Study challenges assumptions about “knee chips” in Thoroughbred yearlings

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The discovery of carpal osteochondral fragments (COF), commonly known as “knee chips,” on
pre-sale radiographs has long been viewed as a red flag in the Thoroughbred industry. Horses showing these lesions are often discounted at auction because buyers assume they will be less likely to succeed on the racetrack. However, new research suggests that this long-held belief may not be as straightforward as previously thought.

A study published in the Equine Veterinary Journal by researchers at the University of Kentucky's Maxwell H. Gluck Equine Research Center is the first to directly compare sales and racing outcomes of Thoroughbred yearlings with COF against a matched population of radiographically clean horses. The findings indicate that while the presence of COF can negatively affect both sales and racing performance, arthroscopic surgery may help mitigate some of those disadvantages.

“The idea came from seeing a large number of these cases get significantly marked down in price, just because people assume a chip means the horse won’t perform,” said Bruno Menarim, one of the study’s senior authors. “That was possibly true in the ’80s and part of the ’90s, but not with current arthroscopic surgery approaches.”

Researchers reviewed clinical records from Hagyard Equine Medical Institute between 2015 and 2018 and identified 46 Thoroughbred yearlings with dorsal osteochondral fragments of the radial or intermediate carpal bones. Twenty-six horses underwent arthroscopic removal of the fragments before sale, while 20 were managed conservatively. A control group of 138 sire- and year-matched siblings without radiographic abnormalities was also assembled.

The team then tracked sales and racing records up to June 2023, examining variables including sale price, career earnings, average earnings per start, number of starts, seasons raced, highest speed figure achieved and the highest class of race reached.

Overall, the presence of COF was associated with lower sale prices and reduced lifetime earnings, regardless of treatment. Horses in both the surgical and non-surgical groups also recorded fewer starts and raced for fewer seasons than their unaffected counterparts.

However, important differences emerged when treatment was considered. Horses whose fragments were removed arthroscopically were significantly more likely to achieve a racing career than those managed conservatively. Statistical analysis showed surgically treated horses had more than six times the odds of making it to the racetrack compared with untreated horses.

Perhaps more importantly from a commercial perspective, surgically treated horses were not significantly different from the control group in either sale price or total earnings. In contrast, untreated horses were heavily penalised at auction and earned significantly less during their racing careers.

“In other words, the gap between a surgically treated horse and a clean horse was not statistically significant,” Menarim explained. “The gap between an untreated horse and a clean horse was.”

The researchers also noted that the average difference in sale price between treated and untreated horses was nearly $2,000 - roughly equivalent to the cost of the surgery itself.

The study’s authors caution that the relatively small sample size and single-centre design limit the broader applicability of the findings. Nevertheless, the results suggest that while a history of COF can affect buyer perception, arthroscopic removal may preserve both sales appeal and future athletic potential.

For consignors and owners faced with a yearling diagnosed with a knee chip, the research offers reassurance that the lesion itself need not be career-defining - particularly when modern surgical treatment is employed.

For more details, see:

 

Daria C Debald, Victoria L Stanton, Cole B Sandow, Dwayne H Rodgerson, Michael A Spirito, Robert J Hunt, Bruno C Menarim.

Racing and sales performance in Thoroughbred yearlings after carpal osteochondral fragment removal.

Equine Vet J. 2026;58(3):682–691

https://doi.org/10.1111/evj.14532

Gothenburg Zoo horses remain calm around visitors, study finds

Dennis Björklund CC BY-SA 3.0

  

Visitors to zoos and animal parks often wonder how their presence affects the animals they
come to see. A new study from the University of Gothenburg offers reassuring news for animal keepers and visitors alike: the horses at Gothenburg's Children's Zoo appear comfortable around people, even when surrounded by groups of enthusiastic children.

Animal welfare encompasses both the physical and psychological wellbeing of animals and is a key concern for zoos and other organisations that keep animals in captivity. Understanding how animals respond to visitors is particularly important in facilities involved in conservation and breeding programmes, as stress can negatively affect health and reproduction.

