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Posts Tagged ‘dairy cows’

postheadericon Mycotoxins are a triple threat to dairy cows

I have always said that Diatomaceous Earth (DE) is good for everyone and everything.  This article talks about cattle benefiting from having DE added to their food supply.

Mycotoxins are a triple threat to dairy cows
By Peggy Coffeen, Agri-View

Mycotoxin challenges in the dairy industry are increasing. This is probably because of uncontrollable weather patterns that are beyond control, as well as the complex nature of dairy rations with multiple co-contaminants, which can cause increased severity of response. 

Lower milk production, reproduction problems and a depressed immune system… sounds like a recipe for disaster. While an array of factors can contribute to these dairy cow dilemmas, the common denominator here could be mycotoxins.

According to Dr. Trevor Smith, Ph.D., University of Guelph, Ontario, Canada, these nasty compounds are showing up more frequently than in the past. Their various varieties and forms can be difficult to detect, but their toll can be devastating to a dairy cow.

“It’s clear that the mycotoxin challenges in the dairy industry are increasing,” states Smith. “This is probably because of uncontrollable weather patterns that are beyond our control, and also the complex nature of dairy rations with multiple co-contaminants, which can cause increased severity of response.”

It is often weather extremes that cause mycotoxins to manifest. Periods of excess moisture promote mold growth, while drought-related stress can be a contributing factor as well. “This last year, in 2012, we had a great example of that right here in the Corn Belt,” he said.

The most concerning mycotoxins for dairy producers are aflatoxin and Fusariums. Testing methods have been well-established for determining the presence of aflatoxins, as these compounds present a human health threat when found above regulated limits in milk. Surveys of the 2012 U.S. corn crop to date have indicated some frequency of aflatoxin, but largely within legal limits.

According to Smith, Fusarium mycotoxins are more complex with a larger number of compounds that vary widely in structure. This makes them difficult to detect in feedstuffs. Analyzing for a marker compound like deoxynivalenol (DON, also referred to as vomitoxin) serves as an indication that Fusariums are present, but the challenge here is that DON may occur in more than one chemical form. For example, in a modified form, it may bond with a glucose molecule that testing does not indicate. “Testing methods will not indicate the conjugated form of DON,” he points out, “so it’s toxic and undetectable.” Other glucose conjugates reported in recent years include zearalenone, fumonisin, nivalenol and fusarenon-X, as well as the very toxic T-2 and HT-2 toxins.


In addition to DON, there are more than 100 other structurally related toxins in the trichothecenes family of Fusarium mycotoxin. These toxins cause overall suppressed immunity and feed refusal, as well as hemorrhaging of the intestinal tract, ulcers, bloody scours and nutrient malabsorption. When zearalenone is present, it can bind estrogen and ultimately lead to reproductive issues, including abortions and infertility.

Significant amounts of fumonisin have been reported this year, which Smith says is “unusual.” The strain of Fusarium fungi that is a major producer of fumonisin is also a major producer of fusaric acid, but feeds are not commonly analyzed for fusaric acid. He points out that while it “takes a lot” of the compound to kill an animal, “it does not take a lot to affect it.” Even when consumed at low rates, fusaric acid can cause a drop in blood pressure that leads to edema and swelling of the udder and feet. When paired with DON, the two “synergistically” reduce feed consumption and cause loss of muscle coordination and lethargy.

Silages are the major source of mycotoxins in dairy feeds. Various toxins may thrive in aerobic conditions that result from poor initial compaction and improper feed-out. Some by-product feeds may also be of concern, like soybean meal. The potential for problems is dependent upon the amount of hulls intermixed with the feed because mycotoxin levels are highest in the hull.


The best way to reduce the negative impacts of mycotoxins is to avoid feeding contaminated silages and other feedstuffs. However, recognizing that may not be a feasible option, Smith suggests feeding mycotoxin absorbents. These are non-nutritive feed additives that pass through the cow’s digestive tract much like non-digestible fibers. They have the ability to attract and bind small molecules like mycotoxins and exit the body through manure excretion. Inclusion rate is key in the effectiveness of absorbents. If fed in excess, the highly branched polymers can also attract and excrete nutrients the cow needs, like amino acids, vitamins and minerals.

Absorbents are available in organic and inorganic forms. Inorganic adsorbents are either natural or synthetic silica-based polymers. Natural inorganic adsorbents (clays) would include zeolites, diatomaceous earth and bentonite. The synthetic inorganic adsorbents include HCAs, which are designed specifically to be effective against aflatoxins.

Organic adsorbents are carbon-based polymers and may offer the most practical use as a feed-grade fiber source with non-digestible properties. They include activated charcoal, lignin and the glucomannan polymer extracted from the cell wall of yeast. The advantage of the yeast cell wall polymer is a high surface area, which allows practical levels of inclusion (0.5-2.0 kg/ton). This minimizes the potential for adsorption of nutrients and essential intestinal metabolites.

Smith shares the findings of a study that looked at the effects of feeding dairy cows a ration containing naturally contaminated hay, silage, corn and wheat with 3.6 ppm DON (on a dry matter basis). The 18 mid-lactation Holstein dairy cows were fed this ration for 56 days and monitored for several metrics including immunologic response.

“When contaminated feed was fed, there was a significant reduction in the ability of immune cells to destroy pathogens,” he notes. However, the inclusion of an organic absorbent (modified yeast cell wall extract) in contaminated feed given to a sub-group improved white blood cell response and showed higher immunoglobulin (IgA) levels.

A significant elevation in blood urea was also observed when the contaminated TMR was fed, which Smith attributes to the DON reducing protein synthesis in the liver so amino acids that are generally absorbed in the digestive tract were oxidized for energy purposes. Urea levels were lower in cows that received the absorbent.

A separate study that looked at the effects of contaminated feed on calves yielded a similar affect. Veal calves fed corn high in DON showed reduced dry matter intake and a significant urea elevation. At slaughter, these calves had lower hot carcass weights, less backfat and smaller loin muscle area than their counterparts fed a diet that was not tainted by high levels of mycotoxins. Another group that was fed higher levels of DON with an organic absorbent, the modified yeast cell wall extract, showed more similar results at slaughter to the control group.

This information was presented by Dr. Trevor Smith during the Leading Dairy Produces Conference hosted by Land O’Lakes Purina Feed earlier this month.
This article was from

Mycotoxins are a triple threat to dairy cows – Ag Weekly