Nonfiber carbohydrates are our best indication of the carbohydrates that are available for fermentation in the rumen. In most rations much of this fraction would be starch, primarily from grains and corn silage. Notice that the table is broken into three columns by days in milk. This corresponds to production groups similar to those in Table 1 . At the nonfiber carbohydrate levels indicated, there should be adequate energy for the rumen to produce adequate microbial protein.
Protein is divided into that which is undegradable and degradable in the rumen.
Generally, higher production warrants higher concentration of undegradable protein. Not all the research supports this idea and it is still uncertain when a response is expected. However, many nutritionists are recommending a source of rumen resistant protein in rations for high producing cows. Neither undegradable or degradable protein can be measured with a laboratory test. Therefore, book or average values are used, making this aspect of nutrition as much art as science.