Precautions before Grazing Alfalfa and Cover Crops
• All producers should use a bloat block and expose the cattle to the bloat block in the pasture shortly before putting them onto a cover crop or alfalfa field. Seven days prior is a good rule of thumb. The bloat blocks can be placed in their salt tub.
• Make sure the cattle are full before letting them out on to the alfalfa or cover crop.
• Test the crops and weeds for nitrates (cereal grains, kochia, turnips and radishes). Turnips and radishes seem to have the highest nitrates of the cover crops mixture. Nitrate measurements less than 1500 ppm are generally safe for all conditions and livestock. The Chouteau County Extension office has a nitrate quick test available upon request. The test does not provide a numeric measurement but gives the producer a good idea if there is nitrate in the plant.
• Prussic acid levels can be high in sorghum or sorghum/sudangrass crops, although the hazard decreases in sudangrass. Sorghums should not be grazed too early, or immediately after a frost. Any measurement below 200 ppm should not cause prussic acid poisoning.
• Test the water for nitrates, total dissolved solids (TDS), and sulfates. Nitrate less than 44 ppm is generally safe for all animals. TDS below 3000 ppm is satisfactory for most livestock. Sulfate recommendations for calves is less than 500 ppm and less than 1000 ppm for adult cattle.
• Turn cattle to only a limited area initially. Electric fence or smaller areas help cattle adapt slowly over a week or two.
• Include other portions of the pasture that do not contain nitrates. Wheat stubble without weeds, grass waterways, or pasture near watering sites allow the cattle to buffer themselves.
• Provide an energy source without non-protein Nitrogen (NPN) such as a molasses tub. The molasses will aid in nitrate reduction as it provides a carbon skeleton to combine with the Nitrate ion.
Information for this article came from Dr. Darrin Boss (Northern Agricultural Research Center Superintendent), MSU Extension Document called Nitrate Toxicity of Montana Forages (MT200205AG), and a NDSU bulletin titled Livestock and Water (AS-954).
