Equine Digest: muzzles, outbreak protocols, and stall-side tests

Editor's note

This issue leans practical. Most of what came through the peer-reviewed pipeline over the last two weeks lands on the same question: when do you reach for a test, a tool, or a treatment, and what does it actually buy you? A grazing muzzle that halves a summer insulin spike, a plasma-and-antiviral protocol during a herpesvirus scare, a stall-side progesterone reader, a refractometer for newborn foals, and a fresh look at a strangles blood test all speak to decisions you make at the barn, not in a lab. Two of the papers also carry a useful warning: a widely used ulcer drug and a cheap foal screen both have limits worth knowing before you lean on them. We have flagged those limits plainly.

A grazing muzzle roughly halved the summer insulin spike in metabolic horses

Owners of horses with insulin dysregulation (a faulty insulin response that drives laminitis risk, the core problem in equine metabolic syndrome, or EMS) usually hear one instruction: keep them off grass. This crossover study put nine insulin-dysregulated horses out on summer pasture for ten hours, twice each with a muzzle and twice without, and sampled blood every two hours. Peak insulin was about half as high when horses wore the muzzle (24 versus 46 microIU/mL). Pasture sugar content (nonstructural carbohydrate, the fraction that spikes insulin) and individual horses both varied a lot, so the authors stress repeat monitoring rather than treating a muzzle as a fix. Still, for a horse that lives out, this is direct support that a muzzle can blunt the metabolic hit of turnout.

Bottom line

For a horse with EMS or laminitis risk, a grazing muzzle can meaningfully lower the insulin surge from summer grass, though it does not replace watching each horse individually.

Askins MJ, Harris PA, McClendon ME, Adams AA (2026). Journal of Equine Veterinary Science. DOI: 10.1016/j.jevs.2026.106095.

An antiviral-plus-heparin protocol was tied to better survival in a herpesvirus outbreak

Equine herpesvirus type 1 (EHV-1) is the barn nightmare that can progress to the neurologic form, equine herpesvirus myeloencephalopathy (EHM), where horses become wobbly or go down. This multicenter review followed 111 horses naturally exposed during real outbreaks, confirmed by PCR (a test that detects the virus's genetic material). Of the horses treated with valacyclovir (an antiviral) plus heparin (a blood thinner), all survived. The four confirmed cases given neither drug all developed the most severe grade of incoordination and were euthanized. Giving valacyclovir before signs appeared, and heparin once signs started, tracked with fewer neurologic cases. This is a retrospective look at modest numbers, not a controlled trial, so it cannot prove the drugs caused the difference. It does give vets and barn managers a concrete protocol to weigh when an outbreak hits.

Bottom line

In confirmed EHV-1 outbreaks, a valacyclovir-and-heparin protocol was associated with fewer neurologic cases and better survival, worth discussing with your vet before an outbreak reaches your barn.

Marchitello M, Estell K, Ludwig EK, Sage AM, White NA (2026). Journal of the American Veterinary Medical Association. DOI: 10.2460/javma.26.02.0118.

A new blood test spotted strangles more accurately than the old one

Strangles (infection with the bacterium Streptococcus equi) is one of the most contagious diseases a yard can face, and reliable blood testing matters for screening new arrivals and finding silent carriers. Researchers screened 89 bacterial proteins, found a promising one they named P92, and built it into an ELISA (a common antibody blood test). Across more than 200 horses, the P92 test scored 95% on a standard accuracy measure, beating the older SeM-protein test at 88%, and it correctly separated true strangles from a related bacterium that can muddy results. Better accuracy means fewer horses wrongly cleared or wrongly flagged during an outbreak or a pre-arrival quarantine. The test still needs commercial rollout, but the target is now identified and validated in good numbers.

Bottom line

A newly identified protein gives a more accurate strangles blood test, which should sharpen biosecurity screening and carrier detection once it reaches practice.

Cohen ND, et al. (2026). Journal of the American Veterinary Medical Association. DOI: 10.2460/javma.26.02.0149.

