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Day blooming jasmine poisoning is a progressive form of toxicosis in horses, caused by repeated ingestion of the ornamental shrub Cestrum diurnum. The plant grows in tropical and subtropical regions and may be found in landscaped areas, along fence lines, or in unmanaged pastures.
Day blooming jasmine contains a vitamin D-like compound that disrupts calcium and phosphorus regulation. Over weeks or months of steady intake, excess minerals can accumulate in tendons, ligaments, blood vessels, and internal organs, causing irreversible tissue damage.
Affected horses may develop gradual weight loss, stiffness, and lameness, as well as reluctance to move despite maintaining a normal appetite. Because early signs can resemble chronic orthopedic disease or age-related decline, prompt veterinary evaluation and careful investigation of possible plant exposure are important aspects of diagnosis.
Keep reading to learn how to identify day blooming jasmine, recognize signs of toxicosis, and reduce exposure risks for horses.
Day Blooming Jasmine
Day blooming jasmine (Cestrum diurnum) is an ornamental shrub found throughout many tropical and subtropical regions of the world. It is commonly planted for its attractive white flowers and dense evergreen foliage, but it may escape cultivation and become established along roadsides, fence lines, unmanaged fields, and other disturbed areas.
In the southern United States, particularly Florida, Texas, and other warm coastal regions, horses may encounter the plant in both landscaped and naturalized areas. [1][2]
Day blooming jasmine causes a slowly progressive disease that develops over weeks or months of repeated ingestion. The plant contains a naturally occurring vitamin D-like compound that disrupts the body’s normal regulation of calcium and phosphorus. [1][2]
Because poisoning develops slowly, early clinical signs are often subtle and may initially be mistaken for aging, poor condition, or chronic orthopedic disease.
Fortunately, day blooming jasmine poisoning is relatively uncommon because horses generally do not seek out the plant when adequate forage is available. Most cases occur after prolonged access to ornamental shrubs or naturalized stands during periods of limited grazing.
Common Names for Day Blooming Jasmine
Other names for day blooming jasmine include:
- Day jasmine
- Day jessamine
- Day-flowering jessamine
- Day-blooming cestrum
- Day cestrum
Table 1. Day blooming jasmine poisoning in horses at-a-glance
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| Risk Factors |
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Identification
Day blooming jasmine is an evergreen ornamental shrub that resembles a large, densely branched hedge. Although commonly called a jasmine, it is not a true jasmine. It belongs to the nightshade family (Solanaceae), which includes several plant species that are toxic to livestock. [1][2]
Flowers
Day blooming jasmine typically grows as a large, upright shrub with numerous erect, spreading branches that create a rounded, bushy appearance. Mature plants may reach several meters in height under favorable growing conditions.
The leaves are simple, alternate, smooth-edged, and lance-shaped to elliptical. They are dark green, somewhat glossy, and emit a distinctive pungent odor when crushed. [2][3][4]
Clusters of tubular flowers develop at the ends of branches and within the leaf axils. Individual flowers are approximately 1 inch (2.5 cm) long and white. Unlike closely related night blooming jasmine, whose flowers release their fragrance primarily after sunset, Cestrum diurnum flowers are fragrant during daylight hours, giving rise to the plant’s common name. [1][5][6]
After flowering, the plant produces small, spherical berries that are initially green and ripen to glossy black. Birds readily consume the ripe fruit and disperse the seeds, facilitating the shrub’s spread beyond cultivated landscapes into roadsides, fence rows, waste areas, unused pastures, and woodland edges. This natural seed dispersal explains why isolated plants may appear far from gardens or landscaped properties. [1][5][7]
Day blooming jasmine is native to the West Indies but has become widely established throughout warm regions of the world. In North America, it is most commonly encountered in southern Florida, the Florida Keys, southern Texas, and parts of California, although it is also cultivated elsewhere as a container or ornamental plant. [2]
Several ornamental Cestrum species closely resemble one another. Although accurate species identification may require botanical expertise, all members of the genus should be considered potentially hazardous. Several members of the genus cause poisoning, although the specific toxic effects vary considerably among species.
Day blooming jasmine is unusual because it causes chronic calcification of soft tissues, whereas several other Cestrum species primarily cause acute liver damage. [2][3][4]
What's your top priority with your horse's health?
What's your top priority with your horse's health?
