When to Use bActivate for Problem Mares
In short. bActivate is for the mare that stays empty despite normal cycles, a fertile stallion and a clean swab. The strongest signs are two or more failed cycles, uterine fluid on ultrasound, early embryo loss, a previous endometritis, and age 10 or older. In the published series, 47 to 87% of such mares carried a dormant infection the swab had missed, and the whole activation protocol fits inside one oestrus cycle, so the earlier in the season, the better.
bActivate, a diagnostic aid for the problem mare
bActivate can help establish a correct diagnosis in the chronically infected mare. bActivate initiates growth of resident dormant streptococci, which can then be diagnosed and treated by standard techniques.
Veterinarians call this condition subclinical endometritis, latent uterine infection or dormant endometritis. To the breeder it is the barren mare or the empty mare: covered on time, with good semen, and still not in foal.
Chronic infections prevent establishment of a pregnancy, and might also increase the risk of early fetal loss and abortion in the mare. In our field series, 47% (Hagyard, 30 of 64) to 84% (Kildangan, 16 of 19) of mares still not pregnant at the end of the season, despite fertile stallions and veterinary supervision, were activation-positive for a dormant infection.
Some farms use bActivate as a screening tool to improve diagnosis of endometritis and treatment on all open mares during the off-season, hereby optimizing chances to establish a pregnancy and reduce time to pregnancy.
Repeated uterine infections indicate compromised uterine defense mechanisms predisposing for establishment of infections, acute as well as chronic. As chronic infections can be hard to identify bActivate should be considered for this group of problem mares.
Endometrial fibrosis is induced by ongoing endometrial inflammation. Presence of beta-hemolytic streptococci within the endometrium is expected to induce endometrial inflammation, hereby increasing uterine fibrosis, and consequently decreasing fertility. If endometrial fibrosis can be minimized the number of foals each mare can produce in a lifetime is expected to increase.
Biofilm and dormant reservoirs: Streptococcus zooepidemicus can shelter in a biofilm on the surface of the endometrium and slip into a dormant state deeper in the tissue. Breaking up the biofilm treats the surface but leaves the dormant reservoir untouched, which is why a mare can improve after biofilm treatment and then fail again the following season. Read more about why breaking up the biofilm is not enough.
Is My Mare a Candidate for bActivate?
bActivate is indicated for mares with reduced uterine defence mechanisms and suspected chronic subclinical infection. Use the checklist below as a starting point when discussing with your veterinarian.
Strong indications
- ✓Mare has failed to conceive for two or more consecutive seasons despite breeding to a proven fertile stallion
- ✓Culture-negative swabs combined with unexplained infertility or recurrent uterine fluid on ultrasound
- ✓Previous antibiotic treatment resolved fluid temporarily but fertility did not improve
- ✓History of early embryo loss (before day 15) in multiple seasons
Consider bActivate when
- ✓Mare is 10 years or older with a history of uterine infections or fluid accumulation
- ✓Mare has had repeated bacterial isolations (Strep zoo, E. coli) over multiple seasons
- ✓Mare is an open mare at end of season entering the off-season with no pregnancy
- ✓Mare has documented endometrial fibrosis (category IIB or III) and compromised uterine clearance
bActivate is a prescription veterinary product. Your veterinarian will assess suitability based on reproductive history, clinical examination and ultrasound findings.
Which Mares Benefit Most?
Dormant streptococcal infections can affect mares across all breeds and ages, but certain groups are disproportionately represented in clinical case populations.
Older Broodmares
Uterine defence mechanisms decline with age and parity. Mares aged 10+ with multiple previous foalings have reduced mucociliary clearance and lymphatic drainage, making them more susceptible to persistent infection. Clinical studies include a significant proportion of older mares with long histories of infertility.
Thoroughbred & Sport Horses
High-value thoroughbred and warmblood mares where the economic cost of a missed season is significant. The Kildangan/Godolphin study demonstrated an 89% pregnancy rate in barren thoroughbred problem mares after a single bActivate activation cycle followed by targeted antibiotics from the stud vet.
Repeat Breeders
Mares that cycle normally, accept covering, and produce embryos that consistently fail to implant. The inflammatory environment created by dormant Strep zoo prevents uterine preparation for implantation even when the embryo itself is viable.
