Nitrate toxicity and the first winter snow storm

Nov 23, 2012
by WLJ

As predictable as the coming of winter will be the horror story of the death of several cows from a herd fed “the good hay” for the first time after the snow storm.

Ranchers who have harvested and stored potentially high-nitrate forages such as forage sorghums, millets, sudangrass hybrids and/or johnsongrass, need to be aware of the increased possibility of nitrate toxicity.

Of particular concern is the scenario where 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 for the first time 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 makes them even more vulnerable to nitrate toxicity.

The rancher is correct in trying to make available a higher quality forage during severe winter weather to prevent the loss of body condition due to the effect of the wind chill. But if the forage provided is potentially toxic, even the best intentions can backfire.

The best approach is to know ahead of time the concentration of nitrate in the hay. Have a representative sample of the hay tested by a reliable laboratory. If the producer is confident 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 sure-fire safe concept. If the hay is quite high in nitrate, it can still be dangerous. Diluting the high nitrate feed with other feeds can reduce (not eliminate) the likelihood of problems.

If there is no choice but to feed unknown sorghum-type hays during a snow storm, the rancher should plan to watch the cattle carefully for eight to 12 hours after feeding to be ready to remove the cattle from access to the high-nitrate forage if symptoms of nitrate toxicity appear. Nitrate toxicity causes the blood to lose its oxygen-carrying capability. Watch for cattle that are panting, staggering, disoriented, or other signs of asphyxiation. — Glenn Selk, Oklahoma State University Emeritus Extension Animal Scientist