Watch for mold and mycotoxins in dairy cattle feed

By Heather Thorstensen
hthorstensen@agrinews.com

Date Modified: 04/15/2010 8:07 AM

E-mail article | Print version

BUFFALO, Minn. — University of Minnesota dairy cattle nutritionist Noah Litherland spoke to members of the dairy industry March 23 about this year's increased risk of mold, yeast and mycotoxins in feed.

Twenty-five people, mostly dairy nutritionists, attended the first webinar hosted by Minnesota Milk Producers Association.

Mold and yeast are widespread problems this year, from Ohio to Montana, thanks to last fall's late harvest that didn't give enough time for corn to be adequately dried before winter storage. The risks could increase this spring as temperatures rise.

Yeast can reduce feed palatability, resulting in cattle eating less. It can also disrupt digestion, reducing milk production and milk components. Some molds can create mycotoxins which, in addition to the problems caused by yeast, can hinder cattle's reproduction efficiency and immune systems.Mycotoxins were first reported in November but so far do not appear to be widespread.

The good news is a lot of excellent grain exists this year, said Litherland.

"I don't think the story is as bad as it could have been," he said.

Testing recommendation

For peace of mind, he suggests monthly, or even bi-weekly, tests for mold and yeast count in all dairy feed. If results are high, producers may want to spend more money to determine if mycotoxins are there.

"Just because an ear of corn has mold doesn't necessarily mean mycotoxins are present," he said,

For grain sampling, he advised collecting from at least 10 sites. Mix them on a tarp to get a representative sample, then remove opposite quarters. Continue removing opposite corners until the sample is the right size for the lab. Submit samples quickly.

Bacteria in the rumen are a cow's first line of defense against mycotoxins, Litherland said. They can convert most types to a less toxic form. At highest risk for mycotoxins are transition cows, with their compromised immune system, and calves, with their under-developed rumen.

Management advice

He advised producers to give cattle feed as soon as it's mixed because oxygen exposure reduces quality. Dispose of feed refusals, either by composting or feeding them to less susceptible steers. Scrape and clean feed bunks once daily. Evaluate feed intake each day on a per-pen or per-cow basis. Track changes over time, watching specifically for cyclical changes.

"If you can't measure it, you can't manage it," Litherland said.

Watch for changes in bunkers and bags. Closely monitor changes in cow health and performance such as milk yield, milk urea nitrogen, somatic cell count and changes in manure.Loose stools are a sign of mycotoxins.

Drying wet corn below 12 percent to 14 percent moisture is a good step to stop more toxins from developing. It's recommended producers use a grain inoculant to help speed up fermentation and stabilize wet corn. Litherland also suggested corn fines be removed.

He warned distiller grains could be more of a risky feed choice this year because they have the potential for higher mycotoxin levels than corn. Ethanol plants are testing for this and Litherland said it seems to be becoming less of a concern.

Producers storing corn silage in a way that exposes it to oxygenput themselves at risk for secondary fermentation of molds and wild yeasts.

Even though dairy profits are tight, Litherland suggested bringing in higher quality ingredients this year. A diversity of feed spreads out the risk of mycotoxins. This is also a good time to evaluate feed practices.

Watch results

Dairyland Laboratories, with offices in Minnesota and Wisconsin, publish test results for mold, yeast and mycotoxins on their web site, www.dairylandlabs.com. Litherland said it's difficult to get an accurate sample, and some people may have picked their samples based on which corn looked the worst, so the results may show a worst-case scenario.

"It may not be representative, but it gives us an idea of challenges out there," he said.

Of approximately 2,000 shelled corn samples tested in January, half had mold. Results also showed some yeast contamination and some vomitoxin, but not very high concentrations, as well as low levels of zearalenone. Aflatoxin, which is probably the most serious concern because it can contaminate milk and become a human health concern, was rarely found.

"That's good news," Litherland said.

In corn silage, results showed modest levels of mold but some high numbers on yeast.

"We are concerned about seeing some high yeast counts in corn silage this year," he said.