Editor's note: The following article appeared in the July 2014 issue of Dairy Herd Management.
Cows crave consistency in routine and nutrition. The most successful rations are mixed and fed properly and consistent in nutrient value and quality, enhancing feed intake and maximizing cow health and productivity. However, consistency can be difficult when you consider feedstuff nutrient values — like protein, fiber and starch levels — are not consistent from load to load. The goal gets even murkier if you do not work with the right data to make ration decisions.
1) Nutritional variation is common
The same variation found in forages occurs within many other commodity feeds like soybean meal, dried distillers grains, cottonseed and beet pulp. 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 100 more grams of metabolizable protein than a book value projected?” asked 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 and processing make it 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.
“Variability is real,” said Goeser. “Not many will argue that it’s not. But we haven’t always had practical ways to measure the nutritive value of commodity feed ingredients.”
2) Book values are a best-guess
It’s tempting to use book values to account for ingredient nutrient values. But, while a good resource, some of the values 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.
3) Variation among feedstuffs is significant
The compelling reasons to monitor and account for feed ingredient variation continue to add up. For instance, data presented by Goeser and his colleagues at the 2013 American Dairy Science Annual Meeting showed significant differences in rumen dry matter digestibility, bypass protein and substantial variation within feeds for soybean meal, canola meal, corn distillers grain, corn gluten, soy hulls and expeller meal.