Spoiled silage is one of the largest concerns of producers today. Not only is the material visually unappealing and potentially not palatable to the animal, it is possible that the growth of spoilage organisms may have led to the production of potentially dangerous levels of mycotoxins. The growth of spoilage organisms reduces dry matter to feed and can greatly compromise the nutritional quality of the remaining material.

Molds and spoilage occurs over a wide range of temperatures, even down to freezing. The biggest cause for spoilage is the presence of oxygen. This is caused mainly by ensiling at improper moisture levels and inadequate packing. Also included is air exposure at feedout due to removing an inadequate volume of material on a daily basis and poor management of exposed surfaces.

Moldy silage generally results from a series of bacterial and fungal interactions. Corn and cereal silages are generally more prone to mold growth than grass or legume crops. Yeast counts in excess of 100,000 CFU per gram of silage are considered high. As a general rule, heavy loads of yeast do not by themselves cause decreased dry matter intakes, however, subsequent mold growth due to elevated pH can affect feed consumption.

Molds produce spores that survive fermentation. Many produce spores before ensiling due to slow harvest or crop damage, which can result in severe aerobic stability problems when the silo is opened and the crop re-exposed to air. Thus, proper management of the crop prior to harvest and following proper ensiling techniques, including the use of an inoculant such as Pro-Store, can greatly reduce the potential problems associated with moldy silage during feedout.

The majority of mold growth (and mycotoxin production) occurs in the field and only secondary growth occurs during storage and feedout. Organisms which grow predominantly in the field generally exhibit minimal activity in storage or during feedout. While both Aspergillus and Penicillium species can be problematic in the storage phase, Fusarium toxin production occurs in the field before practical management steps to limit damage can be implemented.

Aspergillus flavus produces aflatoxin more commonly during drought conditions. Aflatoxin is a known carcinogen, thus is governed in interstate shipments by FDA regulations with allowable levels of 20 ppb in corn and 0.5 ppb in milk. Due to microbial fermentation in rumen, ruminants are better equipped to degrade aflatoxin in rations than are monogastrics. However, transmission of aflatoxin residues in milk is a food safety issue.

Other mycotoxins include those produced by Fusarium graminearum such as vomitoxin, zearalenone, and T-2. Vomitoxin in dairy cattle is considered a “marker” for closely related fungal metabolites that may cause immunosuppression, loss of appetite, diarrhea and reduced milk production. Cattle studies involving zearalonone have shown that vulvular swelling may occur at levels as low as 200 ppb while higher levels can cause reproductive inefficiency and abortions. Studies involving T-2 for dairy animals are limited, but the toxin is very severe and can cause gastrointestinal hemorrhage, necrosis, and diarrhea and has been associated with problems to liver, lungs, and heart.

The use of adsorbents to “bind” mycotoxins found in feeds is a common practice in dairy herds. The traditional methods include the use of clays such as calcium and sodium bentonite, or anti-caking compounds such as hydrated sodium aluminosilicates. Research indicates that aluminosilicates bind aflatoxins, but not vomitoxin. Some research has been conducted using yeast as an adsorbent.

Practical ways to minimize the effects of toxins are to remove material that is obviously spoiled or moldy, and dilute remaining affected feedstuffs with clean feed. Keeping a fork handy by your bag or bunker to remove spoiled feed is probably worth a $100/per minute used! It is not an option to feed the contaminated feedstuffs to transition cows, early lactation cows or pregnant heifers!

Sampling of the suspected silage should be done with care. Obtaining a representative sample is critical when trying to assess mycotoxin levels in feed. Mycotoxin levels detected from a random grab sample out of a silo or grain bin do not precisely indicate the mycotoxin level that exists in selected areas in the storage structure. Generally a one pound sample of the suspected feedstuffs should be submitted to the laboratory. Samples gathered for microbiological analysis should not be frozen – although samples for nutritional analysis can be. The sample should be placed immediately on ice in a cooler and shipped overnight to the lab. Ship the sample early in the week – not over a weekend!

In summary, most problem silages are put into storage too dry. This leads to air penetration with the subsequent growth of spoilage organisms. Silages put up too wet will often undergo a clostridial fermentation (in the case of legumes, cereals and grasses). We need to make sure feed is packed well in all storage methods. Besides packing, it needs to be covered in bunkers and piles. We can also reduce molds in the field by composting moldy silage rather than spreading it. The lack of mold board plowing along with minimum tillage creates more mold problems in the field which can spread to new crops. This year, much of ANC's area of operations experienced drought conditions. This tends to lead to increases in nitrate uptake by plants. Even though the feed is not spoiled as such, it can be deadly for livestock and humans. Increased months of fermentation may reduce levels. Test for nitrates in all new forages as a precaution.

Be aware that the long, as well as short term health of our dairy animals is impaired when we feed spoiled feeds. The cost of lower production is only a fraction of the economic loss. There is no substitute for good forage and livestock management and there is no miracle product that will solve all of our problems. The magic is in the management! Please feel free to call me if you have any questions related to forage

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