Boosting corn silage levels in rations has proved to be a great strategy for pushing dairy heifer weights at calving to 1,300 lbs or more and age at first calving to 24 months or less.

But the strategy carries a downside, too. With more heifers being reared in confinement and eating high-energy rations with corn as the base ingredient, they've overall been getting fatter. That can lead to problems like dystocia and metabolic disorders at calving, and can also reduce milk production over the animal's lifespan.

A possible solution: Growing long-season corn hybrids that don't make ears. University of Wisconsin researchers have completed two years of studies with several varieties of long-season hybrids developed in Brazil, Mexico and south Texas.

“The whole idea is that, if the long-season hybrids don't make ears, you end up with low starch and energy and the heifers won't get so fat,” says Zen Miller, extension dairy and livestock agent in Outagamie County.

In the studies, hybrids were planted at several locations in late April to early May at plant populations fairly typical for Wisconsin farms. The corn tasseled in late September (about six weeks to two months later than normal) and was harvested in October and November.

“A few of the varieties did develop some ears of various sizes, but most did not,” reports Mike Rankin, extension crops and soils agent in Fond du Lac County.

Among the general findings:

  • Yields in the test/demonstration fields were a mixed bag, says Rankin. “In some locations, they were comparable to the conventional hybrids. But in other plots, they were significantly lower. It's been a little hard to sort out.”

  • With all the hybrids, crude protein content was a little higher than normal.

  • Starch content for several of the hybrids was less than 10%. With traditional corn silage hybrids, starch is usually in the 25-35% range.

  • The TDN value was less than 63% in several hybrids. “At that level, you don't need to put a cutter into the ration to reduce overall energy content,” says Miller. “It would give producers a little more flexibility to bring economic ingredients like distillers grain into the ration.”

  • NDF percentages ranged from the mid-30s to low 60s.

Miller believes several factors could limit Midwestern dairy producers and custom heifer raisers from adopting the long-season, earless concept. Waiting so long for the corn to dry down in fall could lead to mycotoxin problems. Also, an early season snowstorm could disrupt harvest.

“If you don't like to be the last one chopping in your area, this probably isn't for you,” says Miller. “On the other hand, custom harvesters might like it because they'd have a little more flexibility on scheduling.”

He also notes that the hybrids in the study grew to a height of about 12-13'.

“Overall, standability was pretty good,” he says. “We thought we might see some problems at harvest with corn flipping over or having trouble pulling it into the chopper. But for the most part, we found that if you throttle back a little bit, everything turns out alright.”

Rankin points to seed availability as another possible issue. “We ran into some problems getting enough seed just to do the studies,” he says. “And it's relatively expensive.”

Even so, he believes the concept has merit. “If we can get a high-yielding forage with low starch content, it would have a niche in the marketplace. But there's more work to be done. It's not quite ready for prime time.”