Bank on corn silage in your rations
What was once considered a high corn silage diet is not high compared to today’s standards. We commonly feed diets containing at least 80 percent of the forage dry matter (DM) from corn silage.
One of the biggest reasons for this change is consistency. It is much easier to put up one good, consistent crop of corn silage than it is to put up three to five consistent crops of haylage.
Herd growth has also helped to elevate the amount of corn silage in diets. Economics push us to harvest the greatest amount of DM per acre. It is especially important when herds expand and their land base doesn’t grow equally. Corn silage is our highest yielding forage. It typically yields at least 8 tons DM per acre while alfalfa yields struggle to get 5 tons DM.
More carryover needed
Nutritionists want as much carryover corn silage as possible, but a realistic recommendation is to maintain enough carryover to feed the previous year’s corn silage until January or February.
Why? In the past, we thought fiber digestibility improved as corn silage sat in storage. We now know fiber digestibility changes very little from the day corn silage was chopped and stored. However, starch digestibility improves as corn silage sits. Click here for more details on this topic.
We can realistically lose an average of 6 pounds of milk from October through December when feeding new crop corn silage in a high corn silage diet. When using a $20-per-hundredweight milk price, that is a loss of $54,900 on a 500-cow dairy. Carrying three to four months of extra silage inventory does add cost, but it is less than the lost milk and cow health issues we see when feeding new corn silage.
However, factors like weather and expansion can deplete carryover. Several alternatives related to starch digestibility can help in situations of low carryover:
- Excellent processing: Expanding surface area by pulverizing kernels will help improve digestibility and minimize the starch passing through the cow.
- Short-day corn varieties: These can be chopped early to sit for one month before feeding. They will usually be chopped slightly immature, so protein and starch linkages in the kernel will have less time to form.
- High-digestibility corn varieties: These varieties have more floury starch than vitreous starch. Floury starch contains fewer starch and protein linkages.
Ensure effective fiber
Often, the biggest concern we have with high corn silage diets is ensuring enough effective fiber. This fiber slows rate of passage, stimulates cud chewing, and improves rumen fermentation and digestion.
Although many challenges result from lower starch digestibility, we can also have issues with very fast starch digestibility. It can cause a rapid drop in rumen pH, potentially leading to depressed milkfat synthesis. Nutritionists may need to adjust the amount of starch, type of starch sources, and ingredients high in unsaturated fatty acids, such as distillers grains.
Feeding little or no haylage can result in low potassium diets, which is why we feed straw with corn silage in many of our close-up cow diets. Doing so helps prevent milk fever.
However, we want higher levels of potassium in milk cow diets. Research indicates higher levels of potassium may improve milk production and milkfat synthesis. Liquid feed ingredients like delactose permeate, whey permeate, and molasses fit well in high corn silage diets, not only as sugar sources, but also because they are fairly high in potassium.
Corn silage contains up to 40 percent starch on a DM basis, so less corn grain has to be fed, making more space in the diet for protein. The other benefit is that less expensive protein sources containing more rumen degradable protein (corn gluten feed, canola meal, soybean meal) and urea can be fed instead of more expensive rumen undegradable proteins (RUP) sources (blood meal, heat-treated soy products, etc.).
Finally, we can rely on the rumen to produce more microbial protein to support milk production rather than forcing more expensive RUP sources to the lower gut. When you add in the fact that it costs less to produce corn silage than alfalfa haylage, high corn silage diets become more economical than higher alfalfa-based diets.
This article was originally written for the October 25, 2014 issue of Hoard’s Dairyman.
About the author: Dr. Darin Bremmer grew up on a farm in Shannon, Illinois. After high school, he attended the University of Wisconsin-Platteville and received a bachelor’s degree in animal science in 1993. From 1993 to 1995, he attended the University of Illinois and received a master’s in animal science with an emphasis in ruminant nutrition. Bremmer then completed a Ph.D. in nutritional sciences with an emphasis in animal nutrition and a minor in dairy science from UW-Madison in December 1999. In Dr. Grummer’s laboratory at UW-Madison, Bremmer’s research focused on transition cows, studying ketosis and fatty liver. After completing his Ph.D., Bremmer worked for a major feed company as a dairy nutritionist and technical services manager in Wisconsin. In March 2003, he joined Vita Plus as part of the dairy nutrition and technical services team based in central Wisconsin.
Feed quality and nutrition