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What Caused The Molds and Mycotoxins In My Forages?

Article by Larry Roth, Ph.D., PAS – Cargill Animal Nutrition

 

Imagine the scene: Your nutritionist walks into your office, sits down across the desk from you, and hands you assays of your forages that indicate you have high levels of molds and mycotoxins. “Where did these evil organisms come from?”, you ask. It is helpful to be aware of the many factors at play when forages are affected by molds and mycotoxins.

A mycotoxin is a secondary metabolite produced by mold. One mold species may produce many different mycotoxins, and several mold species may produce the same mycotoxin. High mold levels do not necessarily mean mycotoxin levels will be high. Different micro-environmental conditions can trigger production of varying levels of various mycotoxins by a given mold species. The exact environmental triggers for particular mycotoxins and levels are not precisely clear, but understanding and managing the factors contributing to mold growth can lessen mycotoxin presence in forages.

There are favorable and optimum temperature ranges for growth of the Aspergillus, Penicillium, and Fusarium molds (Figure 1). Certain Aspergillus and Penicillium molds prefer warm, Summer conditions, while Fusarium generally thrive in cooler temperatures, as in the Fall, for optimal growth. Aspergillus molds are the primary aflatoxin producers; aflatoxin is most commonly observed in heat and drought conditions. Although a few Penicillium molds produce aflatoxin, most members of this genus produce mycotoxins of lesser importance. The Fusarium genus is perhaps of greatest concern in the Upper Midwest due to the production of vomitoxin (DON), zearalenone, and fumonisin mycotoxins. Fusarium species like the cool, wet conditions which have come to typify Fall in the Midwest.

Figure 1. Favorable and Optimum Temperature Ranges For Aspergillus, Penicillium, and Fusarium molds

While forage producers cannot control temperature, rainfall, and humidity, they can influence other factors involved in mold growth and the potential for mycotoxin production.

Soil Health: A healthy and diverse microbial population in the soil will enhance crop residue degradation, which could otherwise serve as a mold reservoir. A young corn plant pushing its first green leaf through last year’s crop residue could become infected with harmful molds. Healthy soil will also have greater water-holding capacity to sustain growing plants during dry spells and allow water to readily drain during excessive rainfall. Proper tillage can maintain some surface residue to reduce soil erosion, while excessive tillage may reduce soil aggregation, lowering nutrient and water-holding capabilities.

Agronomic Practices: Any stressors on the plant can tip plant health in favor of mold production. Proper planting time, plant population, plant genetics, insect control, and fungicide use are among the many agronomic practices that influence plant health and can bolster the plant in its battle against harmful molds.

Harvest Conditions: Timing harvest before the appearance of cool, wet conditions favorable for Fusarium growth may reduce molds and mycotoxins brought from the field to the silage storage structure. Chopping at a proper moisture, reducing chop length as the crop dries, and proper packing can reduce mold growth during ensiling. Segregating mold-infected crops from clean forages during ensiling may pose logistical challenges, but could pay-off in animal health and production by keeping clean forages clean and enabling feeding strategies based on animal susceptibility to mycotoxins.

Storage and Feed-Out Conditions: Proper packing to exclude oxygen is essential in controlling the growth of aerobic molds, such as Fusarium and most Aspergillus. Recent research suggests P. roqueforti may continue growing in well-packed silage, however. Mold spores can survive ensiling, and then start growing with the reintroduction of oxygen and proper temperature at feed-out. Proper feed-out practices are always essential when managing ensiled feeds, and even more critical with forages infected with mold at harvest.

High mold levels do not necessarily mean high mycotoxin concentrations in forage. On the other hand, mycotoxin concentrations could be high in forage with low mold counts due to toxin production pre-ensiling. Viewing a forage assay with high mold counts or high mycotoxin levels is never a pleasant experience for a forage producer. Taking the time to review the production practices that resulted in the particular forage can help change the course for future forage crops, however.

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5 Tips for Success this Corn Silage Season

  1. Anticipate Moisture Changes
    Begin harvest at a plant moisture of 70% and ¾ kernel milk line.  Starting a little early is better than starting a little late.  Harvests almost never “go perfect” so anticipate a day or two of down time and don’t let the down time get your corn silage “too dry”.  The goal should be to have the year’s worth of corn silage in the 64% to 67% average.
  1. Use Shaker Boxes
    Talk with your nutritionist and do some shaker boxes on total tmr length and individual forage lengths.  From this, determine how long you want to chop your corn silage.  This value can range from 18 mm up to 30 mm.
  1. Monitor Loads
    Monitor loads as they come in for kernel processing.  In a cup full of silage, there should be no whole kernels and many of the corn pieces should be 1/8 to ¼.
  1. Pack for High Densities
    On large bunkers and piles, make use of a second packing tractor.  Many dairy operations today can chop large feed volumes very fast and this increased volume requires extra weight on the pile to keep packing densities high.
  1. Reduce Shrink
    Preserve your yields and work by using extra plastic layers, oxygen limiting barriers, innoculants, lining bunker walls with plastic, making tires touch and lining edges with dirt to hold down plastic.  These steps can decrease shrink by 5 to 10%.

Content courtesy of Joe Gier, Landmark Dairy Nutritionist

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Grain – A Major Contributor to Feed Quality

At Landmark, we make sure the customers are getting the best corn grain around. Landmark’s Grain Division helps do this by taking the quality of all ingredients that are used in manufacturing feed in our mills very seriously.  All ingredients must meet certain specifications and quality measures before they can be received into our manufacturing facilities.  This includes all of the locally grown corn that is used in the production process.

The USDA has a standard grading scale for all corn that includes test weight, damaged kernels, broken corn and foreign material.   We test every load of corn that goes into our mills for these traits as well as check for any other visual issues with the corn.  We utilize #2 Yellow Corn or better in our mills.  We also make sure that the moisture content of the corn is suitable for the use so that the feed flows well and has a lengthy shelf life.  We also check for any odors that might be present to be sure the grain has a sweet fresh smell.

We store grain at our facilities in anticipation for it being used in the mill as well as receive directly from the farm.  Some of the storage bins are directly connected to the mill and all the grain is tested before being put in the bin.

We also test for toxins that may be present in the corn to make sure they are below the approved thresholds for corn. Usually in Wisconsin we are in good shape as our climate and growing conditions generally limit the development of toxins in corn.  Unfortunately, it can show up occasionally, so we have official testing equipment and trained staff that look and test for these regularly.   We want to be 100% certain that all the grain is of great quality and is manufactured under the best practices to provide maximum performance for your animals.

Article By: Emily Sendelbach, Animal Nutrition Customer Solutions Specialist

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