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Corn Breeding Project Aims For Super Silage

Not surprisingly, farmers in America”s Dairyland grow more corn for silage than any other state in the nation. Wisconsin”s annual silage crop is worth about $150 million. Surprisingly, there hasn”t been much research on the feeding value of corn for silage, until recently.

The University of Wisconsin Maize Breeding Project is the only public breeding/genetics program in the nation working on corn silage, according to Jim Coors, a corn breeder at the College of Agricultural and Life Sciences. Since 1991, the project has coordinated a large-scale survey of commercial and experimental breeding germplasm, concentrating on intake potential and digestibility.

“There is genetic variation for nutritive value among adapted U.S. corn hybrids with both silage yield and grain yield potential,” Coors says. “Forage quality and agronomic traits are not highly correlated and it should be possible, through routine screening, to identify productive hybrids with improved intake potential and higher protein and digestibility.

“The bulk of U.S. corn breeding has been for grain; silage has always been a second use of corn,” Coors says. “Then you have years like 1996, when the corn crop may not mature for grain and will be chopped for silage. We want to know if there are hybrids that are best for silage. Many high-yielding grain hybrids have been bred in this century. Do they vary significantly in quality? If they do, then farmers need to know which are best, and which could be the best dual-purpose grain/silage hybrid,” he says.

Project scientists have examined more than 350 hybrids, inbred lines and breeding populations in order to establish the range of quality attributes. The research team includes a corn breeder, agronomist, forage physiologist and dairy nutritionist.

The CALS researchers look for three silage quality parameters: protein content, intake potential and digestibility. They have found that hybrids vary significantly in composition and digestibility, both for stover and whole-plant samples. Many seed companies now test their corn for silage potential, Coors notes.

He thinks we can make good hybrids better in terms of quality. “Genetically, corn is very variable, and there is a lot of room to play around,” he says. “Our studies of potential inbred parental lines and other experimental germplasm show that breeders might be able to increase digestibility by several percentage points by merely including more digestible germplasm into breeding programs.”

Coors has the only research program looking at the potential silage quality of inbreds — all the other programs go for grain yields, he notes. Most of the inbreds in his nursery fields are runty little plants dwarfed by the 7-foot tall hybrids in adjacent plots. Coors inbreeds corn by self-pollinating plants for six generations to get a “finished inbred,” which is crossed with another finished inbred to produce a hybrid.

A quick tour of the corn nursery plots at the West Madison Agricultural Research Station reveals a medley of corn varieties:

The “lax” inbred, which looks wilted because it has less fiber and lignin in its leaves. The lower fiber content gives it better silage possibilities.-
Potential grazing corn ? a short plant that grows in a clump due to its grassy tiller, and grows back after grazing.

Corn with the brown midrib gene. This corn has low lignin in its stover, which could produce silage with less fiber and higher digestibility. A hybrid combining low lignin and grassy tiller could be a great grazing corn, Coors notes.

South American germplasm inbreds.

Coors also works with the Germplasm Enhancement of Maize project ? a public/private research effort to strengthen U.S. corn hybrids by rescuing and using irreplaceable Latin American germplasm.

Much of this exotic germplasm has been selected for food, beverages or forage by various cultures for thousands of years, Coors points out. He is looking for value-added traits, including nutritionally superior GEM germplasm that will improve the feeding efficiency of corn silage.

Corn hybrids in the United States have a very narrow genetic base, using just 5 percent of all available corn germplasm. This greatly increases vulnerability to disease and pest problems, and may lead to an eventual yield cap, Coors points out. Exotic corn germplasm could provide genes for resistance to pest problems and for increased yields. These exotic materials may also contain quality traits to meet new market demands.