Toxicology of Day Blooming Jasmine
Under normal circumstances, vitamin D plays an essential role in maintaining healthy bones and regulating calcium metabolism. Vitamin D obtained from the diet or produced in the skin is converted by the liver and kidneys into its active form, 1,25-dihydroxycholecalciferol (calcitriol). [2][5][7][8]
Production of this hormone is tightly controlled through a negative feedback system that responds to the body’s calcium and phosphorus requirements. When calcium concentrations are adequate, calcitriol production decreases, preventing excessive mineral absorption. [2][5][7][8]
Unlike many poisonous plants that contain irritants or neurotoxins, Cestrum diurnum owes its toxicity to a naturally occurring glycoside of calcitriol. Once ingested, this glycoside is hydrolyzed in the digestive tract, releasing a calcitriol-like compound that bypasses the body’s normal regulatory mechanisms. [2][5][7][8]
The plant-derived compound remains active regardless of the body’s normal feedback response. As a result, excessive amounts of calcium-binding proteins are produced in the intestine, significantly increasing absorption of calcium and phosphorus from the digestive tract. As calcium and phosphorus absorption increases, blood concentrations can rise, promoting mineral deposition in soft tissues. [3][7][8]
Persistently elevated calcium and phosphorus concentrations eventually cause widespread mineral deposition in tissues that are normally soft and flexible. This process is commonly referred to as metastatic or enzootic calcification.
Rather than strengthening the skeleton, excess calcium accumulates and hardens soft tissues, including: [7][8]
- Tendons
- Ligaments
- Major arteries
- Heart
- Lungs
- Kidneys
- Gastrointestinal tract
In horses, mineralization of the flexor tendons and suspensory ligaments is particularly significant. As these supporting structures become increasingly rigid, affected horses develop progressive stiffness, a shortened stride, and worsening lameness. Pain on palpation of the tendons and suspensory ligaments is common, and advanced cases may exhibit fetlock overextension, abnormal posture, or kyphosis (roach back). [7][8]
Unlike acute poisonings that develop within hours, day blooming jasmine toxicity requires repeated ingestion over an extended period. Horses generally consume the plant for several weeks or months before clinical signs become apparent. By the time obvious stiffness or weight loss develops, extensive tissue mineralization may already have occurred. [2][3][7]
Although blood calcium concentrations are typically elevated during active exposure, they may decline after horses are removed from the plant, even while irreversible mineral deposits remain in affected tissues. Consequently, clinical improvement often lags far behind removal from the toxic source, and some lesions may never fully resolve.
All parts of day blooming jasmine are considered toxic, although the leaves contain the highest concentrations of the calcinogenic compound. [2][5][7][8]
Symptoms of Day Blooming Jasmine Poisoning in Horses
Because poisoning develops gradually, early clinical signs may go unnoticed. Most horses continue eating normally while progressive mineralization slowly affects the musculoskeletal system and internal organs. As tissue damage advances, movement becomes increasingly uncomfortable, and chronic weight loss develops despite an apparently adequate appetite.
Clinical signs commonly progress over weeks to months and may include: [2][3][5][7][8]
- Weight loss despite a normal appetite
- Generalized stiffness
- Reluctance to move
- Lameness
- Short, choppy gait
- Pain affecting the flexor tendons and suspensory ligaments
- Increased urination (polyuria)
- Elevated heart rate
- Increased respiratory rate
- Recumbency in advanced cases
As calcification spreads to the cardiovascular system, lungs, kidneys, and other vital organs, affected horses become progressively debilitated. Death most commonly results from complications associated with heart failure, kidney failure, or an inability to rise after prolonged recumbency.
When to Call the Veterinarian
Seek veterinary evaluation if a horse has prolonged access to day blooming jasmine or other ornamental Cestrum species and develops: [5][7][8]
- Unexplained chronic weight loss
- Progressive stiffness
- Worsening lameness
Early intervention is particularly important because removing the horse from the toxic plant before extensive tissue mineralization develops offers the best opportunity to limit further progression.
Horses showing increasing reluctance to move, marked tendon pain, recumbency, or signs of cardiovascular or kidney dysfunction require immediate veterinary attention. Although no antidote exists, prompt diagnosis may prevent continued exposure and allow supportive treatment to begin before irreversible complications become more severe.
