Farmers across the country are dealing with high grain prices. A University of Illinois Extension Specialist explains some feeding alternatives and signals to monitor when decreasing starch in the ration.
Extension Dairy Specialist
University of Illinois, Urbana
Shelled corn prices continue to climb as ethanol production uses corn grain as a fuel source. The challenge (the “3F functions”) for future corn uses will be:
- •food for human consumption and use
- •fuel for transportation
- •feed for livestock
Livestock managers may need to adjust rations as role of corn grain slips to the third function. Questions raised by dairy farmers are being asked below.
How much corn grain is needed in the dairy ration?
The key guideline is the needed level of fermentable carbohydrate (starch, sugar, and soluble fiber) in the total ration dry matter to optimize rumen microbial growth and provide a glucose source in the small intestine. Current recommendations are 18 to 26 percent total starch (including cereal grains and corn silage), 4 to 6 percent sugar, and 10 to 12 percent soluble fiber. High quality forage and use of by-product feeds can reduce the level of starch needed, but monitor cow performance carefully.
How can I increase starch availability?
Starch availability from corn silage will increase the longer it is stored. In March, corn silage starch will be more available than in December due to “cooking” rendering it more soluble in the silage juices. Kernel processing of corn silage will make the grain more digestible, especially if the corn silage was harvested over 35 percent dry matter.
Corn grain can be made more available if dry corn is ground to 1100 micron size, corn is roasted or steam-flaked, or stored as high moisture corn (28 to 32 percent dry matter). These processes will gelatinize the starch, increase surfaced area, and/or increase availability of starch leading to greater fermentability in the rumen. To determine if your dry corn averages 1100 micron, take a cup of your ground corn and sift through a baker or kitchen flour sifter. If 2/3 of the grain passes through screen, it is about 1100 microns.
By optimizing starch particle size, fecal starch levels can drop (below 10 percent) and increase starch availability (“stealing” starch from manure). The risk with smaller corn particle size is that ration adjustments must be made otherwise allowing more starch in the rumen that could lead to rumen acidosis.
What feeds can be substituted for shelled corn?
Cereal grains (such as barley and wheat) could replace corn, but normally these grains are more expensive than corn on a starch equivalent base. Bakery waste will vary in starch content depending on its source (cookies or bread). Increasing corn silage levels replacing legume and grass forage sources will increase starch intake. Wheat midds and corn gluten feed contain small levels of starch. Adding sugar (total of 4 to 6 percent in the total ration dry matter) can replace some starch. Increasing fermentable or soluble fiber (beet pulp, citrus pulp, soy hulls, or corn bran) can compliment lower starch levels as a source of rumen fermentable carbohydrate.
Will shifting to distillers’ grain for shelled corn work?
Corn distillers’ grains are higher in protein, oil, and fiber, but low in starch. Substituting corn distillers for corn will not achieve comparable results if starch levels are currently balanced. Consult with your nutritionist before replacing corn grain with distillers.
What should I monitor if I “cheat” the level of starch down?
Lowering starch levels could work on dairy farms if the level of starch was high initially. Dairy managers can experiment by shifting levels and feed ingredients. “The cow is always right” is a theory, so watch for these signals that you have cheated starch levels too low.
- •Milk production could decline due to less rumen volatile fatty production by rumen microbes.
- •Milk protein test could drop due to lower microbial protein yield.
- •MUN (milk urea nitrogen) may increase as less ammonia is captured by microbes in the rumen.
- •Manure may become stiffer as more undigested fiber can appear in feces.