March 22, 2022
Dickinson Research Extension Center Updates
Management that can reduce mineral deficiencies
Llewellyn L. Manske PhD
Scientist of Rangeland Research
North Dakota State University
Dickinson Research Extension Center

Spring complementary crested wheatgrass pastures should contain a fair amount of standing dead vegetation to slow down the rate of forage passage through the digestive tract of livestock. Management
practices that remove most of the standing dead vegetation has the potential to cause serious mineral deficiencies in the grazing cows blood. 
 
Mature lactating cows can develop milk fever or grass tentany while grazing lush spring crested wheatgrass vegetation that contains little standing dead grass. Milk fever is caused by a blood deficiency of calcium (Ca) and grass tetany is caused by a blood deficiency of magnesium (Mg). 
 
Crested wheatgrass herbage, however, is rarely deficient in calcium or magnesium during the growing season. A cows blood serum deficiency of calcium or magnesium is not caused by consuming crested wheatgrass forage deficient in these minerals. 
 
Absorption of most essential minerals is by passive diffusion across the intestinal wall; some calcium is transported by a protein carrier.  Only about half of the ingested minerals are absorbed through the intestinal wall into the cows blood system under normal conditions. 
 
During the early spring, the rate of forage passage through the cows digestive tract is accelerated when the lush vegetation high in water and crude protein is consumed; greatly reducing the quantity of dietary minerals absorbed through the intestinal wall and potentially resulting in deficiencies of calcium or magnesium in the cows blood. 
 
Cattle grazing crested wheatgrass pastures containing sufficient amounts of dry standing carryover residual vegetation can maintain normal slow rates of forage passage through the digestive tract and normal rates of mineral absorption; which in effect, prevents the occurrence of mineral deficiencies in the blood and thus preventing the development of milk fever or grass tetany in cows grazing crested wheatgrass spring (May) complementary pastures.
 
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