Nitrates continue to be a concern for livestock producers as they deal with limited feed supplies over the fall and winter. Concentrations of nitrates can change as long as the plant is still growing and can respond to available moisture.
Fall cereal grains and cover crops - Wheat, rye, triticale and oats can accumulate nitrates. Test results have shown high nitrates this fall, and forages should not be grazed without testing for nitrates. This would include those that overwinter and might be grazed or hayed in the spring. Some of the brassicas such as turnips and radishes have had levels so high that their use for livestock feed will not be an option.
Crop residues - If an average or better grain yield was harvested, nitrates are less likely to be a problem in the crop residue left behind. However regrowth or volunteer growth in fields where grain production levels were substandard may contain problem levels of nitrate due to excess N fertilizer remaining in the soil. Sample the plant material you expect animals to graze, and in the case of fields with highly variable growth, collect separate samples that represent the different growth and maturity levels attained.
Baled forages with high nitrates - Sample each field or lot separately, because different fields or cuttings may have different nitrate levels present. The more samples you collect the better information you will have to make decisions. Nitrate concentrations tend to be highly variable within a field which can be reflected in individual bales. Storage will not decrease the nitrate concentration in baled forage.
The same sample that is used for a nitrate test can return information on protein and energy content. Corn hay baled earlier this summer is likely to be much higher in quality than corn residue baled after grain harvest. Applying the forage test information to a plan for feeding is an easy return on investment.
High nitrate feeds should be mixed with other feedstuffs to reduce the total nitrate concentration in the diet. Young, pregnant and stressed animals are more susceptible to nitrate toxicity. Make sure to consider nitrates from all components of the diet. This includes the water source. Introduce the high nitrate feed gradually over several days. Avoid situations where a large intake of high nitrate feed may occur in one meal. Over time, animals can adjust to higher levels in the diet. Feeding smaller amounts several times a day can be used to adapt cattle to nitrates. If grazing, gradually increase hours of access to the high nitrate feed.