Exposure Risk Factors
Day blooming jasmine is primarily encountered in tropical and subtropical climates, where it is cultivated as an ornamental shrub or has escaped cultivation. In the United States, it is most commonly found in southern Florida, the Florida Keys, southern Texas, and parts of California.
Birds readily consume the berries and disperse the seeds, allowing the plant to become established along roadsides, fence lines, woodland edges, untended fields, and unmanaged pastures where horses may encounter it unexpectedly. [1][2]
Horses generally do not seek out day blooming jasmine when abundant, good-quality forage is available. Most poisonings occur when grazing options are limited or horses have unrestricted access to ornamental plantings. Curiosity, boredom, overgrazed pastures, or prolonged turnout in areas containing the shrub may increase the likelihood of repeated consumption.
Properties bordering residential gardens or landscaped equestrian facilities deserve particular attention. Although owners often recognize common pasture weeds, they may overlook hazardous ornamental shrubs. Garden waste also presents a potential risk if clippings or pruned branches are discarded where horses can reach them.
Not all Cestrum species cause the same form of poisoning. Although Cestrum diurnum is associated with chronic enzootic calcinosis, several closely related species primarily cause acute liver injury. Because these ornamental shrubs can appear very similar, all members of the genus should be considered potentially dangerous until they have been identified.
Diagnosis
Diagnosis of day blooming jasmine poisoning is based on a combination of exposure history, clinical signs, laboratory findings, and diagnostic imaging. Because the disease develops slowly, establishing that a horse has had prolonged access to the plant is often one of the most important diagnostic clues. [1][3][5]
Veterinarians typically investigate whether day blooming jasmine is present in the horse’s pasture, turnout area, or surrounding landscape. Ornamental shrubs growing along fence lines, in nearby gardens, or within unkept areas may help explain the horse’s progressive clinical signs. [3][5][7][8]
Physical examination commonly reveals chronic weight loss with varying degrees of stiffness and lameness. Pain on palpation of the flexor tendons and suspensory ligaments may reflect mineral deposition in these structures. More advanced cases may demonstrate reduced mobility, abnormal posture, or reluctance to walk. [1][3][5][8]
Routine bloodwork frequently identifies hypercalcemia during active exposure. Hyperphosphatemia may also be present, although phosphorus concentrations can vary with the stage of disease. [1][3][5]
As mineralization progresses, blood urea nitrogen (BUN) and creatinine concentrations may become elevated if kidney function is compromised. In some horses, calcium concentrations begin returning toward normal after removal from the plant despite continued progression of tissue mineralization, making laboratory results only one component of the overall diagnostic picture. [1][3][5]
Diagnostic imaging, particularly radiography (X-rays), may demonstrate abnormal mineralization of soft tissues and provide valuable evidence supporting the diagnosis. Calcification may be visible in tendons, ligaments, blood vessels, or other affected structures, depending on disease severity.
Imaging findings, together with the horse’s history and compatible laboratory abnormalities, help distinguish day blooming jasmine poisoning from other causes of chronic lameness or weight loss. [3][5][7]
Treatment & Management
There is no specific antidote for day blooming jasmine poisoning. Once mineralization of soft tissues has occurred, treatment focuses on preventing further exposure, managing clinical signs, and supporting affected organ systems. Because established calcification is only minimally reversible, early recognition offers the greatest opportunity to improve the long-term outcome. [1][3][5][8]
The first priority is to immediately remove the horse from all sources of the plant. Pastures, paddocks, and surrounding landscapes should be carefully inspected to prevent further exposure. Any ornamental shrubs accessible to horses should be fenced off or removed completely. [1][5][8]
Supportive care is tailored to the individual horse’s clinical condition. A high-quality diet and appropriate nursing care are recommended throughout recovery. Horses experiencing significant pain or reduced mobility require careful management to maintain comfort and minimize secondary complications associated with prolonged recumbency or reduced movement. [2][3][5][7][8]
Veterinarians may monitor blood calcium, phosphorus, and kidney function throughout treatment to assess disease progression and identify complications. Owners should remove supplemental vitamin D from their horse’s nutritional program, and unless specifically indicated for another medical condition, calcium-containing intravenous fluids should not be administered. [5][7][8]
Prognosis
The prognosis for horses with day blooming jasmine poisoning depends largely on how early the disease is recognized and the extent of soft tissue mineralization at diagnosis. Horses identified before extensive calcification develops may stabilize after removal from the plant, although recovery is often prolonged.