To investigate whether human activity influences the welfare of horses at Slottsskogen, a large city park in Gothenburg, Sweden, researchers from the Department of Biological and Environmental Sciences, University of Gothenburg, monitored the heart rates of eight Gotland russ horses. Heart rate is widely used as an indicator of stress because it rises when animals experience physical exertion or emotional strain.

Lead researcher Isidora Dundjerovic and her colleagues fitted the horses with Polar heart rate monitors and measured their heart rates under three different conditions: while resting, during exercise, and during a playground event in which the horses stood in a paddock next to a children's play area and were petted by visitors while eating hay.

The results showed clear differences between the three situations. The horses' average resting heart rate was 42.5 beats per minute (bpm), while exercise increased it to an average of 85 bpm. During the playground event, however, the average heart rate was only 51 bpm - higher than at rest but far below the level recorded during exercise.

These findings suggest that interaction with visitors was not a significant source of stress for the horses. In fact, despite being surrounded by children and adults, the animals remained relatively calm throughout the event.

The study also provided insight into how the horses reacted to other common features of the urban park environment. During their daily walks, the horses encountered barking dogs, passing cars and other animals. None of these appeared to trigger a measurable stress response.

One exception stood out. During one playground session, an excavator unexpectedly started operating close to the paddock. The horses' heart rates rose sharply, and they quickly moved away from the machine. This reaction indicated that loud mechanical noise was stressful, unlike the presence of visitors or routine park activity.

"Horses have lived alongside humans for thousands of years," says Dundjerovic. "We now know a little more about how they are affected by being in an environment with lots of people, which is important for ensuring their welfare."

The findings are encouraging for the staff responsible for caring for the animals at the Children's Zoo. According to zoologist Linda Thelin, animal welfare is monitored closely through a variety of methods, and physiological studies such as this help identify sources of stress that may not be obvious from behaviour alone.

As zoos continue to balance conservation, education and public engagement, studies like this provide valuable evidence to guide management decisions. For the horses at Gothenburg's Children's Zoo, it appears that friendly human attention is not a problem - but noisy construction equipment is another matter entirely.

 

For more details, see:

Dundjerovic, I., and L. U. Sneddon. 2026.

Heart Rate as an Indicator of Stress in Gotland's Russ Horses.

 Zoo Biology 45: 293-299.

https://doi.org/10.1002/zoo.70052

New genetic discovery explains fatal neurological disease in Quarter Horse foals

   

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Researchers at the UC Davis School of Veterinary Medicine have identified the genetic cause of Equine Juvenile Spinocerebellar Ataxia (EJSCA), a recently recognised and fatal neurological disease affecting American Quarter Horse foals. The discovery not only provides breeders with a genetic test to prevent affected foals from being born, but also advances scientific understanding of neurological disease in both horses and humans.

EJSCA is an inherited neurological disorder that affects foals within the first few weeks of life. Clinical signs typically develop between one and five weeks of age and progress rapidly. Affected foals initially appear uncoordinated and exhibit proprioceptive ataxia, meaning they have difficulty determining the position of their limbs in space. Within days, many develop severe weakness of the hind limbs, become unable to stand without assistance, and eventually require euthanasia on welfare grounds.

The disease results from degeneration of axons, the long nerve fibres that connect neurons and allow communication between the brain, spinal cord and limbs. As these pathways deteriorate, the nervous system can no longer accurately transmit information about movement and body position. Consequently, affected foals lose balance and coordination despite appearing normal at birth.

The first recognised case of EJSCA was identified in 2020 in a Quarter Horse filly known as “Curly Sue.” Veterinarians initially suspected another neurological condition, equine neuroaxonal dystrophy (eNAD), but further investigations revealed that the foal was suffering from a previously unrecognised disease.

To identify the genetic cause, researchers at UCDavis performed whole-genome sequencing on seven affected foals and compared their DNA with that of unaffected relatives and unrelated control horses. The investigation identified an 82-kilobase region on chromosome 11 that contained several candidate genetic variants. Further molecular studies demonstrated that the causative mutation was located within a non-coding region of the ferredoxin reductase (FDXR) gene.

