Diet Deep Dive: Will Starch be in Short Supply?

Hands shelling corn ( Darrell Smith )

After a gruesome corn silage harvest season plagued with wet weather, an early frost and even snow in some parts of the country, farmers are now starting to feel some of the pressure lift from their shoulders. While corn might be off the field, the battle isn’t necessarily over. Tough conditions mean cow diets could be lacking one major component: Starch.

“In the old days, nutritionists used to recommend that silage be harvested at 30% to 32% dry matter, or 68% to 70% moisture,” says Bill Mahanna, global nutritional sciences manager for Pioneer. “This corn silage dry matter range would correspond to a milk line about a third of the way down the kernel.”

The deposition of starch within the kernel is what dries down the plant, Mahanna explains. However, deposition of starch was hard to accomplish this year because planting was so late in many areas that the plants were still somewhat immature when producers started harvest to get ahead of average killing frost dates. 

“Growing degree days were harder to come by towards the end of the growing season, making it tough for the plant to finish starch deposition,” he says.

With starch harder to come by this past season, producers might see nutritional loss racking up their feed bills. 

“You can always add starch to the diet,” Mahanna says. “However, adding that starch back into the diet comes with a cost.” 

In a more normal year, starch can be optimized by allowing the kernel to reach a minimum of ¾ milk line before harvesting, Mahanna explains. If the plant is still relatively green and healthy, Mahanna suggests that harvesting the plants at ¾ milk line will correspond to a dry matter closer to 36%-38%.

Research shows that with modern corn genetics and improved late-season plant health, fiber digestibility will remain relatively flat, thus allowing farmers to harvest at a more mature kernel milk line. 

“Once the milk line starts to decline, a healthy corn plant can lay down as much as 1% point of starch for every two days in remains in the field,” Mahanna says. “It takes about two weeks in the Midwest for the plant to go from a from a one-third milk line to a three-quarter milk line, but that could gain us up to seven points more starch in the silage. So, you need to ask yourself this question: ‘Do you want to go from say 32% starch to maybe 39% starch if the growing season and hybrid maturity will allow for delaying harvest?’ Think what that could do to your ration cost if you could grow the starch rather than having to purchase it.”