Once widespread mineralization affects the tendons, ligaments, blood vessels, kidneys, lungs, or cardiovascular system, the prognosis is poor. [1][3][5][8]
Although blood calcium concentrations may return to normal after exposure ends, mineral deposits resolve slowly and may never disappear completely. As a result, many horses continue to experience chronic stiffness, lameness, or reduced athletic ability after exposure has ceased. [1][3][8]
Severely affected horses may eventually develop heart failure, kidney failure, progressive debilitation, or permanent recumbency. In advanced cases, humane euthanasia may be the most appropriate welfare decision.
Long-term studies in other livestock species indicate that only limited regression of soft tissue mineralization occurs after removal from contaminated pasture, supporting the guarded outlook for advanced cases. [3][8]
Prevention
Preventing day blooming jasmine poisoning relies primarily on eliminating opportunities for prolonged exposure. Because the disease develops gradually over weeks or months, preventing repeated ingestion is considerably more effective than attempting to treat established soft tissue calcification.
Horse owners should routinely inspect their properties for ornamental shrubs that may pose a poisoning risk. Day blooming jasmine should never be planted within or adjacent to paddocks, pastures, or turnout areas. Existing plants should be fenced off or removed if horses can reach them.
Properties in tropical and subtropical regions should also be monitored for naturalized plants growing along fence lines, roadsides, woodland edges, or untended areas. Because birds readily disperse the seeds, new plants may become established even when none were intentionally planted on the property. Regular pasture inspections can help identify young shrubs before they become established.
Maintaining adequate pasture and providing sufficient high-quality forage reduces the likelihood that horses will investigate potentially toxic ornamental plants. Poisoning is more likely when grazing is limited or horses have little alternative forage available. Good pasture management is an important component of prevention.
Garden waste should never be discarded in horse enclosures. Owners, barn staff, landscapers, and maintenance personnel involved in maintaining equine properties should understand that ornamental plants can pose serious health risks to horses.
Although day blooming jasmine poisoning is relatively uncommon, its progressive nature and poor prognosis make prevention especially important. Removing toxic plants before horses are exposed is the most effective way to protect equine health and avoid the irreversible consequences of chronic soft tissue calcification.
Frequently Asked Questions
Here are some frequently asked questions about day blooming jasmine poisoning in horses:
Day blooming jasmine poisoning in horses is a progressive toxicosis caused by repeatedly eating the ornamental shrub Cestrum diurnum. The plant contains a calcitriol-like glycoside that disrupts calcium and phosphorus regulation, leading to hypercalcemia, hyperphosphatemia, and mineralization of soft tissues. This mineralization can damage tendons, ligaments, blood vessels, the heart, lungs, kidneys, and other organs over several weeks or months.
Day blooming jasmine can be identified as a large, densely branched evergreen shrub with dark green, slightly glossy leaves. It produces clusters of white, tubular flowers that are fragrant during the day, followed by small berries that turn from green to glossy black as they ripen. The leaves have smooth edges, range from lance-shaped to elliptic, and release a pungent odor when crushed. Because related Cestrum species can look similar and may also be toxic, uncertain plants should be treated as hazardous until positively identified.
All parts of day blooming jasmine are considered toxic to horses, although the leaves contain the highest concentrations of the harmful compound. Clippings and pruned branches can remain a risk if they are discarded where horses can reach them. Horses should also be kept away from the plant's flowers, stems, and berries.
Day blooming jasmine affects a horse's body by supplying an active vitamin D-like compound that bypasses normal calcium regulation. This causes excessive calcium and phosphorus absorption and eventually overwhelms the kidneys' ability to eliminate the excess minerals. Calcium then accumulates in normally flexible tissues, making tendons and ligaments rigid and interfering with the function of blood vessels and internal organs.
Day blooming jasmine poisoning usually develops after repeated ingestion over several weeks or months. Affected horses may continue eating normally while mineral deposits gradually form within their soft tissues. By the time weight loss, stiffness, or lameness becomes obvious, significant and potentially irreversible damage may already be present.
