Perennial cool season grasses can also be of very high quality. For example, Smooth Brome grass harvested when seed heads are half emerged can test upwards of 16% crude protein and 61% TDN. Other cool season grasses such as Orchard grass, Intermediate and Pubescent Wheat grasses can contain similar protein and TDN levels when harvested at late boot to early head emergence growth stage.
It is possible to harvest forages that test high enough in crude protein and energy to meet a cows requirement even during lactation. For example, a 1300 lb. mature cow with 20 lbs. peak milk will require a diet that contains 10% crude protein and 60% TDN. A 1,100 pound heifer 40 days after calving will require a ration containing 11% crude protein and 62% TDN (these ration requirements come from the Nutrient Requirements of Beef Cattle (http://books.nap.edu/catalog.php?record_id=9791).
When forages are cut early to obtain higher quality some yield will be lost in quantity, however, the trials that Dr. Volesky conducted clearly show that acceptable yields can be obtained even when harvesting early to capture very high quality forage.
Forages containing over 8% crude protein and 53% TDN are adequate for maintenance of dry pregnant cows. If the forage tests over these values, then the cows will gain weight (body condition) when fed these higher quality forages.
Source: University of Nebraska