Unlike many disease-causing mutations that alter the protein-coding sequence of a gene, this mutation affects how the gene is processed into messenger RNA. The variant causes the insertion of a cryptic exon - a segment of genetic material that is not normally included in the final RNA transcript. As a result, affected foals produce lower amounts of functional FDXR protein.

This finding is significant because FDXR plays an important role in cellular energy metabolism and nervous system function. Analysis of spinal cord and liver tissues showed that affected foals had substantially reduced FDXR protein concentrations compared with healthy controls. Importantly, mutations in the human FDXR gene are known to cause neurological disease, making EJSCA a potentially valuable natural model for studying similar disorders in people.

The researchers determined that EJSCA follows an autosomal recessive pattern of inheritance. This means that affected foals inherit two copies of the mutation, one from each parent. Horses carrying only one copy remain clinically normal but can pass the variant to their offspring. When two carrier horses are bred together, there is a 25% chance of producing an affected foal.

Screening of more than 1,000 Quarter Horses identified 25 carriers, indicating that the mutation currently occurs at a relatively low frequency within the breed. It has not yet been detected in other horse breeds. Because all known affected foals trace back to a single influential sire, researchers believe the mutation may have arisen relatively recently.

The development of a genetic test by the UC Davis Veterinary Genetics Laboratory now allows breeders to identify carrier animals before breeding. By avoiding carrier-to-carrier matings, breeders can effectively prevent the birth of affected foals while maintaining valuable bloodlines. This discovery represents the first non-coding neurological genetic variant identified in horses and the first known genetic cause of a degenerative axonal disease in the species, marking an important milestone in equine genetics and neurological research.

 

For more details, see:

Brown, B. N., Dahlgren, A. R., Ghosh, S., Durbin-Johnson, B., Willis, A., Olivas, C., York, D., Grahn, R., Bellone, R. R., Cortopassi, G. A., Miller, A. D., Brown, C. T., Woolard, K., & Finno, C. J. (2026).

An intronic variant in Ferredoxin Reductase (FDXR) creates a cryptic exon in Quarter Horses with Equine Juvenile Spinocerebellar Ataxia. 

PLoS genetics, (2026). 22(5), e1012158.

https://doi.org/10.1371/journal.pgen.1012158

Pseudomonas aeruginosa in horses and other animals

  

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Pseudomonas aeruginosa is an environmentally widespread bacterium found naturally in soil and water. Although it
is often harmless in the environment, it is an important cause of disease in both human and veterinary medicine. The bacterium is particularly concerning because it possesses a high level of intrinsic resistance to many antibiotics, has a remarkable ability to adapt genetically, and can form resilient biofilms that protect it from both the host immune system and antimicrobial treatments.

 

The World Health Organisation (WHO) has designated P. aeruginosa as a "Priority Pathogen" due to its role in antimicrobial resistance. It is also one of the six bacterial species that make up the ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species). These bacteria are responsible for many hospital-acquired infections worldwide and are notorious for their ability to evade antibiotic treatment.

 

In horses, P. aeruginosa is associated with several important diseases, including genital tract infections, respiratory disease and ocular infections. In mares, infection can contribute to infertility and pregnancy-related problems, making it a significant pathogen in equine breeding operations.

 

To better understand the occurrence of P. aeruginosa in animal populations, Kellie Strickland and colleagues at the University of the Sunshine Coast, Australia, conducted a large-scale epidemiological study. The researchers analysed 1,669 DNA samples collected between 2010 and 2023 from a variety of healthy and diseased animals in South-East Queensland. The study included samples from wild birds, domestic animals, livestock, kangaroos and koalas.

 

Overall, the prevalence of P. aeruginosa was relatively low, with only 1.8% of all samples testing positive. However, livestock had the highest prevalence (4.5%), largely driven by horses, which showed a prevalence of 7.4%. This was considerably higher than the rates observed in wild birds (1.5%), koalas (1.6%) and other domestic animals (1.9%). No positive samples were detected in cattle or kangaroos.

