Don’t Rely on Book Values When Formulating Rations
Jul 24, 2014
The nutrient values of various feedstuffs aren’t consistent from load to load -- and that’s not easy on a cow’s rumen.
By Dr. Joel Pankowski, Manager, Field Technical Services, Arm & Hammer Animal Nutrition
The most successful rations feature ingredients that are mixed and fed properly, and are consistent in nutrient value and quality day-in and day-out. This attention to detail enhances feed intake and maximizes cow health and productivity.
However, the nutrient values—like protein, fiber and starch levels—of various feedstuffs are not consistent from load to load. The situation gets even more challenging if you do not work with the right data to make ration decisions.
Variation Occurs Often
The same variation found in forages occurs within many other commodity feedstuffs like soybean meal, dried distillers grains, cottonseed and beet pulp—not all of which are considered to be highly variable. As a result, it’s common practice to simply follow supplier guarantees for many of these ingredients.
However, assuming these values are accurate means you may be overestimating or underestimating the nutrient value of half your ration, since rations are commonly split 50/50 between forages and commodity ingredients. That assumption can lead to unnecessarily high feed cost and/or undesirable animal performance.
"What if the ingredient contributed to 100 more grams of metabolizable protein than the book value projected?" asks John Goeser, director of nutrition, research and innovation at Rock River Laboratory, Inc. "That knowledge of that difference can mean the ability to shave from 7 to 15 cents off your ration cost."
Differences in field conditions, varieties, harvesting, processing and a host of other variables mean it is unrealistic to expect commodity byproduct feed ingredients to remain constant. Still, it’s common to treat them as though their nutrient composition is unchanging when formulating rations.
Book Values a Best-Guess
It’s tempting to use book values to account for ingredient nutrient values to help average or "smooth" out some of the disparity. And while a good resource, some of the values for various commodity feeds housed in the National Research Council (NRC) database may be based on a small sample size. Or, the data used for the library may not be accurate for your region.
In 1989 researchers from the University of Missouri noted that, "Diets incorporating byproduct feeds should be evaluated carefully to avoid mineral imbalances and to maintain protein quality. Use of book values for balancing diets containing significant quantities of byproduct feeds could lead to nutritional problems, and testing should be encouraged."1
Furthermore, a 1995 survey2 of nine commodity feeds in California showed that the nutrient content of these ingredients differed by more than 20% from NRC results. Additional California studies in 2000 and 2007 featuring even more ingredients found similar nutrient variation results.
Feedstuff Variation Is Significant
Data presented by Goeser and his colleagues at the 2013 American Dairy Science Annual Meeting showed significant differences in rumen dry matter digestibility, protein bypass and substantial variation within feeds for soybean meal, canola meal, corn distillers grain, corn gluten, soy hulls and expeller meal.3
"Concentrate feed fiber content variation is just one parameter that’s not generally accounted for in dairy rations," explains Goeser. "Fiber, protein and starch levels are three parameters in these feeds that you really need to monitor to increase ration consistency and accuracy."
A 2012 study at Ohio State University illustrated that the variation in NDF among commodity feed ingredients was similar to the NDF variation found in forages. Assuming a 20% inclusion rate and average within farm variation for concentrate NDF, diet NDF could change by 0.3 to 0.8 percentage units.4
Inaccuracies Impact Performance
It’s not easy for a cow’s rumen to adapt to feed ingredient variation. As a result, suboptimal performance may occur.
For example, research5 conducted at Ohio State University last year showed that dairy cows fed a diet that contained either 7% long-chain fatty acids or 4.8% long-chain fatty acids produced less milk and had lower dry matter intake than cows fed diets with less variation.
What to Do?
While variation will always occur in forages and commodity feeds, you have options to deal with it.
The inclusion of less variable feed ingredients is one area to explore. For example, you can select an ingredient with a consistent level of dietary protein so you know more precisely what cows receive, and then deal with variability for other ration nutrients. At least you can be confident in ration protein.
Another suggestion is to adopt a routine commodity testing program similar to a testing program for your forages. While commodity feeds are not on hand as long as forages, you can compare nutrient composition of a current sample to that of the previous two truckloads to get a sense of the variability for which you must account in formulating diets.
To learn more about managing your ration to minimize variability and achieve consistent performance, visit http://www.transition.ahdairy.com/.
1 Belyea RL, Steevens BJ, Restropo RJ, Clubb AP. Variation in Composition of By-Product Feeds. J of Dairy Sci 1989;72:2339-2345.
2 Arosemena A, DePeters EJ, Fadel JG. Extent of Variability in Nutrient Composition Within Selected By-product Feedstuffs. Animal Feed Science and Technology 1995;54:103-120.
3 Goeser J, Heuer C, Meyer L. Midwestern U.S. Byproduct Feedstuffs Vary in Ruminal Nutrient Digestion. 2013;ADSA-ASAS JAM Poster TH112.
4 Weiss WP, St.-Pierre NR. Nutrient Variability in Feeds Within Farms, in Proceedings. Cornell Nutrition Conference 2012;157-166.
5 Weiss WP, Yoder P, McBeth L, Shoemaker D, St.-Pierre NR. Effect of Variation in Nutrient Composition of Diets of Lactating Dairy Cows, in Proceedings. 2013 Tri-State Dairy Nutrition Conference. Available at: http://tristatedairy.osu.edu/Proceedings%202013/William%20Weiss.pdf. Accessed June 2, 2014.