Educators often speak of “a teachable moment.” Sometimes the most lasting lessons are painful to learn. The predicted blast of winter weather for this week may provide another teachable moment for cow calf producers in the Southern Plains.
Almost as predictable as the coming of the winter season, will be the quickly spread horror story of the death of several cows from a herd that was fed "the good hay" for the first time after a winter storm. Ranchers that have harvested and stored potentially high nitrate forages such as forage sorghums, millets, sudangrass hybrids, and/or johnsongrass, need to be aware (not fearful) of the increased possibility of nitrate toxicity. This is especially true if the cows are fed this hay for the first time after a severe winter storm.
Cattle can adapt (to a limited extent) to nitrate intake over time. However, cattlemen often will feed the higher quality forage sorghum type hays during a stressful, cold, wet winter storm. Cows may be especially hungry, because they have not gone out in the pasture grazing during the storm. They may be stressed and slightly weakened by the cold, wet conditions. This combination of events make them even more vulnerable to nitrate toxicity.
The rancher is correct in trying to make available a higher quality forage during severe winter weather in an effort to lessen the loss of body weight and body condition due to the effect of the wind chill. But if the forage he provides to the cows is potentially toxic, his best intentions can back fire.
The best approach would be to know ahead of time the concentration of nitrate in the hay. Contact your local County OSU Extension office about hay sampling details. The OSU Soil, Water, and Forage Analytical Lab can test the hay for nitrate content. If the producer is confident that the hay is very low in nitrate content then use of the hay should be safe. If the nitrate content is unknown, then precautions should be taken. Feeding small amounts of the hay along with other grass hays during the fall and early winter days can help to "adapt" the cattle to the potential of nitrate. This is not a fool-proof concept. If the hay is quite high in nitrate, it can still be quite dangerous. Diluting the high nitrate feed with other feeds can reduce the likelihood of problems.