 

Of particular concern was the detection of a genetic mutation known as GyrA Thr83Ile in two horse-derived P. aeruginosa samples. This mutation has previously been associated with resistance to fluoroquinolones, a class of antibiotics commonly used to treat P. aeruginosa infections in both humans and horses. Although the researchers were unable to confirm antibiotic resistance through laboratory culture and susceptibility testing, the presence of this mutation suggests that a resistant subpopulation may be emerging within the equine population.

 

The findings highlight the importance of ongoing surveillance of antimicrobial resistance in horses. While the overall prevalence of P. aeruginosa was low, the relatively high carriage rate in horses and the detection of a clinically important resistance-associated mutation warrant further investigation.

 

For more details, see:

Prevalence of Pseudomonas aeruginosa in Australian wild birds, native wildlife, livestock and domestic animals

Kellie R. Strickland, Martina Jelocnik, Erin P. Price & Derek S. Sarovich 

Scientific Reports (2026) vol 16, Article number: 15423 (2026) 

https://www.nature.com/articles/s41598-026-43853-6

Exercise, the gut microbiome and health

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 The gut microbiome - the diverse community of bacteria, fungi, viruses and other microorganisms that inhabit the gastrointestinal tract - has become a major focus of research in both human and veterinary medicine.

 

Far from being passive inhabitants, these microorganisms play a crucial role in host health, influencing digestion, metabolism, immune function and even neurological processes. Growing evidence suggests that the composition and diversity of the gut microbiome can affect susceptibility to a wide range of conditions, including obesity, cardiovascular disease, autoimmune disorders and inflammatory diseases.

 

In human medicine, among the many factors that influence the microbiome, regular physical activity has emerged as one of the most important. Exercise is widely recognised for its benefits to digestive and systemic health, and research indicates that many of these effects may be mediated through changes in the gut microbiota. Regular moderate-to-vigorous exercise has been shown to increase microbial diversity, a characteristic strongly associated with better physical and mental health.

 

In contrast, reduced microbial diversity has been observed in individuals with obesity, cardiometabolic disease and certain autoimmune conditions.

 

While these effects are increasingly well documented in humans, less is known about the relationship between exercise and the gut microbiome in horses. A recent study, published in  Microbial pathogenesis, investigated this question by examining the effects of exercise on equine gut bacterial and fungal communities using 16S rDNA and ITS gene amplicon sequencing.

 

The results demonstrated that exercise significantly increased bacterial diversity, as reflected by higher ACE, Chao1 and Shannon diversity indices - commonly used measures of microbial diversity in ecological and microbiome studies. The increases in ACE and Chao1 suggest that exercise was associated with a greater number of bacterial taxa in the gut, while an increase in the Shannon index indicated that the bacterial community became both richer and more evenly distributed. Together, these findings suggest that exercise promoted a more diverse gut bacterial ecosystem.

 

Exercise also altered the overall composition of the bacterial community. Specifically, the relative abundance of eight bacterial phyla and 187 bacterial genera increased, while three phyla and 197 genera decreased significantly.

 

In contrast, exercise had little effect on the overall diversity and abundance of the fungal community, although significant changes were observed in the abundance of specific fungal taxa. Exercise increased the relative abundance of five fungal phyla and 105 genera, while reducing two phyla and 82 genera.

 

These findings indicate that exercise can substantially modify the composition and structure of the equine gut microbiota, particularly the bacterial component. The study supports the growing concept that exercise may promote health by shaping the gut microbial ecosystem.

 

Future research examining different exercise types and intensities may further clarify how physical activity can be used to optimise microbiome health and improve management strategies in both humans and horses.

 

For more details, see:

 

Ma, Rufei., & Wang, Chong.

Microbiome analysis reveals the positive effects of exercise on the gut microbiota in horse. 

Microbial pathogenesis (2026) , 216, 108501.

https://doi.org/10.1016/j.micpath.2026.108501

 

Could ertugliflozin reduce laminitis risk following corticosteroid joint injections?

