In the Upper Midwest this fall, a variety of factors resulted in the harvest of a drier-than-usual corn silage. An atypical hot, dry spell around Labor Day started to dry out the corn plants; however, most producers were using this period of good weather to harvest alfalfa. Next, we received an early frost.

Typically, I see a range in corn silage dry matter content from approximately 30 percent to 40 percent. However, this year, the range has been between 35 percent and 50 percent dry matter. Nutritionally, this results in more heat damage and reduces energy and protein availability in the fermented feed. Silage with more than 40 percent dry matter is more conducive to the growth of potentially-toxic microbiological agents, making nutritional and disease problems more likely. Specifically, be on the lookout for:

  • Listeriosis. The aerobic bacteria Listeria monocytogenes, found in soil, manure, and the digestive tract, grows best in dry silage with poor compaction. Feeding silage contaminated with this bug can infect the animal through any sore or abrasion in the mouth. The listeria bacteria can then migrate to the brain, resulting in partial paralysis of one of the cranial nerves, and often causing an ear or eyelid droop or tongue paralysis. These early symptoms progress to more general symptoms of central nervous system infection, including an inability to swallow, head pressing, and circling in one direction. Thus, it is often called “circling

    The migration of the bacteria takes time, so symptoms usually appear two to three weeks after feeding the contaminated silage. High doses of penicillin can treat listeriosis in the early stages; however, in advanced stages, treatment is usually ineffective.

    And, the process of feeding will introduce more oxygen into loosely-packed silage, so dry silage can incubate listeria all year, not just when first harvested. This makes proper feedout critical.

  • Molds and mycotoxin. Molds need oxygen to grow. With a drier-than-desired silage, packing can become difficult, resulting in more oxygen retained between the silage particles and, potentially, more mold growth. While mold organisms die off as the silage is preserved, their spores remain — ready to germinate and multiply again in favorable conditions, such as when air is introduced at the face at feedout.

    Many of the molds produce mycotoxin. Among other things, mycotoxin can inhibit the immune system. This, in turn, can make cattle more susceptible to a wide array of health problems, including mastitis, reproductive disorders and foot rot.

    If mycotoxin-contaminated feed is the only feed available, several strategies can be used to minimize the risks, including:
    • Use a smaller portion of affected feed.
    • Feed an additive designed to counteract the mycotoxins. Adsorbents, such as bentonite or aluminum silicates that bind to the mycotoxins and prevent absorption, have had some success. In my experience, these products have worked better for aflatoxin than for the fusarium toxins.
    • Direct-fed microbials have been developed that either alter the mycotoxin structure and render it non-toxic, or actually destroy it.

    If you put up unsually dry silage this fall, be on the lookout for potential health-related problems.

    Brian Gerloff is a veterinarian and operates Seneca Bovine Service in Marengo, Ill.