Migrating Grass Awns (Foxtails) in Horses: Symptoms, Treatment & Prevention

Grass Awns
Migration
Symptoms
Diagnosis
Treatment
Prevention

Grass awns, commonly referred to as foxtails, pose a significant health risk to horses and other grazing animals. Horses grazing in areas with foxtail can inadvertently eat or inhale the awns, or they can become embedded in the horse’s ears, nose, or skin.

The barbs on the awns make them difficult to remove, and they tend to “migrate” through the horse’s body, travelling deeper into tissues. Once embedded, they can lead to inflammation, infections, and potentially life-threatening complications.

Signs of migrating grass awns in horses are variable depending on the affected area. Symptoms can include swelling or redness, skin irritation, coughing, nasal discharge, drooling or difficulty chewing.

Robust pasture management is key to preventing migrating foxtails in horses. Identifying and removing hazardous grass species reduces the risk of foxtail injuries and infections, ensuring pastures remain safe for your horse.

Dangers of Grass Awns in Horses

Grass awns are the seed heads of certain grass species, such as foxtails (genus Alopecurus and Setaria spp.) and other related plants.

Grass seeds that can potentially become migrating foxtails in horses include: ^[1]^[2]

Bromegrasses (Bromus spp.)
Speargrass (Stipa spp.)
Wild oats (Avena fatua)
Feather finger grass (Chloris virgata)
Barnyard grass (Echinochloa spp.)
Wild barley and foxtail barley (Hordeum spp.)
Bent grass (Agrostis spp.)
Windgrass (Apera spp.)

These seeds are equipped with barbed structures, a unique adaptation that aids their dispersal. These barbs catch onto the fur, clothing, or skin of passing horses, animals and humans, allowing the seeds to anchor and spread more effectively.

In addition, the external structures of the awn can change shape depending on humidity levels, allowing the seeds to burrow into the soil on their own, which increases their chances of germination. ^[1]

This same burrowing action is what makes grass awns a hazard for horses and other outdoor animals, as the foxtails burrow deeper into the soft tissue once they have penetrated the skin or orifices.

Foxtails are most commonly found in dry, grassy areas, particularly during the late spring and summer months. The slender, pointed seeds have backward-facing barbs that easily embed in a horse’s skin or mucous membranes, where they can cause infection and other significant problems if not promptly removed. ^[2]

Grass Awns Migration

Grass awns are not toxic; it is their barbs that make them dangerous to horses. Once they embed in the skin or mucous membranes, the barbs prevent the awns from being expelled. In movement similar to how they burrow into the earth, the awns migrate deeper into tissues, a process that is amplified by the horse’s own movement and muscle contractions. ^[3]

Migration can cause significant mechanical damage as the awns tear through tissue, leading to inflammation and creating pathways for secondary bacterial infections.

Grass awns can carry bacteria into the body, leading to infections that can be difficult to treat. In some cases, abscesses can form around the awn, which can become chronic and resistant to standard treatments. ^[3]

Grass awns may enter a horse’s body through multiple routes, each presenting its own set of challenges. Common sites of entry include: ^[3]^[4]

Mouth: Horses grazing in pastures that contain foxtails can inadvertently eat grass awns. Once in the mouth, the awns can embed in the gums, tongue, or cheeks, leading to oral discomfort and potential infection.
Nostrils: When inhaled, awns can get lodged in the nasal passages, sinuses, or even reach the lungs, causing respiratory distress. As a wind dispersal adaptation, foxtails may float in the air above the ground, even if livestock are not actively grazing them.
Eyes: Equine eyes are particularly vulnerable to grass awns. Since the horse’s eyes protrude from the head, they are more exposed. Sharp foxtail seeds can cause severe irritation, conjunctivitis, and corneal ulcers.
Ears: Grass awns can enter the ears, causing discomfort, head shaking, ear scratching, and potentially leading to infections.
Skin: Grass awns can penetrate the skin, particularly in areas over soft tissue. Once embedded, they can migrate through the skin and subcutaneous tissues, causing significant pain and deeper infections which can become severe.