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Intra-articular (IA) corticosteroid injections are widely used in equine practice to manage joint
pain and inflammation associated with conditions such as osteoarthritis. One commonly used corticosteroid is triamcinolone acetonide (TA), which can provide significant relief from lameness and improve performance. However, growing evidence suggests that even when corticosteroids are administered directly into a joint, they can have effects throughout the body, including alterations in blood glucose and insulin concentrations.

This is important because elevated insulin concentrations (hyperinsulinaemia) are strongly associated with endocrinopathic laminitis, one of the most common and serious causes of laminitis in horses. Horses with Equine Metabolic Syndrome (EMS) or insulin dysregulation (ID) are considered particularly vulnerable, but any horse experiencing a substantial increase in insulin may be at risk.

Researchers have recently investigated whether ertugliflozin, a member of the sodium-glucose co-transporter 2 inhibitor (SGLT2i) drug class, could help reduce these post-corticosteroid insulin increases. In human medicine, SGLT2 inhibitors are commonly used to treat Type 2 diabetes by promoting the excretion of glucose through the urine, thereby reducing blood glucose and insulin levels. More recently, these drugs have attracted attention in equine medicine as a treatment for severe insulin dysregulation.

Two independent studies have now examined the effects of ertugliflozin administration around the time of IA corticosteroid treatment in horses.

The first study, conducted by Page and colleagues at the University of Kentucky, used eight metabolically normal geldings in a controlled crossover design. Horses either received no treatment or were given ertugliflozin for seven days before and seven days after receiving a clinically relevant dose of triamcinolone acetonide. Researchers measured resting glucose and insulin concentrations and performed oral sugar tests to assess the horses' insulin responses.

The results showed that horses receiving ertugliflozin had significantly lower blood glucose and insulin concentrations following corticosteroid administration. Resting glucose concentrations remained lower for up to 48 hours after injection, while resting insulin concentrations were lower for up to 72 hours. Insulin responses during oral sugar testing were also reduced. Importantly, no obvious adverse effects were observed during the study.

A second study by Darch and colleagues produced similar findings. Using a randomised, blinded, placebo-controlled crossover design, eight Standardbred geldings received either ertugliflozin or a placebo before and after IA triamcinolone administration. The researchers monitored blood insulin, glucose and triglyceride concentrations over the treatment period.

Again, ertugliflozin substantially reduced the insulin response following corticosteroid injection. The peak insulin concentration (Cmax) was approximately 40 μIU/mL in the placebo group but only 17 μIU/mL in horses receiving ertugliflozin. Statistical analysis indicated a greater than 99% probability that the peak insulin concentration was lower when horses received ertugliflozin.

Together, these studies provide encouraging evidence that ertugliflozin can attenuate the increases in blood glucose and insulin that occur following IA corticosteroid administration. This finding is particularly relevant because corticosteroid-associated hyperinsulinaemia may contribute to laminitis risk.

However, both studies were conducted in horses that did not have insulin dysregulation. Consequently, the most important question remains unanswered: can ertugliflozin reduce post-corticosteroid insulin elevations in horses already suffering from EMS or ID, where the risk of laminitis is greatest?

Further research is now needed to determine whether this treatment strategy can safely protect high-risk horses. If successful, ertugliflozin could become an important tool that allows veterinarians to continue using corticosteroid joint injections while reducing the metabolic complications that may accompany them.

 

For more details,see:

1) Allen E Page,  Jenna L McPeek,  Ella McGreevy,  Sophia Carattini,  Emma N Adam.  

Treatment with ertugliflozin mitigates the hyperinsulinemic response to intra-articular triamcinolone acetonide. 

Equine Vet J.  2026.

https://doi.org/10.1002/evj.70150

 

2) Cara Darch, Timothy H. Hyndman, David Byrne, David Ian Rendle, Barny Fraser,

Ertugliflozin decreases the insulin spike in non-insulin dysregulated standardbred horses following intra-articular triamcinolone administration,

Domestic Animal Endocrinology, (2026) Vol 96,107016,

https://doi.org/10.1016/j.domaniend.2026.107016

Free webinar supports call for posters for Horses Inside Out Conference 2027

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A call has been made for scientific posters centred on the theme of wellness and welfare for the
2027 Horses Inside Out Conference. Equine coaches, therapists, and industry professionals are being encouraged to contribute research, case studies, and practical observations as part of the conference programme.

