Any time a growing grain-producing plant is damaged, there is a potential for changes in the plant or grain on the plant contaminated with fungus/molds to grow. The most common change in stressed plants is the accumulation of nitrates.
Aspergillus or Fusarium will be the most likely fungi to be contaminating harvested grain from storm-damaged corn in south central Nebraska.
It is really important to know that most molds are not toxic. Therefore just because mold growth is observed doesn’t mean the feedstuff will harm livestock. Even though a mold may not be toxic it can still cause feed refusal. Not all livestock species are equally sensitive to mold contamination and not all production groups are equally sensitive. For instance pregnant and young animals are more sensitive than mature non-pregnant animals.
Nitrate accumulation in stressed plants can be harmless or cause serious harm depending on:
- the level of nitrate in the feed harvested from stressed plants,
- the life stage of the animal, and
- the species of animal.
Nitrates accumulate in the forage portion of the plant, so nitrates are not a concern in grain harvested from stressed plants. Additionally, it is important to know nitrate levels will always be highest in the bottom part of the plant and lowest in the top foliage. Nitrate testing is simple and reasonably quick. Your local UNL Extension Educator can help you locate the nearest facility that does forage nitrate testing.
Feed containing a nitrate level less than 1000 parts per million (ppm) seldom is associated with an animal health concern. Feed containing a nitrate level greater than 1000 ppm may be a concern in younger animals and levels over 2000 ppm should not be fed to pregnant cattle. Feeder cattle are reasonably resistant to nitrates but feeds containing more than 4000 ppm should not be fed to any animals.
Molds in corn grain of concern could be either Aspergillus or Fusarium. Your UNL Extension Educator can be a great help in identifying mold growing on ears of your storm-damaged corn before the grain is harvested. Both of these fungi are potentially dangerous when found in livestock feed. Toxins produced by molds are extremely stable, therefore if a significant level is found, the level will not decrease over time. Silage produced from damaged plants and grain harvested from mold-infested plants is potentially a problem.
Good silage management is critical to reducing the risk of continued mold growth after ensiling. Proper packing to remove oxygen and improve fermentation is critical to ensuring that the pH stays below 4.5.