Placentitis And Mycotoxins

Mycotoxins are harmful secondary compounds produced by molds that are found in soil and vegetable matter including grains, forages and feed. They can be formed in the field both before and during harvest, and can continue to be formed under suboptimal storage conditions after harvest.


Mycotoxins have been implicated with various horse health problems, including decreased appetite, colic, abnormal liver function, hypersensitivity, neurological disorder, and brain lesions.

Long term exposure of horses to low levels of mycotoxins may result in immune suppression, reduced growth rate, impaired feed conversion, more fertility problems, frequent respiratory problems, reduced performance, and higher incidence of laminitis. In most cases these problems are considered to be caused by reasons other than mycotoxins.


Hence, mycotoxins often are not recognized as the real trigger or at least as an important co-factor in the incidence of these conditions. Initially, mycotoxins cause non-acute problems in horses. The impact on health and reduction of performance may be negligible. But as exposure time increases effects on performance and health become more pronounced. Researchers studying the incidence of colic and mycotoxin contaminated feed found that some degree of mycotoxin contamination occurred in every case of colic. But also reduced fertility/conception rates may be evidence of mycotoxin consumption due to the sensitivity of horses to the mycotoxin zearalenone.


The effects of mycotoxins in horses can be amplified by performance and production stresses. Sport horses in training and competition, breeding mares and stallions, and rapidly growing foals are more susceptible to mycotoxins than horses used for less rigorous recreational riding or just being stabled. Their immune competency may be compromised, their nutritional requirements may not be fully met and they consume more concentrates.


Horses can be exposed to mycotoxins by eating contaminated feed ingredients such as concentrates (i.e., grains and protein supplements), whole grains, hay, and green pasture--essentially any feed ingredient. Respiratory and/or dermal (skin) entry of mycotoxins can also occur, but these routes are of less significance. The extent of mycotoxin exposure depends on how much of the contaminated ingredient is fed, and the mycotoxin concentrations present in the feed. Any feed ingredient can contain multiple mycotoxins, which will likely interact and become more toxic than they would be separately.


How do we know if horses are exposed to mycotoxins? Diagnosing mycotoxicoses is a big challenge in any species because of the lack of mycotoxin-specific clinical signs for majority of mycotoxins. Signs such as lowered feed intake, leg problems, nervous system problems, and increased mortality can also be caused by many other factors. To help confirm a diagnosis of mycotoxicosis, test suspect horse feed / ingredients for molds and mycotoxins using reliable, accredited laboratories. Sampling might not pick up a moldy area of feed (i.e., the whole batch of hay/feed might not be contaminated), but the analysis can provide valuable information.



What are the effects of molds and mycotoxins on horses? 

  • Skin allergies and inflammation

  • Respiratory blockage

  • Respiratory diseases- Chronic obstructive pulmonary disease (COPD, also called heaves)


  1. Mycotoxins: 

  • Aflatoxins (predominantly found in corn, soybean meal, alfalfa pellets): ataxia (incoordination), tremors, fever, anorexia, loss of appetite, weight loss, icterus (yellowing of the eye or skin), hemorrhages, bloody feces, brown urine, and death

  • Ochratoxins (mostly found in corn, wheat, oats, rye, barley, hay/straw, grass): kidney damage

  • Deoxynivalenol (DON) and T-2 toxin (mostly found in corn, wheat, oats, rye, barley): reduced feed intake, weight loss in exercising horses, liver damage, reduced immunity

  • Fumonisins (mostly found in corn, wheat, oats, rye, barley): very toxic to horses; equine leukoencephalomalacia (commonly known as moldy corn poisoning), depression, abnormal behavior, head pressing, ataxia, staggers, stupor, lameness, seizure and death; survivors will have some degree of permanent neurological disorder

  • Zearalenone (mostly found in corn, wheat, oats, rye, barley, hay/straw, grass): vaginal prolapse, abortions, uterine and internal hemorrhage, severe flaccidity of male genitalia

  • Ergot alkaloids (mostly found in wheat, oats, rye, barley, hay/straw, grass): extended gestation length, agalactia (no milk production), red bag placentas, fetal losses, dead foals

How can you prevent mycotoxicoses in horses? There is no magic bullet for mycotoxin prevention. Preventive programs have to be applied at different levels of crop production (field production, harvesting, and storage of feed ingredients), feed production (feed mills) and animal production (farms). Check bedding – if horses are stabled on straw, there is a chance that this is contaminated with mycotoxins, in particular DON. Hay baled with a moisture content of more than 15% is more likely to develop mold, giving way to a mycotoxin proliferation. Mow pastures to prevent them obtaining seed heads. 


Post-harvest control: Mold growth can be controlled by storing feed materials at optimal conditions. 

·       Dry grains to below 13% moisture and maintain that moisture level during storage.

·       Use effective mold inhibitors if grains/concentrates are stored at more than 13% moisture.

·       Maintain optimal temperature, humidity, and ventilation for crop storage.

·       In case of hay or silage, inadequate packing, improper coverage and suboptimal face management (not keeping the silage surface smooth and packed to minimize the product's air exposure) can lead to excess aeration within the hay/silo, promoting the growth of molds and subsequent mycotoxin production.


Mycotoxin control in the horse: Despite feed producers' best efforts, mycotoxins can still end up in horse feed and forages. To decrease the harmful effects of these mycotoxins in animals, organic and inorganic adsorbents or binders (which bind to the mycotoxins so the animal's system can't absorb them) can be added to feed. Following are a few points to remember about mycotoxin binders:

·       Binders are more effective if applied at the time of feed production, but they can also be added to the horse's daily feed by the owners.

·       Ideal mycotoxin binders should bind multiple mycotoxins at low dosages and should have strong peer-reviewed research support (which should be available from the manufacturers upon request).

At Spurwing Horse Feeds we incorporate a mycotoxin binder in every feed to reduce the incidence of mycotoxins. We also adhere to strict storage protocol for raw materials.