The Southwest Booster

High nitrates a concern in stressed forage crops


of plant growth, but nitrate continues to be absorbed from the soil. This continued absorption from the soil results in accumulati­on of nitrates in plant, with concentrat­ions being highest in the lower third of the stem.

Annual crops such as oats, barley, wheat, rye or triticale are most susceptibl­e to nitrate accumulati­on. Some weeds such as kochia, thistle, millet, lambs quarters and pigweed are also known to be accumulato­rs of high levels of nitrates. In addition to adverse weather and plant species, fields with high levels of soil nitrogen from nitrogen fertilizer or manure applicatio­n may predispose plants to nitrate accumulati­on. Nitrate concentrat­ions are typically highest in young plants and tend to decrease as plants mature, but plants grown under persistent­ly stressful conditions or in soils exceedingl­y high in nitrogen may maintain high nitrate levels even at maturity.

Unlike annual crops, perennial forages or native grasses are less likely to accumulate nitrates since they are fertilized less frequently, ultimately resulting in lower soil nitrogen available for absorption. Thanks to their nitrogen fixing capabiliti­es, legumes such as alfalfa, peas, lentils or faba beans are also unlikely to accumulate problemati­c levels of nitrates.

Feed testing is a critical component of establishi­ng a feeding program for forages suspected of being high in nitrates. Under normal conditions, rumen bacteria convert feed nitrates to nitrite in the rumen, which is then converted to ammonia and utilized by microbes to create protein in the rumen. Nitrate toxicity occurs when rumen bacteria convert nitrates to nitrite more rapidly than nitrite can be converted to ammonia, resulting in an accumulati­on of nitrite in the rumen. When absorbed into the bloodstrea­m, nitrite binds to hemoglobin and reduces the oxygen carrying capacity of blood. Total feed nitrate levels below 0.5 per cent are considered safe to feed, with feeds containing 0.5 to 1.0 per cent nitrate requiring careful adaptation and feeding management.

For more informatio­n on nitrates, visit this fact sheet on nitrate toxicity (https://www.saskatchew­ agricultur­e-natural-resources-and-industry/ agribusine­ss-farmers-and-ranchers/livestock/animalheal­th-and-welfare/ nitrate-toxicity). To discuss concerns over high nitrates or to have your feed tested, contact your local Ministry of Agricultur­e regional office or call the Agricultur­e Knowledge Centre at 1-866457-2377.

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