Using corn as a major component of your cattle feed?No problem, except for the increasing price.Use it until the silo is empty.Using more distillers grains to help manage feed costs?Better be able to accurately predict consumption because shelf life is the trade off you’re making.
To be more accurate, distillers wet grains are the product to watch closely, according to Dr. Kurt Rosentrater, Lead Scientist, Agriculture and Bioscience engineer at the USDA Ag Research Service in Brookings, SD.His research indicates a 5 to 7 day self life, in general, depending on ambient storage temperatures and humidity levels.You can bet long today but when the typical Midwest summer weather hits in late July and early August with what always seems like triple digit temps and humidity, keep a close eye on what might be rapidly growing on your rations.
“Distillers dried grains with solubles (DDGS) is generally dry enough – it’s shipped with 10% moisture or less – that shelf life isn’t a problem,” he said, “But distillers wet grains will spoil.It’s the high water content – over 50% - that makes it susceptible to rapid spoilage.”
Rosentrater pointed out another problem: shrink.DWG stored in ambient conditions can quickly lose moisture, meaning it’s even more important to keep tabs on usage.
The problem, he said, starts when DWG at the plant level are conveyed away from the ethanol processing area.“DWG at that point are piping hot, about 180 degrees, making them pretty much sterile.They’re dumped onto uncovered holding bunkers where they can pick up any bacteria, yeasts or mold spores that naturally happen to be in the area.”
Next, the product is scooped onto trucks using front-end loaders, two more points of possible contamination, before they’re delivered to the feed lot.Sometimes storage at the feed lot can be in less than sanitary conditions, which can also contribute to a shortened shelf life.
Because DWG have such a high moisture content, long distance transportation is fairly uncommon.With the high cost of fuel, it generally doesn’t make economic sense to ship the product more than an hour or so away from the plant, because you’re shipping so much water.
“You can see product degradation. It’s a visual thing. Yeasts and molds grow on the surface and there are color changes,” he said.“Unfortunately, I haven’t seen much research on when it no longer pays to feed DWG.Most feed yards will use it until cattle refuse to eat it, or when it’s too moldy.”
Some research on extending shelf life by using airtight silo bags shows a significant increase in allowable shelf life, maybe adding several weeks or months, depending on ambient temperature.Storing in bunker silos with a plastic cover is also a promising method.Keeping the product covered in an air tight as possible environment will inhibit further on-site contamination and greatly reduce the growth of unwanted organisms.
“Currently, there are no standards,” he said.“Do you stop feeding when you find ‘X’ level of microbes?‘X’ amount of shrink?At what point does it matter?Those are very serious questions that still have to be answered.”
Rosentrater’s research has turned up a variety of bugs in DWG including several lactic acid-producing bacteria, yeasts, molds and fungi.“One thing to worry about might be aflatoxin, but so far we haven’t found that yet, although we did find some fusarium in a few samples.”
His suggestions:Buy enough distillers wet grains to last 3-4 days; be careful about how you store it; and possibly consider using growth inhibitors – there are several available in the marketplace.