One of the most frustrating nutritional problems on dairy farms today stems from the increasing rate of mycotoxin infections from grains and forages. The mycotoxin problem is becoming so common that the University of Wisconsin has put together a "task force" of extension people, nutritionists, and agronomists to come up with answers about where it is coming from, how to prevent it, and how to better deal with it once it is there.

The presence of mycotoxins is of concern because of the many health problems that can develop when feeding them. Mycotoxins are secondary metabolites (or waste products) of molds. All molds produce these secondary metabolites, although not all are produced in quantities toxic to a dairy cow or heifer. Some molds produce one or two specific types of mycotoxins, while some produce as many as 6 varieties. There are over 350 known mycotoxins with varying chemistries, and in many cases, they are very similar. Each represents a particular analytical challenge to the testing laboratory and can be a devastating problem to the animal ingesting them, along with an economic burden to the producer.

Mycotoxins are invisible, so identification by sight is not possible. However, the molds that produce the mycotoxins may or may not be visible. Unfortunately, this means that the presence or absence of visible mold is not necessarily proof that a mycotoxin infection exists. Even more confusing is trying to identify the scope of mycotoxicity by its symptoms in the animal.

In research, experiments are developed to show the effect of a single purified mycotoxin. Often, high levels of this mycotoxin must be fed before obvious symptoms are evident. On the farm, cows don't eat individual mycotoxins. Rather they ingest a variety of mycotoxins, that, even if the concentration (usually measured in parts per billion) is low of any single one, the combination may present a significant challenge to the cow. The concentrations that cause problems in the lab are sometimes 10-100 times greater than those that create problems in the field. These differences are also the result of the existing levels of stress on the cow (and on the owner). This does help explain why a level of mold or mycotoxin in the field could be below a reported research level determined to cause symptoms, and still cause problems.

The main effect of mycotoxins tends to be on the immune system. Some common and obvious side effects are lower milk yields and reduced digestion of feedstuffs, as evidenced by undigested forage in the manure. Dry matter intake can be either reduced or increased (without concurrent increased milk production). Zearalenone, an estrogenic mycotoxin, causes reproductive problems, irregular cycling, and mammary and udder swelling. Also, acidosis can show up as a secondary problem, along with permanent kidney or liver damage. Another factor in the mycotoxin problem is the fact that molds grow in hot spots, so some feed may be good, while another area near by may be infected. This makes sampling for mycotoxins a challenge. An estimate of the frequency of mycotoxin infections can be seen in the reports from feed testing laboratories performing mycotoxin assays. These labs are reporting that 25 to 40% of all feeds tested have mycotoxins. Of course, the percentage is higher in this group than in the general population of feeds, since the reason they were being tested is that they were under suspicion for mycotoxins in the first place.

There are two main reasons generally cited for the increasing incidence of mycotoxin infection. One is the general lack of moldboard plowing today as compared to 15 or 20 years ago. Molds are a common inhabitant of soil, and moldboard plowing greatly reduces their ability to survive. Fusarium molds enter the plant as the seed germinates. These molds will affect the plant during growth, but serious mycotoxin production will probably not occur until dry down. Another reason for mycotoxin prevalence is the increased use of plants that are bred for high performance and other traits, but may have lost their resistance to molds.

Prevention of molds in forages and grains is always the best strategy. Such practices include:

1. Not putting new forage into mold infested structures
2. Using proper harvesting techniques
3. Removing feed at a rapid pace and using proper face management of bunkers and bags
4. Using inoculants on high moisture forages and grains (Pro- Store) to help insure proper fermentation and a rapid lowering of pH after harvest, making it difficult for molds to grow
5. Cleaning feed bunks daily
6. Harvesting at recommended maturities
7. Practicing proper packing and covering strategies
8. Occasionally moldboard plowing
9. Keeping chopper knives sharp
10. Using forage and grain varieties that are resistant to molds, and ear, foliar, and stalk rot diseases

If we still have infected feed, one commom suggestion is to add sodium bentonite. Sodium bentonite is a name for a class of clay compounds that are different enough from each other in their structure and manufacturing processes that their effectiveness can't be assured. Some popular brand names include Feed Bond, Diabond, and Novasil.

At ANC we may recommend a bentonite product, and also microbials, which seem to help the rumen function better by helping maintain rumen bug populations. Our consultants will help you with the problem. Besides the use of an additive, some of the infected feed may need to be discarded or diluted. Many times, a certain amount of feed can be removed from the surface exposed to air to help "get ahead" of spoiled feed. Usually it is far more economical to do this and reduce the problem rather than continuing to feed suspect forages or grains. Common sense in this case will pay you big dollars! Do not spread bad feed on the field. Instead, compost them and burn them if allowable. A rapid turn-around can be seen in the cows when an effective defensive strategy has been instituted. Long term health benefits will far outweigh the cost of wasted feeds and beneficial additives! Return To Table Of Contents