What is Fescue Toxicity ?
Fescue is a type of plant native to many regions. It is safe for your horse to consume, unless it is contaminated by the fungus known as Acremonium coenophialum. This fungus grows and lives in contaminated fescue and when ingested by your horse, toxicity will develop. The toxin produced by the fungus inhibits some very important hormones from being produced properly in a pregnant mare. This leads to problems during birth and when the foal is trying to feed. There are not very many treatments out there for fescue toxicity, and the treatments veterinarians are employing are not guaranteed to work. Prevention and eradication of growth of toxic fescue are important.
Fescue toxicity typically affects pregnant mares. If you believe yours is not doing well with her pregnancy or have noticed any abnormal symptoms, contact your veterinarian.
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Symptoms of Fescue Toxicity in Horses
Symptoms of fescue toxicity may include:
- Overall reduced performance
- Sloughing off of the end of the tail
- Poor weight gai
- Increased respiration rate
- Rough coat
- Excessive salivation
- Lower prolactin levels in the serum
- Lower reproductive performance
- Difficult birthing
- Lactation related issues
The severity of fescue toxicity can vary in each case. It can vary in every field and can change from year to year. If temperatures are above 75 degrees fahrenheit and if a high nitrogen fertilizer has been applied to the field, it will also increase the severity of the toxicity.
Causes of Fescue Toxicity in Horses
Fescue toxicity is caused by the fungus known as Acremonium coenophialum growing within the fescue plant. This fungus produces toxins that prevent prolactin which is essential for milk let down in pregnant mares. There is however, some fescue that can be found without the fungus that is safe to give to your mare.
Diagnosis of Fescue Toxicity in Horses
In typical cases of fescue toxicity, it can be identified by the veterinarian from clinical symptoms alone. Also, if there is fescue in the pasture your horses have been in, you can send samples to the laboratory for testing for the presence of the fungus.
However, if you do not know what is in your pasture and neither does your veterinarian, it may take further diagnostics to rule out other probable causes. The veterinarian may want to start with blood work for an evaluation of your horse’s organ function and blood levels. A complete blood count (CBC) and chemistry panel will give her the needed information to properly evaluate the severity of your horse’s condition.
If your horse is pregnant, she may want to palpate the fetus to check how he is growing. She will rectally palpate your mare to check the size and positioning of the foal. In addition to this, she may want to do an ultrasound to obtain an actual live image of your horse and the foal. Depending on your horse’s condition, the veterinarian may want to run further diagnostics for a more thorough assessment.
Treatment of Fescue Toxicity in Horses
Treatment is almost non-existent in cases of fescue toxicity. It has been said a drug known as domperidone has shown some signs of counteracting the negative side effects of toxicity in mares. It is also believed a certain seaweed product is able to lessen immunosuppressive effects of toxic fescue. Also, if you remove your pregnant horse from the suspected pasture at least one month prior to giving birth, it can reduce and maybe prevent parturition and lactation related issues.
Since there isn’t much in the form of actual treatment, prevention becomes the ultimate treatment. Prevention of fescue toxicity includes destroying infected grasses and fields with controlled burns, mixing in other grasses or legumes into fescue fields will help to dilute it, and utilization of specific fertilizing programs. Some horse owners are even going to the extent of ridding themselves of the fescue and then replanting the field with some type of choke plant. This means the plant is very aggressive and does not allow other vegetation to grow in the area and will even out compete and take over the other plants.
Recovery of Fescue Toxicity in Horses
The severity of the fescue toxicity will affect your horse’s recovery. If you did not seek veterinarian attention or did not realize your pregnant mare was in a contaminated field, she may have a stillbirth or not be able to provide colostrum and then milk for her foal. If you caught the problem early on, removed her from the field, gave medication if needed as instructed, prognosis of her birthing a healthy foal is good.
As a horse owner, educate yourself on what your horse is eating. Even if they are just grazing on the natural vegetation of the area, there is no guarantee it is healthy for them. If you are new to the field and have questions, do not hesitate to discuss it with your veterinarian. She will be happy to help you as you ensure the health of your horse.
Fescue Toxicity Questions and Advice from Veterinary Professionals
I have a miniature mare that is 343 days in foal, her last delivery date was 336, she is a new mare to me. A neighbor gave us some pasture , we live in Valley Springs, Ca am concerned about fescue grass does it grow in our area? And if so how much would the mare need to eat to harm the foal? She is 15yrs old her former owner said she foals out easily and is an easy keeper, am just worried about her. And of course the foal.
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