The initiative provides an opportunity for professionals within the equine sector to present their expertise in a scientific format and contribute to ongoing discussions surrounding equine wellness and welfare. Contributors are invited to transform their practical experience and case studies into engaging scientific posters that may help advance understanding within the field.

To support participants through the process, Professor Meriel Moore-Colyer will host a free webinar entitled “Mastering Scientific Posters” on Monday 1st June. The webinar is designed to guide attendees through each stage of poster creation, including selecting an appropriate topic, developing ideas, and designing an effective and visually compelling scientific poster.

The webinar aims to make the process accessible and supportive for those who may feel unfamiliar with scientific poster presentation, while encouraging wider participation in equine science and welfare discussions.

For more details, see: 

https://www.horsesinsideout.com/webinars

 

Effects of a fibre-based forage feed on hindgut fermentation and microbiome

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As understanding of equine gut health continues to evolve, increasing attention is being focused on the relationship between diet and the horse’s hindgut microbiome. The microbial community structure (MCS) within the hindgut plays a critical role in fibre digestion, nutrient utilisation, immune support, and overall gastrointestinal health. Although numerous commercial feeds and supplements are marketed to support digestive function and optimise nutrition, relatively little research has examined how these products influence the equine hindgut microbiome.

 

Newly published research conducted by K.J. Hart, M.J. Hegarty, E.H. Hart at Aberystwyth University sought to address this knowledge gap by investigating the effects of a complementary fibre-based forage feed* on hindgut fermentation and microbial community structure under controlled laboratory conditions.

 

The study aimed to evaluate how the feed influenced fermentation profiles and microbial populations when added to two contrasting basal diets: a forage-only diet (FOR) and a mixed forage-and-concentrate diet (MIX). Researchers used an in vitro hindgut fermentation model designed to simulate conditions within the equine large intestine.

 

While in vitro systems cannot replicate every aspect of the living horse, they provide valuable tools for studying microbial activity under carefully controlled conditions. These laboratory models allow researchers to isolate dietary effects without the many variables present in live-animal trials. However, the authors acknowledged that such systems cannot fully reproduce the complexity of the equine gastrointestinal tract, including immune responses, intestinal motility, hydration dynamics, stress, exercise, and long-term microbial adaptation.

 

Using a 2 × 2 factorial design, the researchers examined fermentation characteristics and microbial community changes in vessels receiving either the forage-only or mixed diet, with or without inclusion of the fibre-based feed. Each treatment was replicated three times. Artificial saliva was continuously infused into the fermenters, and feed bags were incubated for 24 and 48 hours to assess microbial community structure.

 

The study demonstrated clear differences between the two basal diets. The MIX diet produced a lower hindgut pH and higher total volatile fatty acid production compared to the forage-only diet, indicating altered fermentation activity. These findings reinforce existing knowledge that concentrate inclusion can significantly influence hindgut fermentation patterns.

 

Researchers also identified significant differences in microbial community composition between the two diet types at both 24 and 48 hours. In particular, an interaction involving Proteobacteria was observed at 24 hours, with levels highest in the MIX diet supplemented with the fibre-based feed. However, beyond this isolated interaction, the inclusion of the forage feed caused no substantial additional changes to the overall microbial community structure.

 

Importantly, the researchers concluded that the fibre-based feed produced “no negative effects” on fermentation parameters or microbial composition within the in vitro model. In practical terms, this suggests the feed was compatible with normal hindgut fermentation processes and did not disrupt microbial balance under the conditions tested.

