Unfortunately, NFC is a non-uniform fraction. Portions of the NFC ferment faster than other portions. Because of this non-uniformity, NFC can ferment very differently depending its ingredient source. Beta-glucans, galactans, and pectins, also referred to as soluble fiber , must be fermented in the rumen since starch enzymes in the intestine cannot break them down.
Soluble fiber is fermented rapidly but yields a weaker acid called acetic acid, as a by-product.
Thus, soluble fiber generally does not lower rumen pH and cause acidosis. For this reason, starch digestibility, both in the rumen and intestine, has a crucial impact on milk production. Cereal grains, such as corn and barley, provide the greatest proportion of the starch in a cow's diet. Starch is made up of units of a sugar, called glucose, which are bonded together. Depending on the starch source and processing, the glucose units may be very tightly bonded and compacted together or they may be weakly linked together.