scientific and practical evidence supporting the use of bActivate for diagnosing and treating latent endometritis in problem mares. The study highlights the reactivation of dormant Streptococcus equi subsp. zooepidemicus infections.