Extension of the grazing season by 2 months (56 to 64 days) by the addition of spring and fall complementary pastures of introduced domesticated grasses to a summer grazed native grassland pasture showed improved livestock weight performance.
Grazing forage grasses is more efficient and effective when the phenological growth stages, the herbage production curves, and the nutrient quality curves of the forage sources match the biological and physiological requirements of the grazing livestock. This action of coordination between the primary producers and the primary consumers is called “seasonality”.
All of the perennial forage grasses growing in the Northern Plains region have growth characteristics that can be categorized into three seasonality units.
The spring unit can be 28 or 32 days long during early to late May includes the introduced domesticated cool season grasses, like crested wheatgrass and smooth bromegrass.
The summer unit can be 135 to 137 days long during early June to mid October includes the cool season and warm season native grasses; no introduced domesticated grasses are qualified for the summer unit.
The fall unit can be 28 to 32 days long during mid October to mid November includes all of the wildryes, like Altai and Russian wildrye. The fall unit can also include spring seeded winter cereal grasses, like winter rye. The total combination grazing period can be 191 to 201 days long during early May to mid November.
There are no perennial grasses that can grow in the Northern Plains that qualify biologically for grazing during mid November to late April. This nongrazing period can be 164 to 174 days long.
Scientists from the Swift Current Research Branch in southwestern Saskatchewan and the NDSU Dickinson Research Extension Center in western North Dakota have worked extensively on the development of complementary grazing systems based on the seasonality concept for the Northern Plains. Initially, both research centers used a simple three pasture system with crested wheatgrass, native grassland, and Russian wildrye, and both research centers have also worked with Altai wildrye as the fall pasture.
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