Symptoms

The clinical signs of grass awn injuries in horses vary depending on the site of entry and the extent of migration, and whether infection takes hold.

External signs may include: ^[5]

Swelling and redness: These are common indicators of an awn’s entry point, particularly if the awn has caused an infection or abscess. The area may be warm to the touch and sensitive, with visible swelling.
Discharge: Pus or other discharges from a wound or natural orifice may indicate the presence of a grass awn. The discharge may be persistent, and the wound may not heal despite treatment.
Puncture wounds: A small, puncture-like wound may be visible at the site where the awn entered the body. These wounds are often difficult to detect, especially if they are located in areas with thick fur or in less visible regions of the body.
Irritation: Horses with a migrating grass awn may show signs of discomfort and irritation at the site of migration, including pawing, scratching, and rubbing around the ears, nose, or mouth.

Respiratory Signs

If inhaled, grass awns can cause a range of respiratory symptoms in horses, depending on their location within the respiratory tract.

Symptoms may include: ^[6]

Coughing: A persistent cough may develop if the awn is lodged in the nasal passages, sinuses, or trachea. The cough may be dry or productive, depending on the extent of inflammation and if infection is present.
Nasal discharge: Horses with grass awns in their nasal passages or sinuses may exhibit unilateral or bilateral nasal discharge. The discharge may be clear, purulent, or bloody, depending on the severity of irritation and the presence of secondary infections.
Respiratory difficulties: In severe cases, the horse may exhibit signs of respiratory distress, such as labored breathing, flaring nostrils, and increased respiratory rate. These symptoms are often associated with grass awns that have migrated into the horse’s trachea, causing an obstruction.

Oral & Gastrointestinal Signs

Grass awns lodged in the mouth or gastrointestinal tract can cause significant discomfort and lead to various symptoms, including: ^[7]^[8]

Drooling: Excessive drooling is a common sign of oral discomfort and may indicate the presence of grass awns embedded in the horse’s gums.
Difficulty eating: Horses with awns lodged in their gums, tongue, or cheeks may have difficulty eating due to pain and discomfort. Reduced intake of feed can lead to weight loss and poor body and coat conditions. In some cases, affected horses may exhibit signs of pain when chewing or swallowing (e.g., only chewing on one side).
Gastrointestinal distress: If ingested, grass awns can cause gastrointestinal upset, including colic, diarrhea, or constipation. In some cases, the awn may penetrate the intestinal wall, leading to peritonitis or other severe complications.

Ocular Signs

If a grass awn enters a horse’s eye, it can cause significant distress and irritation. ^[7]

Signs and complications include: ^[7]

Excessive tearing
Corneal ulcers
Rubbing/pawing at eyes
Redness in the eyes (conjunctivitis)
Keeping one eye closed
Vision changes

Any obvious or suspected eye or vision disorder is considered a medical emergency. Urgent veterinary intervention provides the best chance of preserving vision.

Diagnosis

Diagnosing injuries related to migrating grass awns can be challenging, especially if a puncture wound is not obvious.

The first step in the diagnostic process is a thorough physical examination and medical history of the horse. Diagnostic imaging is often necessary to locate grass awns that have migrated internally. Depending on the suspected location of the awn, various imaging modalities may be used, including: ^[5]

Ultrasonography
Endoscopy – passing a camera through the mouth, ear, or nostril

In cases in which the embedded grass awn leads to infections and inflammation, veterinarians may require specific laboratory tests including: ^[5]

Bacterial cultures: Cultures from abscesses or discharging wounds can help identify the specific bacteria responsible for the infection, indicating the appropriate antibiotic treatment.
Blood tests: May reveal signs of systemic inflammation or infection (e.g., elevated white blood cell count).

If you suspect your horse is affected by migrating foxtails or any other medical condition, consult with your veterinarian to obtain an accurate diagnosis.

Treatment

The first step in treatment is removing the grass awn(s) once located. Early identification and removal are essential in preventing further migration and complications such as bacterial infections.