When in the Breeding Season to Use bActivate
The bActivate protocol is designed to fit within a normal breeding cycle. Activation and the follow-up veterinary treatment take place approximately one cycle before the intended breeding cycle.
Total time from bActivate administration to breeding-ready: 3-4 weeks. This fits within a standard 21-day oestrous cycle, meaning a single activation cycle before the target breeding cycle.
Off-Season Screening
Some breeding operations use bActivate as a proactive screening tool for all open mares at the end of the season or during the winter off-season. This approach offers several advantages:
- ✓Identifies chronic infections before the next breeding season begins
- ✓Allows a full treatment and recovery cycle without time pressure
- ✓Reduces time to pregnancy at the start of the next season
- ✓Minimises wasted covering cycles on untreated infections
- ✓Particularly valuable for high-value mares where early-season pregnancy is economically important
- ✓Helps farms plan breeding schedules with greater confidence
In clinical series, 47 to 87% of problem mares carried a dormant uterine infection that the standard swab had missed. Off-season screening with bActivate addresses this directly.
The concept behind bActivate (promoting bacterial-activation) was discovered by Morten Rønn Petersen, DVM, PhD and Professor Anders Miki Bojesen, DVM, PhD. They both have extensive experience with bacterial endometritis in mares and have published several scientific papers on the subject.
FAQ
Frequently Asked Questions
Common questions about problem mares, biofilm infections and bActivate activation.
When should bActivate be used on a problem mare?
bActivate is indicated for mares that have failed to conceive for two or more consecutive breeding cycles despite normal ovarian cycles, breeding to a fertile stallion, and negative routine uterine culture. It is also indicated when a mare shows signs consistent with uterine infection (uterine fluid on ultrasound, early embryo loss, irregular cycles) but standard swabs return negative results. Some practices use it as a screening tool for all open mares at the start of the off-season.
What are the signs that a mare has a hidden uterine infection?
The main signs are: failure to conceive despite multiple breedings to a fertile stallion, a negative routine uterine swab that does not explain the fertility failure, accumulation of uterine fluid visible on ultrasound around oestrus, early embryo loss (days 14 to 25 after ovulation), and a history of two or more open seasons. These signs combined with a negative swab are the classic presentation of dormant subclinical endometritis caused by Streptococcus zooepidemicus in non-pregnant mares.
How many failed breeding attempts before trying bActivate on a non-pregnant mare?
Most veterinarians consider bActivate after two failed consecutive breeding cycles in a mare with no other identifiable cause. The Hagyard clinical study included mares barren for 3 or more consecutive seasons. In high-value mares or mares approaching the end of their breeding career, earlier investigation may be warranted. Some practices use bActivate as a routine diagnostic on all non-pregnant mares at the end of each breeding season.
Can bActivate be used on any non-pregnant mare or barren mare?
bActivate is intended for non-pregnant mares (also called barren mares or problem mares) suspected of having dormant subclinical uterine infections caused by Streptococcus equi subspecies zooepidemicus. It is administered by a veterinarian and is most appropriate for mares with unexplained fertility failure and negative routine cultures. It is not a first-line tool for mares with acute visible signs of infection such as purulent discharge or positive routine culture results.
Should bActivate be used before or after antibiotics?
bActivate should be used before antibiotics when the goal is accurate diagnosis. Administering antibiotics before bActivate may suppress bacterial reactivation and produce a false-negative post-activation culture. The correct protocol is: instil bActivate, obtain a post-activation culture 48 hours later, then begin targeted antibiotic therapy based on the culture result. The mare is not bred in the same oestrus cycle but in the following one.
Is bActivate used instead of a standard uterine swab?
No. bActivate is used in addition to standard diagnostic procedures, not instead of them. The recommended protocol includes a pre-activation culture before bActivate instillation and a post-activation culture 48 hours later. Comparing the two cultures confirms whether dormant bacteria were present. bActivate does not replace routine culture but extends diagnostic accuracy to mares with dormant infections that standard culture would otherwise miss.
Can bActivate be used during the breeding season?
Yes. bActivate is designed for use during the active breeding season. It is administered during early oestrus when the largest follicle is 25 to 30 mm. The mare is not bred in that same oestrus cycle. After a positive post-activation culture and appropriate antibiotic treatment, the mare is bred in the following cycle. In clinical studies this approach achieved an 83% pregnancy rate in problem mares that had previously failed to conceive.
Continue reading