By Fae Holin
Dave Combs has been traveling the U.S. the last two years, explaining the merits of total-tract NDF digestibility (TTNDFD). He says the standardized in vitro test can accurately tell how well a forage will feed.
In October, the University of Wisconsin dairy scientist added low-lignin alfalfa as part of his presentation. He and Rock River Laboratory, Watertown, WI, have been working with Alforex Seeds, which had just made public its low-lignin alfalfa, called Hi-Gest.
“What Alforex is doing with selecting a low-lignin line – TTNDFD dovetails very nicely with it – because it defines what that low-lignin level is actually doing to fiber digestibility within the plant,” Combs says.
TTNDFD, he adds, looks at fiber digestibility much the same way as producers and nutritionists look at corn starch digestion.
Farmers and consultants can get the most starch from corn by making sure their kernel processors are set up right, Combs says. “They know it means 3-5 lbs of milk production to get that starch digestibility optimized.
“The variance in fiber digestibility is twice what it is for (starch in) corn grain, so we’re missing opportunities unless we can really track that very well. We can lose 5-7 lbs of milk production if we’re not optimizing fiber digestibility,” he says.
Fiber digestibility “ranges all over the board,” Combs adds. In alfalfas, it varies from 25% to 70%; in grass hay and silages, from 15% to 80%, according to thousands of samples from Rock River Lab, analyzed over a three-year period.
“That’s why this tool, I think, will become a standard in the industry,” he says. TTNDFD incorporates three important factors that affect fiber digestion: the amount of potentially digestible fiber in a forage, how fast the fiber digests and the rate of passage from the cow.
“Those three numbers get integrated together to give us total-tract digestibility – one number,” Combs says.
Click here to see more...