For many years the standard recommendation among nutritionists, including DuPont Pioneer forage specialists, has been to wait until after Christmas to feed new-crop silage. Recently, researchers discovered the rationale behind this decades-old recommendation, says Bill Seglar, DuPont Pioneer dairy nutritionist and veterinarian.
It starts with the physiology of the corn kernel and changing rates of starch digestion (often referred to as the mathematical term, Kd). Concentrations of zein proteins, which encase starch granules in the kernel's endosperm, increase with kernel maturation and peak at the time of black-layer formation. To preserve the next generation, these storage proteins were created with the ability to repel water to prevent premature starch hydration that could set off early germination.
These zein proteins inhibit starch availability and present a nutritional challenge. However, over time in fermented storage, silage microbial activity and the chemical action of fermentation acids gradually solubilize zein proteins freeing up starch granules for more rapid digestion by rumen microbes. As the corn kernels in corn silage begin fermentation, they undergo the most rapid changes during the first two to three months in storage. It has been proven in animal trials in both the U.S. and Europe that the rate of starch digestibility (Kd) is also changing rapidly over this period, providing scientific basis for the long-held recommendation to wait to feed new-crop silages.
Time-course studies with lab-scale research silos indicate that corn silage starch digestibility plateaus after about five to six months in storage. This finding is further supported by monitoring average protein solubility in corn silage samples submitted to commercial laboratories. If feed inventories allow, it's best to wait two to three months after harvest before feeding new crop corn silage.
By doing this, you will avoid the rapid changes in feed that make consistent nutrition levels an impossibility. Having enough silage on hand to allow for longer waiting periods before feeding new-crop is an economic decision based on the inventory carrying cost of that feed. However, it appears that most rapid changes will have abated within the first two to three months.
For more information about new corn silage feeding tips, visit http://www.pioneer.com/silagezone or contact your local DuPont Pioneer dairy specialist or livestock information manager.