Grasses, even when dormant, are fair to good sources of energy for ruminant animals, but other nutrients, especially crude protein and carotene, are likely deficient when plants are dormant. If only cool-season species are present, these species are the most nutritious during spring and possibly again during late summer or fall if regrowth occurs. There usually is a period during midsummer when cool-season grasses are less palatable because of stemmy reproductive structures and older leaf material. On the other hand, a pasture that contains primarily warm-season grasses does not provide very nutritious forage in early spring, because these grasses grow better during late spring through midsummer. For example, you may want to establish cool-season grasses in tame pastures to use in early spring or fall when these species are most nutritious.
Livestock can rotate to pastures with warm-season species during late spring and summer.
If you use crested wheatgrass, Russian wildrye, bromegrass, or winter wheat for early-season pastures, move animals to native rangelands during late spring and summer. Because of cooler temperatures in the mountains and shorter growing seasons, cool-season species adapt best to these conditions. Range ecologists and physiologists have found that as grazing increases, grass productivity typically declines. Frequency can be more important than intensity. A plant that is harvested often has more photosynthetic tissue removed and little opportunity for regrowth.