Wild Yeasts, Shredlage Hot Topics at Virginia Silage Conference

12/15/2012 7:00 AM
By Jane W. Graham Virginia Correspondent

WYTHEVILLE, Va. — There is no place for complacency in silage production, a University of Delaware silage specialist told farmers gathered at the Hobert N. Grubb Building here Dec. 7.

Limin Kung Jr., a professor in the university’s Dairy Nutrition and Silage Fermentation Laboratory, was among the speakers at “Making Your Corn Silage Count,” a conference sponsored by the Virginia Forage and Grassland Council and Virginia Cooperative Extension.

The conference also was held Dec. 5 in Dayton and Dec. 6 in Rocky Mount.

Kung spoke on “Hot Topics in the World of Silages,” including wild yeasts, shredlage, microbial inoculants, ensiling time and volatile compounds

He put a lot of emphasis on wild yeasts that get into silage and cause problems. In fact, he called them the vampire bats of silage.

“In the U.S., it is generally accepted that lactate-assimilating yeasts initiate aerobic spoilage in silage,” Kung wrote in the proceedings of the meetings. “Measurements from commercial labs and from research studies have shown that numbers of total yeasts in spoiling silages can be as high as 109 colony-forming units per gram of silage.”

He cited research that added high concentrations of a spoilage yeast isolated from silage to in vitro ruminal fermentations. This reduced the neutral detergent fiber digestibility of a TMR in a dose-dependent fashion, he said.

“The fact that yeasts may have negative impacts on rumen fermentation have also been reported by Chung et al., (2011) who found that the addition of yeast from an experimental direct-fed microbial formulation resulted in a more acidic rumen when fed to dry cows,” Kung wrote. “More research is needed to determine if consumption of high number of yeasts from spoiled silage have negative effects on animal performance.”

Yeasts need air to do their damage, Kung said. Yeasts don’t need water as they assimilate lactate acid turning it into carbon dioxide and water. This affects the dry matter for cows, and if cows don’t get dry matter they cannot make milk.

Kung also discussed shredlage, a new way of making silage in which the corn is shredded rather than chopped. He said the shredded material which is longer than chopped corn seems to be a more effective fiber and has the potential of being more digestible. Choppers have been modified and research is under way on animal performance, packing density, processing scores and sorting, he said.

Kung suggested fresh corn may be low in starch digestibility and that adding exogenous proteases to fresh corn plants when making silage may increase in vitro ruminal starch digestibility faster that that naturally occurring in untreated silage.

Producers adding liquid microbial inoculants need to pay attention to the temperature in their tanks, Kung stressed. When the temperatures get above 100 degrees F, they can lower the effectiveness of the inoculants, he said, adding the water can be cooled by putting a one-liter plastic bottle of frozen water in the tank as needed.

Kung also addressed volatile organic compounds.

“Volatile organic compounds (VOC) add to global warming,” he wrote. “Research has identified silages as the primary source of VOC from dairy farms with ethanol being a major contributor to the problem (Malkina et al., 2011) More emphasis is being placed on determining how to control the emissions of VOC from silages.

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