Almost as predictable as the coming of the winter season is the horror story of the death of several cows from a herd fed "the good hay" for the first time after a snowstorm. Ranchers who 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, says Glen Selk, Oklahoma State University Extension cattle specialist.
That's especially true if the cows are fed this hay for the first time after a severe winter storm.
"Cattle can adapt (to a limited amount) to nitrate intake over time. However, cattlemen often will feed the higher quality forage sorghum type hays during a stressful, cold, wet winter storm," Selk says. Cows may be especially hungry, because they haven't grazed 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 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 backfire."
The best approach is to know ahead of time the concentration of nitrate in the hay. If the producer is confident the hay is very low in nitrate content, then the hay should be safe.
If 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 isn't a foolproof concept," Selk says. "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."
If the rancher has no choice but to feed unknown sorghum-type hays during a snowstorm, watch the cattle carefully for 8-12 hours after feeding to be ready to call the veterinarian for the antidote to nitrate toxicity, if cattle start to show signs of asphyxiation and going down.
-- Cow-Calf Corner Newsletter