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Feeding the 2019 crop: Quality issues to consider

Jason Ertl
University of Minnesota Extension
Swine can be especially susceptible to the effects of particular mycotoxins in feed.

It’s no secret that crop producers in the upper Midwest faced numerous climatic challenges this past year. Snowstorms well into April led to a wet spring and delayed planting, and as we inched closer to harvest season, the question on everyone’s mind was whether or not the crop had reached physiological maturity.

This concern became especially evident in the region’s corn crop, as late planted and those perpetually wet fields resulted in some higher harvest moistures and lighter test weights. When other harvest complications are added into the mix, such as LP shortages or weather-related delays, the risks related to grain quality and contamination become of greater importance.

Since nearly 60-70 percent of the US crop is destined for feed, the implications of decreased feed quality could influence a large number of livestock producers. Unfortunately, the hog industry is not immune to these issues, and pork producers will need to remember this as the 2019 crop makes its way to various rations. Being aware of the different quality issues that could occur because of growing or storage conditions and knowing how to properly test feed is important in order to achieve optimal performance in the barn.

Mycotoxins in the grain supply

One major concern related to feed quality is the presence of mycotoxins. Mycotoxins, which are toxic compounds produced molds, can be found in various different grain crops and like other molds common in everyday life, are influenced by things like temperature, humidity and moisture.

Weather conditions this past summer in some parts of our region led to favorable conditions for mycotoxin development, but it is also important to remember that they can originate throughout a plant’s life cycle as well as during harvesting, storage, or processing.

Swine can be especially susceptible to the effects of particular mycotoxin compounds, and depending on their phase of the production cycle, significant impacts on health and productivity could be observed. While hundreds of specific mycotoxin compounds have been identified, a handful of those are of particular interest and of concern to hog producers.

Even small amounts can pack a punch

Like other contaminants, mycotoxins are typically measured in parts per million (ppm) or parts per billion (ppb). To put that into perspective, one part per million would be the equivalent of one corn plant in about a 40 acre corn field. One part per billion, on the other hand, would be the equivalent to one corn plant in about 40,000 acres of corn. Because they can’t be detected by smell or by the naked eye, the importance of regular feed analysis cannot be understated.

Fusarium Toxins

The Fusarium group of mycotoxins, such as vomitoxin, zearalenone and fumonisins, are the result of cool, wet growing conditions, and pose the greatest threat to swine compared to other livestock.

Vomitoxin

Deoxynivalenol, or referred to as vomitoxin, DON or “refusal factor”, is most commonly found in the upper midwest in corn but can also be found in small grains. Symptoms of vomitoxin include reduced feed intake at levels of 1 ppm. Increased concentrations (5-10 ppm) can result in feed refusal and ultimately weight loss and vomiting.

Zearalenone

The mycotoxin zearalenone, or the “giberella toxin”, often occurs as a result of improper moisture and or storage conditions. Zearalenone is typically found in cereals as well as corn, and results in estrogenic effects such as vulva reddening or swelling, rectal or vaginal prolapse, irregular estrus cycles and reduced litter size, with pre-pubertal gilts being the phase of production most susceptible. Young growing pigs can be affected in concentrations of less than one part per million, while breeding females, finishing pigs and boars can be affected at 2 ppm and 3 ppm respectively.

Fumonisins

Fumonisins can be found throughout the corn producing states, especially when cool, wet weather at maturity follows drought stress. This mycotoxin mainly affects the heart, liver and lungs with acute symptoms such as immunosuppression and pulmonary edema (fluid in the lungs). In the situation where low amounts of fumonsin are ingested over long periods of time, lower feed intakes and lower growth rates are observed.

Weather conditions also bring out-of-town mycotoxins

Aflatoxin

Aflatoxin (Apergillus flavus) is most commonly found in the southeast US, but can occur in the corn belt during drought conditions or grain stored at high moisture and temperature. Aflatoxin, a known carcinogen, is also the only mycotoxin regulated by the USDA as there are safety implications in grains intended for human consumption. Low amounts such as 20-200 ppb can result in decreased growth performance, and consumption at levels over 1000 ppb can result in death. Aflatoxin accumulates in body tissues over time, resulting in chronic toxicity being more commonly observed than acute cases. Reduced liver function and suppressed immune system (resulting in secondary health issues) are among the most common symptoms.

Ochratoxin

Like aflatoxin, ochratoxin is most commonly found in the southeastern states, but has been documented in the midwest. Ochratoxin is also a known carcinogen and a concern for human health. When consumed at 1-3 ppm, it can cause liver or kidney damage, reduced feed efficiency and increased mortality.

Further details of mycotoxin activity in swine diets can be found in this Kansas State University publication: https://z.umn.edu/KStateMycotoxins

Testing feed for added insurance

In the event of favorable conditions for fungal development and potential for mycotoxins, swine producers, nutrition specialists and feed mills may be curious about the quality of grain used in their rations. Regularly testing not only grain, but also complete feed, should be a standard operating procedure to ensure correct nutrient content and feed consistency. In situations where feed or grain contamination is likely, many grain or feed testing facilities have the ability to test for mycotoxins.

Sampling methods for success

The key to collecting reliable and accurate lab results begins with closely following sampling and submission procedure. Since every feed mill and hog farm is different, it is difficult to generalize sampling methods, but there are some concepts and considerations to keep on your mind throughout the sampling process.

Getting a representative sample

Depending on the sampling equipment used (slotted grain probe, for example) it is essential to get multiple, and random samples from the grain/feed source (bulk container/feed bag/feeder). Combine and mix these samples to create a composite sample. Splitting into subsamples can allow for more manageable shipping and processing, as well as provide a secondary sample to save as a backup in the event that retesting becomes necessary.

Paper or plastic?

Feed and grain is often submitted in clear plastic zip-top bags, however, paper or breathable cloth bags are favored by some labs due to their ability to prevent excess condensation or moisture in potentially contaminated feeds. As always, properly labeling samples is crucial. Information such as sample date, feed/grain type, lot and sampler initials are the minimum amount of detail needed. Producers with questions about grain/feed sampling should contact the local Extension office, nutritionist, veterinarian or testing lab for further instructions and recommendations.

What to do with contaminated feed

Since it’s impossible to remove harmful mycotoxins, producers will need to explore other options or uses for contaminated feed or grain.

  • Feed potentially contaminated feed to small test groups of pigs and closely monitor for symptoms of mycotoxin toxicity. If Fusarium toxins are suspected (Zearalenone or Vomitoxin, in particular), use a test group of prepubertal gilts and observe if symptoms like swollen vulvas or reduced feed intake occur.
  • Once mycotoxin levels are established following laboratory analysis, mycotoxin contaminated feed can be blended with higher quality grains to create a final product below utilization limits.
  • Depending on the specific mycotoxin and/or level of contamination, marketing grain to other livestock producers may be a solution. Ruminants such as beef cattle or sheep are less susceptible to the effects of mycotoxin toxicity.

Ertl is the UM Extension Educator for Ag Production Systems in Nicollet and Sibley Counties, Minn.