“When changing forages, watch the direction of the NDFd change – going from lower to higher means more forage can probably be fed and energy gained,” he says. “Dropping to a lower category would have the potential to reduce DMI, lower energy consumption from forage and force you to reduce the proportion of forage in the ration.”
If ration NDFd is lower than expected, Rymph recommends taking out the feedstuffs with the lowest NDFd, usually haylage, and replace that NDF with NDF from feeds that have a higher NDFd such as corn silage, soy hulls, beet pulp or corn gluten feed.
Conversely, if a ration has a very high NDFd consider replacing some of the highly digestible feedstuffs with a lower NDFd feed ingredient, such as straw or haylage to maintain a stable rumen mat and ensure cud chewing.
“Traditionally, we have tried to compensate for low quality/digestibility forages by feeding more grain - typically high starch grain like corn. We often over-fed starch, reducing fiber digestibility in the rumen even more,” he says. “With new starch testing technologies like Calibrate® Technology from Forage Genetics International, 7-hr in vitro starch digestibility and the University of Wisconsin Grain System (version 2) available, we should be able to more precisely balance the sugar and starch in the ration and avoid some of problems we saw in the past.”
Once the digestible NDF in the ration has been optimized and starch has been safely maximized, any remaining calories required will likely have to come from fat. “Fat is an important component to maximizing high NDF forages because it helps us moderate starch levels while still increasing energy density of the ration,” says Rymph.
For more information, contact Dr. Stuart Rymph at (608) 469-8538 or email: firstname.lastname@example.org.
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