If you want to lessen your cows from participating in the annual event known as the new crop corn silage slump, take action to prevent it. Testing for rumen digestibility of starch and fiber when you open the bunker, and every two weeks while feeding, can help you take control.
Corn silage is highly variable, says Dr. David Weakley, director of dairy forage research for Calibrate® Technologies. Crude starch, rumen degradable starch, neutral detergent fiber (NDF) and NDF digestibility can vary from year to year, from field to field and hybrid to hybrid.
Results from a sampling program in Texas show just how variable things can be. “We tested 300 fresh cut corn silage samples from a handful of Texas producers,” says Dr. Weakley. “Samples were taken from 12 different corn silage hybrids. Results showed crude starch varied from 22.8 percent to 46.1 percent. NDF ranged from 30 percent to 67.6 percent.” Calibrate’s rapid NIR test was used to determine digestibility values for those 300 corn silage samples.
The results in Texas are similar to what is seen every year across the country in corn silage samples. Corn silage contains a lot of variation; not only at harvest, but it continues to change during ensiling until fed to the cows, explains Dr. Weakley. The longer corn silage is ensiled the more digestible the starch becomes. “That means by the time spring rolls around, if you haven’t adjusted the ration to account for the increase in starch availability in the corn silage, cow performance can suffer,” he says. “Generally, when starch availability climbs above optimal levels in the diet; the butterfat content of milk drops.”
One way to manage this variation and minimize its influence on cow performance is to test for rumen digestibility of starch and fiber every two weeks. Doing so provides insight into how the cows will perform. For example, the amount of rumen degradable starch tells you how much energy the cows can extract from the starch and how it will be used. NDF digestibility provides insight into rumen fill, how quickly feedstuffs pass through the rumen and dry matter intake; all of which are helpful information to minimize variation in the cows’ diet and subsequent performance.
Regular testing of the rumen digestibility of starch and fiber alerts you to changes in the corn silage before cow performance suffers. That means you can reformulate the diet and maintain cow performance. Digestibility testing also can help you improve feed efficiency, formulate a more cost-effective ration, and diagnose milk composition problems.
Digestibility testing is a tool. Use it to gain insight into your corn silage. Then put that insight to work to accomplish the production and performance goals for your herd.