 

The findings are significant because they contribute to a growing body of research examining how equine diets influence gut microbial ecology. However, the authors’ conclusions remained appropriately cautious. The study did not evaluate live horses, clinical health outcomes, performance measures, or long-term feeding effects. Instead, it provided an initial laboratory-based assessment of how a fibre-based feed interacts with hindgut fermentation systems.

 

Overall, the research suggests that inclusion of the tested fibre-based forage feed did not adversely affect hindgut microbial activity in vitro, while also highlighting the substantial influence that basal diet composition exerts on equine fermentation dynamics and microbial community structure.

 

*EquidGel®

 

For more details, see:

K.J. Hart, M.J. Hegarty, E.H. Hart,

An investigation into the impact of the inclusion of a commercial fiber-based feed, designed for both hydration and nutrition, on the equine hindgut microbiomes,

Journal of Equine Veterinary Science (2026) Vol 161, 105862,

https://doi.org/10.1016/j.jevs.2026.105862

Black soldier fly larvae for treating horse manure

Black soldier fly larvae composting manure 

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Managing horse manure remains a significant challenge for the equine industry. Large volumes
of waste are produced daily by stabled horses, and disposal can be costly, labour-intensive, and environmentally problematic. In addition to the sheer quantity of manure generated, its nutrient composition can vary widely, and it may also contain residues of veterinary medications such as moxidectin, a commonly used antiparasitic drug. These factors complicate composting and land application practices, prompting researchers to explore more sustainable and efficient waste-management solutions.

A novel study led by Yanting Guo at the University of Findlay, Ohio,  investigated whether black soldier fly larvae (BSFL) could provide an innovative biological approach to processing horse manure. The research examined the ability of BSFL to reduce manure mass while transforming nutrients into potentially useful by-products such as natural fertiliser.

Black soldier flies are increasingly attracting scientific and agricultural interest because of their remarkable waste-processing abilities. Unlike common houseflies and blowflies, black soldier flies are not considered pests to humans. Adult flies possess greatly reduced mouthparts and consume little or no food, meaning they do not regurgitate material or spread pathogens in the way houseflies commonly do. Their larvae are also substantially larger and more competitive than other fly species, often suppressing the development of nuisance flies by consuming resources before other larvae can establish themselves. As a result, BSFL-based composting systems tend to produce less odour and are generally considered more hygienic and environmentally friendly.

The study evaluated how effectively BSFL could process horse manure collected from four horses treated with moxidectin. Researchers compared larvae raised on manure with a control group fed standard chicken feed. Over the course of the experiment, the team assessed larval survival, growth rates, dry mass reduction, and nutrient transformations within the manure.

The results were highly encouraging. Black soldier fly larvae demonstrated exceptionally high survival rates of between 98 and 100 percent across all feeding substrates, indicating that horse manure, even when containing pharmaceutical residues, could successfully support larval development.

Interestingly, larvae reared on horse manure initially outperformed those fed chicken feed. During the first half of the experimental period, the manure-fed larvae achieved greater body weight and longer body length than the control group, suggesting that horse manure may provide a surprisingly effective nutritional resource for BSFL growth. Growth later plateaued during the second half of the trial, but the larvae remained healthy and viable throughout.

One of the most important findings involved waste reduction. Within just 15 days, BSFL treatment significantly reduced the dry mass and carbon content of the manure. This demonstrates the larvae’s impressive ability to rapidly break down organic waste material, potentially reducing the volume of manure requiring storage or disposal on equine properties. 

The study also revealed important changes in nutrient composition following larval treatment. Levels of total phosphorus, potassium, calcium, magnesium, zinc, manganese, and copper decreased after processing. However, several valuable nutrients — including total nitrogen, available phosphorus, sodium, sulphur, boron, and iron — were largely retained. The carbon-to-nitrogen ratio also remained relatively stable, suggesting the remaining material may still possess strong fertiliser value for agricultural use.

Overall, the findings demonstrate that black soldier fly larvae could offer a practical and environmentally sustainable strategy for managing horse manure. By simultaneously reducing waste volume and converting manure into nutrient-rich fertiliser material, BSFL systems may provide horse owners and equine facilities with an innovative approach to improving manure management while supporting circular agricultural practices.

