The key to stimulating a rapid increase in rumen microbe numbers is the supply of energy in the form of quickly degradable carbohydrates i.e. soluble sugars. Digestion of these sugars stimulates the rumen fermentation process. Carbohydrate sources comprised of starch and fibre are slower to digest and are less effective.
Sugars in the diet increase the overall rate of feed digestion and boost dry matter intakes.
The Metabolisable Energy [ME] value of a feed is the sum of the energy contributions from its sugars, starch and fibre content. When sugars are lacking, energy supply is unbalanced and feed will not perform to its potential.