Since fiber is bulky it is retained in the rumen where the cellulose and hemicellulose are fermented slowly. As plants mature, the lignin content of fiber increases and the extent of cellulose and hemicellulose fermentation in the rumen decreases. Fiber in the form of long particles is essential to stimulate rumination.
Rumination enhances the breakdown and fermentation of fiber.
It stimulates ruminal contraction, and it increases the flow of saliva to the rumen. Non-fibrous carbohydrates increase the energy density of a diet, which improves the energy supply and determines the amount of bacterial protein produced in the rumen. However, non-fibrous carbohydrates do not stimulate rumination or saliva production and, in excess, they may impede fiber fermentation. Thus, the balance between fibrous and non-fibrous carbohydrates is important in feeding dairy cows for efficient milk production. Figure 1 summarizes the transformation of carbohydrates in various organs.