Heavy omeprazole use was linked to more lung bleeding in racehorses

Omeprazole (the active ingredient in GastroGard and UlcerGard) is one of the most-reached-for drugs in any tack room. This study tracked nearly 3,000 racehorses and found that higher cumulative omeprazole in the previous 30 days went along with a modestly higher hazard of detected exercise-induced pulmonary hemorrhage (EIPH, bleeding in the lungs during hard work). The size was small, roughly an 8% higher hazard per 10-gram increase in dose, and links to fracture and irregular heartbeat were essentially absent. This is an association in racehorses, not proof that the drug causes bleeding, and it does not mean a horse who needs ulcer treatment should go without. It is a reason to question routine, open-ended, or purely preventive use and to match the drug to a real need.

Bottom line

Heavy cumulative omeprazole was associated with more lung bleeding in racehorses; treat ulcers when they are there, but the finding argues against indefinite or just-in-case dosing.

Jones OJ, Ahern BJ, Stewart BD, Morton JM, Robotham KL, Wise JC (2026). Journal of the American Veterinary Medical Association. DOI: 10.2460/javma.26.04.0319.

A cheap refractometer screens newborn foals, but do not lean on it alone

A foal that does not absorb enough antibody from colostrum has failure of transfer of passive immunity (FTPI), the leading path to newborn sepsis. This study tested a pocket digital Brix refractometer (a cheap stall-side tool) against a lab antibody test in 124 foals at 12 hours old. The two lined up reasonably well, but sensitivity came in below 80%, meaning the refractometer missed a meaningful share of at-risk foals at practical thresholds. That is a limitation the authors call a real handicap for the industry, not a sign the tool is useless. Use it as a quick first screen, and confirm any borderline or worrying foal with a proper IgG (antibody) test rather than trusting a single refractometer reading.

Bottom line

A Brix refractometer is a handy first-pass check for colostrum failure in newborn foals, but its modest sensitivity means borderline foals still need a lab antibody test.

Akköse M, et al. (2026). Acta Veterinaria Hungarica. DOI: 10.1556/004.2026.01271.

Horses read a predator from sight alone, and reactivity depends on the horse

Whether a horse's spook reflects real threat detection or just background noise is hard to test in the field. This study showed 18 horses silent video of a wolf pack and, separately, of harmless grazing wombats, with no sound to give the game away. Heart rate climbed for the wolves but not the wombats, so the horses distinguished a predator on visual cues alone. The reaction was not uniform: older horses were calmer and less clingy, males reacted more strongly than females, and higher-ranking horses showed bigger jumps in heart rate. Horses also tended to view the harmless wombats with both eyes, consistent with curiosity rather than alarm. None of this tells you to change management overnight, but it is a grounded reminder that spookiness is partly wired and varies by age, sex, and herd rank.

Bottom line

Horses can flag a threat from sight alone, and how strongly they react shifts with age, sex, and herd status, so a spooky youngster is not necessarily a badly behaved one.

Hofacker R, Sebunia N, Pihlblad J, Benderlioglu Z (2026). PLoS ONE. DOI: 10.1371/journal.pone.0349298.

A stall-side progesterone test held up against the lab for breeders

Timing a breeding often hinges on progesterone, and waiting on a lab can cost a cycle. This study put a point-of-care (POC, meaning it runs at the barn) progesterone device, the Sidekick, up against two established lab methods. In spiked samples the agreement was near-perfect, and in real mare samples it was substantial against both reference tests. It recovered progesterone accurately across the clinically useful 4 to 8 ng/mL range and did not get thrown off by altrenogest (a common synthetic progestin). The honest limits: it was validated over a narrow range, so it can underread very high values, and a serum-versus-plasma bias showed up. Within its window, though, it gives a fast, reliable number you can act on the same day.

Bottom line

A stall-side progesterone reader gave lab-comparable results in the range that matters for breeding decisions, letting breeders act without waiting on a lab.

McDowell SH, McLain A, Moore L, Ledgerwood CJ, Bailie E, Moore T (2026). Journal of Veterinary Diagnostic Investigation. DOI: 10.1177/10406387261460834.

Coming up

Next issue we will be watching for peer-reviewed follow-up on the objective-lameness-sensor work and a grazing trial suggesting chicory may cut worm burden, both currently sitting in preprint. See you in two weeks.