Dairy Focus: Cows Do Not Need Corn
By J.W. Schroeder, Dairy Specialist
NDSU Extension Service
Editor’s note: This is the first article in a series on how dairy producers can lower feed costs.
Historically, attractive corn prices coupled with corn’s wide availability have led to heavy corn utilization as the main source of energy in dairy feeding programs.
In practical dairy nutrition, this has resulted in corn grain being used to maximize levels and amounts of fermentable carbohydrate that provides energy to both the rumen microbes and the dairy cow.
With the advent of higher corn prices and concurrent price increases in other grains and many byproducts, questions have been raised regarding corn use in dairy diets, and alternative feeding and ration balancing strategies, with better economic outcomes. The economic need forces the necessity to re-evaluate the role and value of carbohydrates in dairy rations, as well as ration formulation strategies to reduce feed costs.
During the High Plains Dairy Conference held in Albuquerque, N.M., late March, Normand St-Pierre of Ohio State and Joanne Knapp of Fox Hollow Consulting presented “Economics of Making Nutritional Decisions with Volatile Feed Prices.” The following is adapted from their work. Their work also will be the topic of discussion in the next three Dairy Focus articles.
Some have mistakenly equated the wide use of corn in dairy rations to a requirement for corn by the animals. This is incorrect both nutritionally and economically, as summarized by experiments where barley was substituted for corn in lactating cow rations. None of the production, composition, intake and feed efficiency parameters were affected significantly by the type of grain used. Although some small numerical differences would seem to favor corn, you must remember that these studies were designed to maximize production differences between diets based on corn or barley.
Many nutritional rules of thumb were derived during times when corn was an inexpensive feed ingredient. Some of these rules led to good working rations that were economically efficient with cheap corn. For example, some have recommended constraining dairy diets to contain 25 percent to 30 percent starch and 35 percent to 40 percent nonfiber carbohydrates (NFC). However, the experimental evidence to substantiate these recommendations is very thin.
What has been lost is that rumen microbes do not have a requirement for starch per se; the energy requirement can be satisfied by fermentable carbohydrate derived from the hydrolysis of either NFC or neutral detergent fiber (NDF). Thus, significant amounts of byproduct feeds can be used as replacements for corn without much effect on animal productivity.
Byproduct feeds can be used to replace both forages and grain in dairy cattle diets. Several research articles have been published on the ability of byproducts, such as corn gluten feed, beet pulp and soy hulls, to replace forage. Alternatively, and more importantly in this era of ethanol euphoria, byproducts also can be used to replace grains.
Byproducts are generally much lower in starch than grains, but contain significant quantities of other NFC, including sugars, organic acids, fructans, glucans and pectins. These sources of NFC are generally very degradable in the rumen and can provide energy to both the rumen microbes and the cow. Several studies have shown no decrease in rumen microbial flow to the small intestine, total tract NFC and NDF digestibilities, dry-matter intake, and milk yield and milk components when byproduct feeds are substituted for corn grain in dairy rations.
Starch contents of the diets ranged from 9.2 percent to 38.3 percent dry matter (DM), with corresponding NFC levels ranging from 27.2 percent to 50.7 percent of DM and NDF levels inversely ranging from 49.4 percent to 24.3 percent of DM. In all of these studies, forage NDF levels were maintained within or above current National Research Council recommendations for forage NDF.
According to St-Pierre and Knapp, the quadratic relationship between milk yield and dietary starch reveals a very wide range of optimal combinations and that milk production does not respond very much to dietary starch in the range of 15 percent to 40 percent of DM. The recommended 25 percent to 30 percent range for dietary starch may have resulted in good working rations in the past, but the economic penalty for this myopic view now is, as we shall see next week, excessive.
NDSU Agriculture Communication
|Source:||J.W. Schroeder, (701) 231-7663, firstname.lastname@example.org|
|Editor:||Ellen Crawford, (701) 231-5391, email@example.com|