Even though cows’ digestive system is more complicated than monogastrics’—they can degrade some mycotoxins in the rumen—and cattle are still affected by mycotoxins. Interestingly, the rumen’s ability to degrade some mycotoxins into harmless molecules is its ability to degrade other mycotoxins into even more toxic metabolites.
Endotoxins
Fumonisin
Deoxynivalenol
Aflatoxin
Ergot
Fumonisin
Aflatoxin
Fumonisin
Fumonisin
Deoxynivalenol
T-2 toxin
Zearalenone
Ochratoxin
Ergot
Ergot
Endotoxins
Fumonisin
Deoxynivalenol
Aflatoxin
Ergot
Fumonisin
Aflatoxin
Fumonisin
Fumonisin
Deoxynivalenol
T-2 toxin
Zearalenone
Ochratoxin
Ergot
Ergot
In addition to contaminated grain, improperly managed silage promotes the production of molds and mycotoxins. When considering the total mixed ration (TMR), even low levels of mycotoxins in the grain can reach harmful levels when mixed with contaminated forage. It is important to remember that mycotoxicosis will vary depending on the type of mycotoxin, quantity, age of the animal, time of exposure, direct and indirect interactions, and, of course, the nutrition and health status of the animal.
| Endotoxins | FUM | ZEA | DON | T-2 | OTA | AFLA | Ergot | |
|---|---|---|---|---|---|---|---|---|
| Decrease milk production | ++ | ++ | ++ | ++ | ++ | |||
| Anorexia | + | ++ | + | + | ||||
| Growth retardation | ++ | + | ++ | + | ||||
| Hepatic lesion | ++ | + | + | |||||
| Kidney damage | + | |||||||
| Pulmonary Edema | +++ | |||||||
| Heart damage | ++ | |||||||
| Abortion | ++ | |||||||
| Infertility | +++ | |||||||
| Vulvovaginitis | +++ | |||||||
| Gangrene | +++ | |||||||
| Immunosuppression | ++ | +++ | + | ++ | +++ | + | +++ | ++ |
| Table: Clinical signs and lesions observed in ruminants |
There is growing knowledge about the role of endotoxins in the etiopathology of multiple periparturient diseases of dairy cows: laminitis, retained placenta, metritis/endometritis, fatty liver, displaced abomasum, and milk fever. However, take into account that these conditions are multifactorial.
One common feeding disorder in dairy cows is subacute rumen acidosis (SARA). SARA is regularly used as a synonym for poor rumen health and is defined as “a threshold of 180 min/day below pH 5.6” (Plaizier et al., 2017). A low pH in the rumen causes a decrease in bacteria richness and an increase in gram-negative bacteria populations. Pyrogenic lipopolysaccharides (LPS) are released as a result of the increased gram-negative bacterial growth rate or due to the acidity, which makes bacteria more prone to lysis/rupture. Therefore, a higher concentration of free LPS is detected in the rumen fluid of cows experiencing SARA. Also known as endotoxins, LPS may contribute to SARA since it can stimulate the growth of acidosis-related bacteria to create a vicious circle.
Fumonisin B1 is a toxic compound that can harm beef and dairy cattle. It acts as an immunosuppressant, reduces lipid metabolism, and can cause hepatic and lung damage. Fumonisin B1 also reduces milk production in dairy cattle. The toxin affects young cattle the most, but prolonged exposure can harm any animal. To prevent contamination, producers should monitor feed sources and use alternative feed or additives to protect against the harmful effects of fumonisin B1.
Trichothecenes are a group of mycotoxins that can have a significant impact on the health of cattle. While they share a similar structural makeup, trichothecenes can vary in origin fungus and impact based on individual animal traits.
Trichothecenes primarily affect the central nervous system’s regulation of appetite control, increase amino acids circulating in the blood, and raise tryptophan levels in the brain to boost serotonin levels. High serotonin levels produce the perception of satiety, which can impact feed intake. Additionally, trichothecenes can inhibit protein synthesis in the liver, leading to the buildup of reactive oxygen species and oxidative stress in cells. This can ultimately trigger programmed cell death pathways and impact actively proliferating cells such as those in the gastrointestinal tract or bone marrow.
Two specific types of trichothecenes, T-2 and HT-2, can cause significant digestive system damage in cattle. They can lead to feed rejection, gastric and intestinal hemorrhages, and even rumen perforations, which ultimately decrease milk production and trigger an immune response.
Another type of trichothecene, DON, can alter rumen fermentation and reduce the digestibility of utilizable protein, ultimately leading to decreased feed intake, lower milk production, and decreased fat content. DON can also impact reproductive efficiency and increase somatic cell counts in milk, making it particularly problematic for dairy cattle.
Zearalenone (ZEA) is a potent mycotoxin that can have a significant impact on the reproductive system of cattle. ZEA works by stimulating estrogen receptors, which can lead to a range of negative health outcomes.
One of the most significant impacts of ZEA is a decrease in fertility, which can lead to delays in the return to heat, lower conception rates, and reduced births per cow. ZEA exposure has also been linked to a higher incidence of noninfectious abortion, which can significantly impact herd health and productivity. Additionally, ZEA can reduce bull fertility, further compounding the negative impacts on reproductive outcomes.
Given the significant impact of ZEA on cattle reproductive health, it is often considered one of the most important mycotoxins affecting farms today. The economic losses associated with ZEA exposure can be substantial.
Penicillium is a type of fungus that can be found on a dairy farm in various places, such as in the soil, feedstuffs, and bedding materials. It can grow and multiply under certain conditions, such as high humidity and warm temperatures, and can contaminate the feed and forage sources used to feed dairy cattle.
One of the most common forms of penicillium contamination on a dairy farm is Penicillium roqueforti, which can grow on and contaminate silage. If ingested, it can lead to increased capillary permeability and damage to organs such as the lungs, heart, liver, and kidneys, which can result in reduced milk production and potentially premature culling of the affected animals.
Aflatoxin is a well-known immunosuppressant that can decrease feed consumption in cattle. This reduction in energy availability and weakened immune system can make cows more susceptible to diseases caused by other pathogenic organisms. Hepatotoxicity, or liver damage, is a common ailment associated with aflatoxin exposure. Not only does aflatoxin reduce milk production, but it can also lead to the presence of aflatoxin M1 in milk, which is a known carcinogen for both humans and animals.
Several countries have established legal limits for aflatoxin M1 in milk intended for human consumption, ranging from 0.05 to 0.5 ppb.
Ergot alkaloids, which belong to the Claviceps purpurea group, are commonly found in fescue grass and are known to have detrimental effects on cattle health. The mode of action of ergots is vasoconstriction, which can lead to lameness in cattle due to gangrenous necrosis in the feet. Additionally, ergot toxicity can cause necrosis of the tail and ears, further affecting the animal’s health.
In addition to the physical symptoms, ergot toxicity has a negative impact on the immune system and lowers milk production. This decrease in milk production can be attributed to the fact that the blood supply to the udder is reduced due to vasoconstriction. Ergot alkaloids also affect the reproductive system, leading to prolonged gestation periods, weak or stillborn calves, and reduced fertility.
