Molds and mycotoxins may damage this year's corn crop

This is a guest blog by Mike Hutjens, Extension dairy specialist with the University of Illinois, Urbana.

Dairy managers and corn growers share the same concern: a wet and late spring delayed planting, a lack of heat (degree days) slowed growth, and a record wet October with cold weather has a huge corn crop at risk with mold development. Moldy corn reduces bushel weight, corn quality, nutrient content, and increases the risk of mycotoxin formation. Mycotoxins are toxic substances produced by fungi (molds) growing on grain or feed in the field or in storage. Mycotoxins associated with cool and wet conditions are deoxynivalenol (also called DON or vomitoxin), zearalenone, T-2 toxin, and fumonisin. Aflatoxin is another toxen, but it is associated with hot weather and/or drought stress conditions.

Signs of mycotoxin in dairy cattle include immune suppression (cattle do not respond to disease challenges), rumen disorders and reduced microbial digestion, loose fecal discharges, reduced dry matter intake, decline in fertility, and hormonal-like changes (udder development and fertility).

Mycotoxin risk levels for dairy cattle are listed below (expressed on a total ration dry matter basis). Dilution with clean feed can reduce mycotoxins, but contaminated feed can vary greatly in concentration (note some toxins are listed as parts per billion; others are parts per million):

DON (vomitoxin) < 5 to 6 parts per million
Fumonisin < 25 ppm million
T-2 toxin < 100 to 200 parts per billion
Zearfalenone < 300 parts per billion
Aflatoxin < 20 parts per billion

If you are concerned that mold risks could be a problem, the following guidelines may be helpful:

1. Testing for mycotoxins can provide an estimation of risk. Tests can be expensive and sampling and feed variation can reduce the usefulness of the results.

2. Adding a mycotoxin binder can reduce the impact of toxins be reducing their impact in the digestive tract and/or not absorbed (binders include yeast cell wall extracts or MOS products and clay binders).

3. Drying wet corn below 15 percent moisture stops further toxin development.

4. High-moisture corn could increase the risk of additional mold grow until the pH of the fermented corn drops.

5. Adding a grain inoculant to speed up fermentation and stabilize the wet corn is recommended.

6. Young animals and pregnant cattle are at higher risk, while steers can tolerate higher levels.

7. Removing fines, damaged seeds, and cracked corn kernels can reduce toxin risk.

8. If you purchase corn screenings, higher levels of mycotoxin risk can be present.

9. Distillers grains produced from ethanol production can concentrate the level of toxins in the original corn used; know your sources of distillers grains.

10. Corn silage made late in the season with mold damage could have toxins, but the low pH will stop additional toxin production.

11. Adding propionic acid at the time of ensiling can reduce mold development in wet corn.

Grab a 32-ounce cup and check your kernel processing

Last week, we learned of a new use for a 32-ounce cup: checking your corn kernel processing. You know, one of those extra-large plastic cups you get from your local convenience store when purchasing a slushy or soda? We were in Johnston, Iowa, last week for the Pioneer Media Forage Day. During the mock “Forage University,” Pioneer’s Nutritional Sciences manager Bill Mahanna discussed the importance of corn kernel processing as it relates to feed efficiency.

Today’s top-producing dairy cows are no longer peaking at 90 pounds of milk per day; they are making much more milk. This larger volume of milk means that feed is passing through the rumen at much faster rates. This increased rate of passage makes feed processing more important to facilitate faster microbial access. To check your kernels, grab a 32-ounce beverage cup and fill it with corn silage. Next, dump the sample of corn silage onto a table and sort out the corn kernels. If you find 2, 3, or more whole or half kernels, kernel damage (processing) is not optimal.

The USDA says that over 70 percent of kernels damaged is optimal. While this might not be completely feasible, Mahanna recommends producers target the mid to high 60s. To achieve this, you’ll need to set the roller mill gap on your corn chopper anywhere between 1 to 3 mm. If corn silage is already harvested, it is possible to get your corn silage reprocessed, but it will take a considerable amount of time and money. So, be sure to keep these targets in mind for next year, and track the difference it can make.

Corn crop has people on edge

There was corn being chopped for silage over the Labor Day weekend in southeastern Wisconsin. But chopping still is a ways off for the 191 acres of corn at the Hoard’s Dairyman Farm and for a good many others across the northern tier of states.

Late planting and a record cool summer in many parts of the country have put the corn crop well behind schedule. The last USDA crop progress report put corn at 50 percent dented, compared to a 75 percent average the previous five years.

Still, “don’t jump the gun" after the first frosty night is the warning from Ev Thomas, the (semi-) retired “crops dude” at the Miner Institute in northern New York. Immature corn still has quite a bit of sugar which acts sort of like antifreeze for the plant. Even if leaves get singed by frost (they’re only 10 percent of the dry matter), as long as the stalk is green, the plant continues to mature, says Thomas.

The only way to know for sure if corn is ready for chopping is to chop some and do a moisture test. Chopping at 32 to 35 percent dry matter (34 is ideal) is the goal for bunkers and bags, says Jim Barmore of Five-Star Consulting in Wisconsin. He recommends 5/8- to 3/4-inch TLC (theoretical length of cut) for processed (non-BMR) varieties. His guide: All kernels should be either smashed, rolled, or cracked with no cob pieces larger than a thumbnail after processing. Make sure at least 98 percent of kernels are processed.

Less mature corn silage may be higher in protein but always is lower in starch and energy, says Thomas. Again, a forage analysis is a must.