Roughage: Effective Fibers
by James I. Sprague, Nutritionist
Feed Analysis: CF, ADF, NDF
Evaluating roughages in feedlot rations is a mixture of applied science and practical experience by cattle feeders and their advisors. Randy Royal, manager of the Servi-Tech Laboratories, said the “younger nutritionists” that submit samples to their laboratories are now increasingly requesting neutral detergent fiber (NDF) for evaluating roughages. Acid detergent fiber (ADF) is also tested and is used in the energy equations.
Crude fiber (CF) is still tested extensively even though it has a major short coming in evaluating feedstuffs, but it has a large basis of experience and can be used with judgment for ration and feedstuff evaluation.
Roughage in rations
Certainly it depends if roughage feeds are used in an all roughage ration for wintering cows, compared to grow ration with part roughage, and if used in high grain finishing rations. And now, rations with grain distiller’s products or gluten feeds may need less roughage. Certainly roughage is used at a higher level in starter rations than finish rations. Nutrition advisors and feeders reduce the high fiber ingredients in steps from 50-70 percent in starter rations down to 8 to 12 percent. And even in some cases, no roughage in whole corn finishing rations was used.
I personally used a column for “R” factor. For example, I used 100 percent “R” factor for “field chopped” alfalfa hay, while only 80 to 90 percent for “tub ground” alfalfa hay. But for corn silage a value of 50-70 percent was used, depending on the estimate of the grain content of the silage. This value of “R factors” helped to develop the sequence from starting to finish rations.
Effective NDF (eNDF)
One of the latest ideas to help evaluate rations is the idea of “effective fiber” by evaluating the analysis of neutral detergent fiber (NDF). Dr. Rodney Preston suggested this system and added this category to his feed analysis table as published each year.
The question remains, how much roughage is required in cattle finishing ratios? Preston suggests that a calculated level of eNDF may be from 5 to 20 percent in a finish ration depending on the level of feed-bunk management, feed grinding, chopping, or flaking, plus the effect of fine grinding of the roughage. Feedyard managers and nutritionists work out the practical aspects of ration formulation which includes many factors other than roughage level. The advisors assign eNDF values for the ingredients of their clients, based on analysis and practical observation. Certainly the eNDF system of evaluating roughage feed is a more scientific method, but still does not replace the practical approach that many feedlot nutritionists are using now.