Quality and yield in the same hand
Higher feed intake
An increased carbohydrate content in grass will also make the feed intake increase. This is due to the improved digestibility found in high sugar grasses as well as the fact that the high sugar content “dilutes” the fibers in the plant and hence increases the amount of grass consumed. 

More milk
A higher intake of dry matter will result in an improved milk yield. Typically high sugar varieties have 2 - 3% higher dry matter digestibility compared to low sugar types. Studies have shown that an increase of 1% in digestibility gives an increase of 0,5 – 0,7 liters of milk per cow per day.

Better N-balance
With increased sugar in the grass, the balance between carbohydrates and protein in both plant and animal is more favorable. This means high utilization of protein in the animal and less nitrogen to burden the environment. 

Tetraploid varieties best
In general tetraploid varieties of perennial ryegrass have 2-3% higher carbohydrate content than diploid varieties. However there are considerable differences in both types. See diagram below - trials from 1st cut, DLF-TRIFOLIUM 2001.