Corn is the cornerstone of modern forage and feeding systems. Whether grown for silage, grain, high-moisture corn, or stover, corn often represents the largest single contributor of energy, starch, and dry matter in dairy and beef rations. Yet despite its central role, corn is frequently treated as a ‘known quantity’, meaning that it is assumed to be consistent, predictable, and interchangeable from field to field or year to year. In reality, however, corn is anything but uniform. Weather patterns, soil fertility, hybrid selection, harvest timing, storage conditions, and processing methods all influence nutrient composition and digestibility. Small differences in starch availability, fiber digestibility, or nitrogen status can translate into meaningful impacts on animal performance, feed efficiency, and farm profitability. As a result, testing corn at multiple stages and in multiple forms is no longer optional, but rather a strategic tool for agronomic decision-making, ration formulation, and risk management. This article explores how and why to test corn, beginning with nitrogen status in the field, moving into silage analysis for ration building, and expanding to other corn-based feeds that deserve attention.
Building a Ration with Corn Silage
Corn silage testing is an essential part of building a nutritionally balanced total mixed ration. Corn silage is one of the most important feeds used in the dairy and beef cattle industries, providing both energy and fiber in a single forage. This fermented livestock feed is made from the entire corn plant harvested while still green and moist. This includes the stalk, leaves, husk, cob, and grain – everything! This nutritional powerhouse contains a complex blend of nutritional components including starch, fiber, protein, and fermentation products. Its nutritional value varies widely depending on variety or hybrid, maturity at harvest, kernel processing, and storage conditions. Relying on book values or historical averages can lead to inaccurate ration formulation. Even small deviations in starch digestibility or fiber content can shift energy supply enough to affect milk production, growth rates, or feed efficiency. A comprehensive corn silage analysis typically includes dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), starch, water soluble carbohydrates (WSC), ethanol soluble carbohydrates (ESC), fat, ash, fermentation acids (lactic, acetic, butyric), and pH, as well as in vitro fiber digestibility (e.g., NDFD) and starch digestibility.
To use corn silage in the most efficient way, it is important to understand its main nutritional components. For example, corn silage provides energy primarily as starch from the grain and digestible fiber from the plant. The balance between these sources determines how silage performs in a ration. High starch silage supports high milk production but may increase rumen acidosis risk if not balanced properly. High fiber digestibility supports intake and rumen health but may require supplemental starch. Testing allows nutritionists to quantify these components rather than guessing.
Total starch content tells only part of the story, however. Two silages with identical starch percentages can have very different ruminal availability depending on several factors, including the kernel processing score, vitreousness of the endosperm, hybrid genetics, and storage time and fermentation. Advanced analyses such as undigested neutral detergent fiber on an organic matter basis (uNDFom) and starch digestibility tests provide insight into how much starch is actually available to the animal. This information is critical for optimizing rumen fermentation and maximizing feed efficiency. In addition, neutral detergent fiber digestibility (NDFD) influences dry matter intake and energy extraction. Higher NDFD generally correlates with greater intake and improved performance. Testing for NDFD allows nutritionists to predict intake potential, adjust forage-to-concentrate ratios, evaluate hybrid performance, and compare silages from different fields or harvest dates. Fermentation acids (i.e., lactic acid, acetic acid, butyric acid, etc.) and pH reveal how well the silage was preserved. Poor fermentation can lead to reduced palatability, dry matter losses, increased spoilage, and health challenges in animals. Moreover, routine fermentation analysis helps identify issues early and supports better storage and management practices.
While laboratory analysis provides a snapshot of nutrient composition, it is also important to recognize that corn silage is a dynamic feed. Nutrient availability changes throughout storage and feedout as fermentation progresses and environmental conditions fluctuate. For example, starch digestibility often increases during storage as the protein matrix surrounding starch granules breaks down, improving rumen accessibility. Likewise, improper feedout management can increase spoilage losses and reduce the nutritional value actually delivered to livestock. Regular testing throughout the feeding season helps ensure ration adjustments reflect current forage quality rather than relying on outdated harvest data. Ultimately, corn silage testing is only valuable if results are translated into actionable ration adjustments. Whether by adjusting grain supplementation based on starch content and digestibility, modifying protein sources based on crude protein levels, balancing fiber sources to maintain rumen health, or fine-tuning mineral supplementation based on ash content. In high-performing herds, incremental improvements in ration precision can yield substantial economic returns. Corn silage analysis is the foundation of that precision.
Stay tuned for the next issue to learn more about other forms of corn and why to test them!