 

For more details, see:

Yanting Guo, Victoria Ritzler, Susan Grube,

Bioconversion of horse manure using black soldier fly (Hermetia illucens) larvae: growth, waste reduction and nutrient dynamics,

Next Research (2026) Vol 9,101726.

https://doi.org/10.1016/j.nexres.2026.101726

Transient hindlimb asymmetry following intramuscular vaccination in horses

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Vaccination is an essential part of preventative healthcare in horses and plays a major role in
protecting equine populations from infectious diseases such as influenza and tetanus. Most vaccines are administered by intramuscular injection, meaning the vaccine is delivered directly into a muscle. Although vaccination is considered safe and routine, mild side effects can occasionally occur.

 

A recent study investigated whether intramuscular vaccination into either the semitendinosus muscle or the pectoralis descendens muscle could temporarily affect a horse’s movement and gait.

 

The semitendinosus is one of the large muscles located in the horse’s hindquarters. It forms part of the hamstring muscle group and contributes to propulsion during movement, particularly when the horse pushes off the ground during walking, trotting, or cantering. Because of its size and accessibility, this muscle is sometimes used as an injection site for vaccines or medications.   The pectoralis descendens (also known as the cranial superficial pectoral muscle) forms part of the ‘thoracic sling’ between the front legs that supports the torso. It is a common site for intra-muscular Injections.

 

The study found that routine intramuscular vaccination into the semitendinosus  resulted  in a “transient, measurable push-off-type hindlimb asymmetry.” In simpler terms, the vaccinated horses showed a temporary unevenness in the way they used their hindlimbs during movement. This asymmetry was most noticeable 48 hours after vaccination but had resolved by 96 hours.

 

A “push-off-type” asymmetry refers to changes occurring during the propulsion phase of movement. During locomotion, the hindlimbs generate the force needed to push the horse forward. If one hindlimb produces less force because of soreness or stiffness, the horse may shift more weight onto the opposite limb. This can create a subtle unevenness in gait that may resemble mild lameness.

 

The asymmetry observed in the study was described as measurable, meaning it could be detected using objective gait analysis techniques. Modern gait analysis often uses motion sensors or inertial measurement units attached to different parts of the horse’s body. These devices can identify very small changes in movement that may not always be visible to the human eye. Such technology is increasingly used in equine sports medicine to improve the accuracy of lameness detection.

 

The research team did not detect any clinically relevant changes in gait symmetry following vaccination into the pectoralis descendens or after saline (control) injection at either site.

 

Importantly, the effect observed after vaccination in the semitendinosus muscle was temporary and short-lived. The horses returned to normal symmetry within four days of vaccination, suggesting that the effect was likely related to temporary muscle soreness or mild local inflammation at the injection site rather than any serious injury. Mild inflammation is a normal immune response following vaccination, as the body reacts to the vaccine and begins developing immunity.

 

This finding is particularly relevant for veterinarians, owners, trainers, and equine therapists because temporary gait asymmetry following vaccination could potentially be mistaken for orthopaedic lameness or poor performance. Horses competing or undergoing lameness investigations shortly after vaccination may therefore show altered movement patterns unrelated to musculoskeletal disease.

 

The study also highlights the importance of appropriate vaccination scheduling. Since measurable asymmetry occurred around 48 hours after injection, strenuous exercise or competition immediately after vaccination may not be ideal. Many veterinarians already recommend a short period of lighter work following vaccination to allow horses time to recover from any mild soreness or systemic effects.

 

Overall, the study suggests that intramuscular vaccination into the semitendinosus muscle may cause short-term hindlimb asymmetry, but the effect appears mild, temporary, and self-resolving in healthy horses.

 

For more details, see:

 

J. Lenarz, I.H. Smit, M. Rhodin, C. Lischer, M.C. Fugazzola,

Vaccination-associated lameness in warmblood horses after intramuscular injection,

Journal of Equine Veterinary Science (2026), Vol 159,105820.

 

https://doi.org/10.1016/j.jevs.2026.105820