Increasing corn prices and lowering milk prices are causing dairy producers to think twice about what they feed their cows this spring.

"Dairy farmers can't afford to take cows off feed now because it takes too long to bring them back into full production," said Mike Hutjens, University of Illinois professor of animal sciences emeritus.

"The good news is that dairy cattle have an advantage because they can utilize forages and byproduct feeds. The bad news is that the price of corn increases the price of alternatives as well."

Alternative feedstuffs such as distillers grains, corn gluten, fuzzy cottonseed, alfalfa and hay may not be corn, but they are all in the same market, Hutjens added. As nutrient prices go up in starch and energy, it drives the other prices up as well.

"Producers need to look at how much corn they should be feeding," Hutjens said. "For a dairy cow, 24 to 26 percent starch is the typical level. Producers can get that from hominy, corn silage or shelled corn. So the question becomes what are the more economical sources available at the farm?"

As prices go up, sugar becomes an alternative that can feed rumen bacteria (target 4 to 6 percent in the total ration dry matter). Another source is soluble fiber, or fiber that the rumen microbes can break down in the rumen (target 10 to 12 percent in the total ration dry matter).

"The bottom line that our producers need to realize is that you can't cheat the bacteria — they don't read the farm magazines and know the price of corn went up to $7.60," Hutjens said. "They just know they need certain carbon structures in the rumen to produce. We never want to slow them down. As a result, they produce 80 percent of the cow's energy and 60 percent of her amino acids. Make sure rumen microbes are maxed out even if the price of corn appears to be high."