Locoweed is a common name for several species of toxic plants in the Astragalus and Oxytropis genera. These plants contain swainsonine, a toxic alkaloid that affects the nervous system of grazing animals such as cattle, horses, and sheep.
In this topic, we will explore what locoweed is, where it grows, why it is dangerous, and how it affects animals.
What Is Locoweed?
Locoweed refers to various species of leguminous plants found primarily in North America, especially in the western United States and Mexico. It thrives in dry, open rangelands and is often consumed by animals when other forage is scarce.
The name “locoweed” comes from the Spanish word “loco,” meaning crazy, due to its effects on animal behavior.
Characteristics of Locoweed
- Scientific Classification: Belongs to the Astragalus and Oxytropis genera.
- Appearance: Small shrubs or herbaceous plants with purple, pink, white, or yellow flowers.
- Growth Areas: Found in high-altitude grasslands, deserts, and dry plains.
- Toxicity: Contains swainsonine, a neurotoxin affecting livestock.
Why Is Locoweed Dangerous?
Locoweed is toxic due to swainsonine, which disrupts cellular function by interfering with the body’s ability to break down sugars. This toxin accumulates in the body and leads to neurological and physiological disorders.
Factors That Make Locoweed Harmful
- High Toxicity – Even small amounts can cause serious damage over time.
- Addictive to Animals – Some animals develop a craving for locoweed and continue eating it even when better forage is available.
- Cumulative Effects – The toxin builds up in the system, leading to progressive damage.
How Does Locoweed Affect Animals?
1. Neurological Symptoms
The most noticeable effect of locoweed poisoning is on an animal’s nervous system. Swainsonine disrupts normal brain function, leading to erratic behavior and loss of coordination.
Common Neurological Symptoms
- Staggering or difficulty walking
- Tremors and muscle weakness
- Unusual aggression or extreme lethargy
- Head shaking and strange facial expressions
Horses, in particular, exhibit “loco” behavior, which includes unpredictable movements, jumping, and even attacking objects.
2. Weight Loss and Weakness
Animals that consume locoweed often experience loss of appetite and weight loss. This occurs because the toxin affects metabolism, preventing the body from properly utilizing nutrients.
Signs of Physical Weakness
- Reduced muscle mass
- Low energy levels
- Difficulty standing or moving
- Hollowed appearance due to loss of body fat
Livestock that eat locoweed for prolonged periods become too weak to graze, making them susceptible to starvation and predators.
3. Reproductive Problems
Locoweed poisoning can also impact reproductive health in livestock. The toxin affects hormone regulation and fetal development, leading to complications.
Reproductive Effects of Locoweed
- Miscarriages or stillbirths in pregnant animals
- Birth defects in newborns
- Reduced fertility in both males and females
Ranchers often see low birth rates in herds that graze on land where locoweed is abundant.
4. Organ Damage
Chronic exposure to locoweed can damage multiple organs, especially the liver, heart, and kidneys. The toxin interferes with cell function, leading to long-term health issues.
Signs of Organ Damage
- Swelling or bloating due to fluid retention
- Jaundice (yellowing of the skin and eyes)
- Irregular heartbeats or difficulty breathing
- Poor digestion and diarrhea
In severe cases, multi-organ failure can occur, resulting in death.
Which Animals Are Most Affected?
Different animals react to locoweed poisoning in varying ways, but livestock are the most vulnerable due to their grazing habits.
Animals Commonly Affected by Locoweed
| Animal | Symptoms | Severity |
|---|---|---|
| Horses | Severe neurological symptoms, unpredictable behavior, muscle tremors | Very High |
| Cattle | Weight loss, poor reproduction, lethargy, occasional nervous symptoms | High |
| Sheep & Goats | Weight loss, mild neurological issues, reproductive problems | Moderate |
| Deer & Wildlife | Occasional poisoning, but less common due to varied diets | Low |
Horses are most sensitive to locoweed, while cattle and sheep show gradual health decline over time.
How to Prevent Locoweed Poisoning in Livestock
1. Remove Locoweed from Pastures
- Identify and remove locoweed manually or use herbicides.
- Rotate pastures to avoid overgrazing, which forces animals to eat toxic plants.
2. Provide Nutrient-Rich Forage
- Ensure that livestock have access to high-quality hay and grains.
- Supplement their diet with essential minerals to discourage locoweed consumption.
3. Monitor Livestock for Early Signs of Poisoning
- Watch for behavioral changes or weight loss.
- Conduct regular veterinary health checks.
4. Isolate Affected Animals
- If an animal shows signs of poisoning, remove it from pasture to prevent further consumption.
- Provide supportive care such as hydration and nutrient supplements.
Treatment Options for Locoweed Poisoning
Currently, there is no antidote for locoweed poisoning. However, early intervention can help animals recover before irreversible damage occurs.
Supportive Treatments
- Remove access to locoweed immediately.
- Provide a high-protein diet to support metabolism.
- Administer fluids and electrolytes to combat dehydration.
- Allow rest and observation to monitor recovery progress.
Horses and cattle that have consumed large amounts of locoweed may suffer from permanent brain damage, making prevention the best strategy.
Locoweed is a highly toxic plant that poses serious risks to grazing animals. Its effects range from neurological disorders and weight loss to reproductive failure and organ damage.
Ranchers and livestock owners must take preventative measures such as pasture management, dietary supplementation, and early detection of symptoms to protect their herds.
By understanding what locoweed is and how it affects animals, farmers can ensure the health and safety of their livestock while minimizing economic losses.