Vet Notes - Toxic Grazing

Dr Josh Beutler presents monthly Vet Notes

Things continue to remain dry for a large portion of the Midwest and Plains regions. Some areas have received relief but, for the most part, many people are abnormally dry. Drought can cause plenty of problems, and as we transition into winter and grazing cover crops, there are a few key things to monitor with drought-stressed forages.

Nitrate toxicity

One of the biggest concerns is nitrate toxicity. Clinical signs of nitrate toxicity are sudden death, respiratory distress and weak or down cattle. Lower levels of toxicity may not affect the cow clinically but can still cause fetal abortion and defects.

There are a few things that I recommend if you are concerned about this.

  1. Visit with your local veterinarian. He or she can offer herd-specific tips and grazing techniques. They are also capable of sending off samples for testing to measure toxicity levels. Nutritionists are also a good resource to discuss nitrate toxicity and can be reached through your state Extension agents. 
  2. Turn out cows on corn stalks or other forage while they’re full. You can also provide hay for the first week or two so that they can slowly adjust to the toxicity.
  3. Provide a good protein source such as tubs, cubes, and other options, which will help provide more energy and reduce toxicity production.
  4. Remove cattle off corn stalks or forages sooner than normal. Most nitrate accumulation occurs in the bottom third of the stalk; thus, the husks and leaves tend to be lower in nitrates. Cows eat the husks and leaves before they resort to eating the stalk. We can remove them before they have high levels of exposure if we monitor them closely. It is worth noting that the energy and feed value of a stalk is fairly poor in general, so it is beneficial to remove cattle in non-drought-stressed years as well.
  5. Fence off severe drought-stressed areas such as pivot corners, where the nitrates are more likely to be severe.

Grazing stalks

Remember these five tips for grazing corn stalk residue.

  1. Do not overgraze if cattle are behind in energy and feed levels during late gestation. It greatly affects the calf in utero as well as colostrum quality. It also subsequently affects the calf’s performance. The rule of thumb I recommend is to figure a cow per acre for 30 days on a field that yields 150 bushels per acre. If you have 100 acres, it could essentially run 50 cows for 60 days. This can vary based on the yields (better yield = more grazing days per acre), but this is the easiest way to figure your grazing levels to keep your cows in a good condition.  Again, it is time to move when leaves and husks are gone.
  2. Make sure cows are in good condition going to stalks. First-calf heifers and thin cows may need extra protein or feed to help get them into a more positive energy balance and to put on appropriate condition to handle winter and maintain calf development in utero and post-calving.
  3. Provide a mineral supplementation especially heavy in vitamin A. The weak and stillborn calves I see in my practice are most commonly due to deficient vitamin A. Winter forages tend to be low in vitamin A and affect the calves if not supplemented.  

There are multiple mineral options available, and your local feed store or nutritionist should be able to help you find the appropriate mineral supplement. That provides you trace minerals needed. 

If you have any other questions, your local veterinarian is typically more than willing to help you set up a winter grazing plan to help ensure you have healthy cows that develop healthy calves.


About the Author: Dr. Josh Beutler graduated from Iowa State University with a degree in veterinary medicine, before moving to Pender, Nebraska, where he practices in a five-person, two-clinic practice. He practices mostly beef production medicine with cow-calf and feedlot operations throughout northeast Nebraska. Beutler also works closely with his family on a fourth-generation SimAngus cow-calf herd.

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