Dairy producers need to take steps to manage the risk of mycotoxins, which occur routinely in feeds and forages, causing a variety of health issues and reduced milk production, according to Lon Whitlow, professor emeritus at North Carolina State University.

Whitlow said post-harvest factors that promote the occurrence of mycotoxins include damage to feed, such as broken kernels and trash content; lack of proper storage conditions or facilities that expose feed to damaging levels of moisture, heat, air and pH; and improper feeding methods.

Speaking at a seminar sponsored by Prince Agri Products, Inc. at World Dairy Expo in Madison, Wis., Whitlow said because the ensiling process is never perfect, silages can commonly contain unwanted bacteria, yeasts and molds, along with mycotoxins produced by molds. “As a result, excellent silage management is essential to help ensure a high-quality product,” he said. 

Whitlow said that mycotoxin occurrence is influenced by local conditions, including weather, hybrid and varietal resistance to environmental stresses, the timing of planting and harvest, and field rots. Dry weather, he said, typically results in mycotoxins such as aflatoxin and fumonisin, while wet weather can promote zearalenone, T2 and deoxynivalenol (DON), which is usually a marker for the presence of other mycotoxins.

Symptoms in dairy cattle include digestive upsets, low feed efficiency, milk loss, poor fresh cow transition, poor reproduction, nervous disorders, increased disease and higher culling rates. “Mycotoxins are also considered one of the most important dietary factors that suppress dairy cattle’s innate immune system,” he added, leaving them more susceptible to a host of health disorders, reduced milk production and lower milk quality.  

He noted that diagnosis can be difficult, since a mycotoxin cause may not be apparent.  “Mycotoxin exposure may be undiagnosed, but a key reason for herd problems,” he said.

Whitlow offered the following management recommendations to reduce the toxicity of mycotoxins:

  • Improved field and storage management.
  • Feed treatments to reduce mycotoxin content, such as adsorbents that help reduce digestive absorption of toxins. 
  • Better nutrition management, such as immune stimulants and the use of antioxidants to reduce oxidative stress.

Approximately 1.7 percent of consumed aflatoxin in feed is transferred to milk. Milk containing > 0.5 parts per billion aflatoxin cannot be marketed.  

Wendell Knehans is director of specialty products at Prince Agri Products, Inc.