By Coleen M. Jones and Jud Heinrichs
Introduction
Monitoring forage dry matter is critical to consistently feeding a balanced ration. Moisture content is the most variable aspect of forages. Other components remain relatively stable over time, but moisture can change as much as 5% from one week to the next.
This variability creates a problem because rations are formulated on a dry matter basis, but they are mixed and fed on an as-fed or wet basis. Changes in the moisture content of a forage cause changes in the amount of that forage required to provide a specific amount of protein and energy (and all the other nutrients balanced in the ration). Consider this example:
At the time the ration was formulated, the corn silage had 28.5% dry matter, 11% crude protein, and 0.67 Mcal/lb of net energy. To balance the ration, 16.8 pounds of corn silage dry matter were required. This translates to 58.9 pounds of as-fed corn silage. If the dry matter changes, but the amount fed is not adjusted, cows will be over- or underfed corn silage. As a result, the ration's protein and energy content will not meet the cows' needs. Failure to adjust feeding amounts in response to changes in forage dry matter can negatively affect cows' milk production and energy balance. On the other hand, overfeeding forages results in wasted feed, excess nutrients, and increased nutrient excretion in manure.
We recommend testing forage dry matter twice per week (instructions for using a microwave to do so are provided in the spreadsheet). The Batch Mix spreadsheet can be used to quickly adjust your ration as forage dry matter changes.
Source : psu.edu