The method of removal depends on the location and extent of the awn’s migration within the horse’s body: ^[8]

Superficial Awns: Awns that are lodged in superficial tissues or visible areas, such as the skin or gums, may be removed manually using instruments such as forceps. Local anesthesia may be administered to minimize discomfort during the procedure.
Migrated Awns: Awns that have migrated deep into tissues or are located in less accessible areas may require surgical intervention. Once the awn is removed, the surrounding tissues need to be thoroughly cleaned to remove any dead, damaged, or infected tissue (debridement) to reduce the risk of infection.

Secondary Infection Management

If the horse develops a secondary bacterial infection due to migration of the awn, they often require treatment with antibiotics. The choice of antibiotic depends on the specific bacteria identified through culture. In some cases, broad-spectrum antibiotics can be used initially, then followed by targeted antibiotic therapy based on culture test results. ^[5]

Horses that develop abscesses often require drainage to remove accumulated pus and reduce the amount of bacteria present. Drainage can be carried out through surgical means or by the insertion of drainage tracts. Following drainage, regular wound care is crucial in promoting healing and preventing the recurrence of infection. ^[5]

Supportive Care

Alongside the removal of the awn and antibiotic treatment, affected horses require supportive care to ensure their recovery.

Options may include: ^[5]

Pain management: Non-steroidal anti-inflammatory drugs (NSAIDs) or other pain-relieving medications may be prescribed to manage pain and reduce inflammation.
Rest or controlled exercise: Horses recovering from infection may not be able to perform until the infection is cleared.
Monitoring: Caretakers should keep a close eye on horses as they recover from injury and infection, to ensure treatment is effective. In severe cases, veterinarians may recommend follow up assessment.

Prognosis

The prognosis for foxtails embedded in the mouth is generally good, as long as the horse is treated promptly and access to the presumed source (whether hay or pasture) is removed. ^[5]

Foxtails embedded in or around the eye may have a poorer prognosis, depending on the extent of damage to the ocular structures by the migrating awn. Cases where foxtails have injured the digestive tract may need more aggressive treatment, but the prognosis is good. ^[5]

Prevention

Given that horses are outdoor grazing animals, it may not be possible to prevent all grass awn migration injuries. However, there are steps owners and caretakers can take to minimize the risk, particularly around pasture and grazing management.

Effective pasture management is one of the most important strategies for preventing grass awn-related issues. By reducing the growth of foxtails and other grass species with awns, the risk of exposure can be minimized.

Key pasture management practices include: ^[2]

Regular mowing: Regular mowing of pastures can help prevent foxtails from reaching maturity and producing seeds. Keeping grass short reduces the likelihood that horses will come into contact with mature seed heads. Note that mowing alone will not resolve the issue; mowing at incorrect times can actually increase the risk of horses coming into contact with awns.
Weed control: Implementing weed control measures, such as herbicide application or manual removal of foxtail plants, can reduce the presence of grass awns in pastures. Work with a qualified professional if you are considering using herbicides on feeding pastures.
Pasture rotation: Rotating pastures to allow for regrowth and prevent overgrazing can help maintain healthy pasture conditions and reduce the spread of foxtails.

Alongside pasture management, grazing management of other forages can help prevent migrating grass awns. Always inspect incoming hay for hazards like mold and grass awns before offering it as forage. Ensure hay is stored properly and sourced from a reputable producer.

Inspecting bedding, particularly straw, before use is also advised to prevent migrating foxtails.

Summary

Migrating grass awns (foxtails) present a serious health risk for horses, capable of causing significant discomfort and potentially life-threatening conditions.

The barbed nature of these seeds allows them to penetrate the skin or mucous membranes and migrate through tissues, leading to inflammation, infections, and abscesses.
Early detection, prompt removal, and appropriate treatment are essential to prevent complications associated with grass awns.
Prevention strategies, including effective pasture and lifestyle management can reduce the risk of grass awn migration injuries in horses.