These spring grasses are now setting seed heads. After the seed heads are fully set the plant will mature and go dormant until the weather cools in the fall. The flush of cool season grass growth in so rapid, and such a large amount that under normal stocking rates cattle can not consume it all. It is not until later in the summer, when the grass has slowed its growth pattern that cattle eventually are forced to graze the mature grass. This is the time frame that normally determines the carrying capacity of a cool season pasture.
Cattle are selective grazers.
They will choose the more succulent and nutritious forage first. Forage that fits this profile is typically in a vegetative stage. This is the fast growing, leafy stage. After this stage the plant will boot, sending up a seed head to flower. If the plant is cut off or grazed at this stage, or just prior to it, the plant will continue to attempt to send up a seed head.