Dry conditions this summer resulted in more silage put up than typical. Most was done well, but there are always a few piles put up under less-than-ideal conditions. While clostridial fermentation can cause issues when harvested too wet, dry silage is more likely to contain mold and yeast growth that can decrease animal performance and, in some cases, cause more extreme concerns.
In a recent UNL BeefWatch article (beef.unl.edu), UNL Beef Systems Specialist, Dr. Mary Drewnoski shared: even before harvest, mold growth and mycotoxins can be an issue. Mold can be found on plants growing in the field, so unfortunately, you can have no live field mold present after fermentation but still have the mycotoxins produced in the field. This is because once produced, most of these toxic compounds are not destroyed by heat, time, or fermentation. Thus, if you see mold at harvest, it may be a good idea to test for mycotoxins. A basic mycotoxin screening will cost around $170.
Storage molds can be a big issue in silage that was put up too dry and this can be amplified if there was poor initial packing. Molds require oxygen from air to grow. Regardless of moisture at packing, uncovered piles are also likely to have increased risk of high mold counts.
The primary feeding concerns related to storage molds are reduced silage nutritional quality, bunk life and palatability. Mold counts (typically $30-40) can help to determine how much storage mold is present and an identification can help to see if you might have the potential for toxins lurking in your silage. Depressed digestibility (reduced energy availability) can occur with mold counts greater than 100,000 colony-forming units (cfu) per gram of DM even without mycotoxins present. At 300,000 cfu/g of DM, caution is advised as this can result in reduced feeding value, reduced intake, reduced performance and digestive issues.
If storage mold is present, the rate we feed out of the pile is critical. Make sure to feed enough that you remove at least 6 inches per day off the face, with 12 inches being more ideal, and do not pull off more than 1 feeding at a time. Mold will start to grow rapidly when exposed to oxygen, significantly reducing the feeding value and increasing the risk of negative effects on the cattle being fed.
Unfortunately, high mycotoxin levels can be found with low mold counts. This is because the amount of mycotoxin produced by mold depends on growing conditions. The safe level of mycotoxin is hard to establish as symptoms are often nonspecific and may be wide-ranging. Depending on the toxin present and concentration, symptoms may range from reduced intake and performance to rumen and liver damage to depressed disease resistance to reduced conception and infertility to late gestation abortions. Contaminated feeds often contain multiple mycotoxins, potentially amplifying the expected effects.
Once again, testing and diluting contaminated silage to acceptable levels in the ration to reduce impact is recommended. If you can, feed to animals that will be lest affected, avoiding those most susceptible like young calves and stressed animals.
Less than perfect silage is still useable but comes with some risks. Yeast and mold growth and mycotoxins can cause issues if risks are ignored, however with a little bit of testing and planning, poor quality silage doesn’t have to be a total loss.
-Ben Beckman is a beef systems Extension Educator serving the counties of Antelope, Cedar, Knox, Madison and Pierce. He is based out of the Cedar County Extension office in Hartington. You can reach him by phone: (402) 254-6821 or email: firstname.lastname@example.org