(Previously published on Feedstuffs on June 24, 2019)
Adverse weather conditions during or after baling can allow mold growth, but pastures may also pose contamination risk.
With the abundance of rain that has fallen in the Midwest over the last several weeks, farmers and ranchers are likely dealing with moldy hay and spoiled feed. Moldy or spoiled feed can present a health risk for multiple species, Oklahoma State University Cooperative Extension equine specialist Kris Hiney said.
“Hay can be unfit for livestock due to excessive moisture while baling or exposure to the elements, such as excessive rain or flooding. Molds present in the feed may contain mycotoxins, which can cause significant health issues,” Hiney said. “While only some molds produce mycotoxins, these are visually unable to be differentiated, and the presence of mycotoxins is difficult to assess.”
Animals that consume contaminated feeds can experience liver and kidney damage, neurologic disorders and estrogenic effects. While mycotoxins may not always cause clinical diseases, they can interact with animal stressors to decrease efficiency and reproduction and increase disease incidence, which producers may not directly attribute to the feedstuff, Oklahoma State said.
Adverse weather conditions during or after baling can allow mold growth, because mold grows and thrives in warm and wet conditions. Hay with 14-15% moisture is subject to mold. Humidity, along with prematurely baling or excessive rain and flooding events, can promote mold growth.
Hiney said it is important for producers of all forage-consuming species, including cattle, sheep, goats and horses, to carefully monitor animal performance when weather conditions have increased the likelihood of spoiled or moldy forage.
“While mycotoxins typically are associated with grains, forage also can contain disease-causing agents,” she said. “Ochratoxin is typically associated with only death in young calves, as it’s rapidly degraded in the rumen in more mature animals. However, this mycotoxin has been associated with cattle deaths and abortions believed to be due to disruption phenylalanine metabolism.”
Aspergillus fumigatus is a mycotoxin found more frequently in hay. Animals that consume hay containing this mycotoxin will exhibit symptoms similar to those of protein deficiencies or malnutrition, including poor haircoat, immunodeficiency and poor performance, Hiney said. Animals already stressed by environmental conditions may experience suppressed immune systems if they consume contaminated hay.
Hiney added that producers must look beyond harvest forages, because pastures also are susceptible to mycotoxins.
“Unfortunately, mycotoxins are not easily verified, as their distribution in feed may be highly variable,” she said. “Samples must be handled carefully prior to analysis. Visual appraisal may not be useful for producers, and the use of black lights is not encouraged as a detection methodology.”
Producers concerned with the presence of mycotoxins or mold spores can send samples to a diagnostic lab.
If the presence of mycotoxins can not be verified, producers should carefully monitor herd health regarding reproductive efficiency, feed utilization and gain and overall health status, Hiney said. Keep in mind that even if mycotoxins are not present, the presence of mold can decrease the digestibility of feeds and result in nutrient loss. For example, Hiney said cattle may experience a reduction of 5% in their ability to extract energy. The overall nutrient composition of the diet may need to be increased to compensate for the energy reduction.
“Horse owners should be more vigilant when feeding moldy hay compared to cattle, sheep and goats. Ruminants may be better protected against mycotoxins due to degradation in the rumen. However, chronic exposure in the ruminant can be deleterious and may depend on other dietary factors,” she said.
Alternative forage sources should be investigated, if possible. If moderately moldy hay must be fed, consider having it tested for nutrient content. Spoilage may be sufficient enough to be detected through traditional forage testing. Hiney said it is important to feed in a very well-ventilated area or steam the hay, if possible.
“This is especially true for horses that typically are fed in more confined areas such as stalls and barns. Mold spores and dust can cause significant respiratory disorders to both the animals and the humans handling the feed,” she said. “More importantly, moldy forage may decrease intake due to its palatability, further reducing performance efficiency. Don’t force animals to consume hay by withholding alternative feedstuffs.”