The signs of day blooming jasmine poisoning in horses commonly include weight loss despite a normal appetite, generalized stiffness, reluctance to move, lameness, and a short, choppy gait. Horses may also develop painful flexor tendons and suspensory ligaments, increased urination, and elevated heart and respiratory rates. Advanced cases can involve abnormal posture, severely reduced mobility, recumbency, heart failure, or kidney failure.
A veterinarian should be called when a horse develops unexplained chronic weight loss, progressive stiffness, or worsening lameness after possible access to day blooming jasmine or another Cestrum species. Increasing reluctance to move, marked tendon pain, abnormal urination, or reduced mobility requires prompt evaluation. A horse that becomes recumbent or shows signs of heart or kidney dysfunction needs immediate veterinary attention.
Day blooming jasmine poisoning is diagnosed using the horse's exposure history, clinical signs, laboratory testing, and diagnostic imaging. Bloodwork may reveal elevated calcium or phosphorus, while kidney values can become abnormal if renal function is affected. Radiographs may show mineral deposits within tendons, ligaments, blood vessels, or other soft tissues. Normalizing blood calcium after the horse is removed from the plant does not rule out poisoning because existing mineral deposits may remain.
There is no specific antidote for day blooming jasmine poisoning. Treatment begins with immediately preventing any further access to the plant and providing supportive veterinary care based on the horse's condition. Veterinarians may monitor calcium, phosphorus, and kidney function while managing pain, reduced mobility, and complications affecting internal organs. Established soft tissue mineralization is only minimally reversible, so early intervention is critical.
Horses can sometimes recover from day blooming jasmine poisoning when exposure is recognized before extensive soft tissue calcification develops. Improvement is often slow, and mineral deposits within tendons, ligaments, blood vessels, and internal organs may never fully disappear. Some horses remain chronically stiff, lame, or unable to return to their previous level of athletic work. Horses with extensive heart, lung, or kidney involvement generally have a poor prognosis.
If day blooming jasmine is growing near horses, access to the plant should be blocked immediately. The shrub should be securely fenced off or removed, and all cuttings, fallen branches, and garden waste should be disposed of where horses cannot reach them. Nearby fence lines, roadsides, woodland edges, and neglected areas should also be inspected for additional plants spread by birds.
Day blooming jasmine poisoning can be prevented by eliminating horses' access to the plant and regularly inspecting their surroundings for new growth. The shrub should never be planted in or beside paddocks, pastures, or turnout areas, and existing plants should be fenced off or removed. Providing adequate pasture and good-quality forage can reduce browsing caused by hunger or limited grazing. Owners, barn staff, landscapers, and maintenance workers should also be instructed never to discard ornamental plant material in horse enclosures.
Summary
Day blooming jasmine poisoning is a progressive toxicosis caused by repeated ingestion of Cestrum diurnum. Its vitamin D-like toxin promotes irreversible mineral deposition in soft tissues, leading to lameness, organ dysfunction, and potentially death.
- Day blooming jasmine is an evergreen ornamental shrub with white tubular flowers and glossy black berries
- Repeated ingestion disrupts calcium and phosphorus regulation, causing mineral deposits in tendons, ligaments, blood vessels, and internal organs
- Clinical signs include weight loss despite a normal appetite, generalized stiffness, progressive lameness, tendon pain, and reluctance to move
- Treatment requires immediate removal from the plant, supportive care, pain management, and monitoring of calcium, phosphorus, and kidney function
- Preventing access to shrubs, naturalized plants, and discarded garden waste is essential because established mineralization may never fully resolve
References
- Guide to Poisonous Plants. Colorado State University.
- Burrows. G. E. Toxic Plants of North America. John Wiley & Sons. 2013.
- Plumlee. K. H. Ed. Clinical Veterinary Toxicology. Mosby. 2004.
- Gupta. R. C. Veterinary Toxicology: Basic and Clinical Principles. Elsevier Academic Press. 2012.
- Waldridge. B. M. Ed. Nutritional Management of Equine Diseases and Special Cases. Wiley. 2017.
- McQuinn. S. Horse Owner's Guide to Toxic Plants. Skyhorse Publishing. 1996.
- Reed. S. M. et al. Equine Internal Medicine. Saunders Elsevier. 2010.
- Hovda. L. R. Blackwell's Five-Minute Veterinary Consult Clinical Companion Equine Toxicology. Wiley Blackwell. 2022.
