High-nitrate forage? Handle with care, not fear

Excessive nitrate levels in annual forages are a serious concern. Livestock consuming high-nitrate forages can suffer from nitrate toxicity, which, in acute cases, can lead to death. This issue is widespread, costly and can develop quickly under certain conditions. 

Some plants, especially brassicas, are particularly prone to nitrate accumulation, but small grains and cover crop mixes are also at risk. Environmental stressors such as drought, cold weather, cloudy days, shortened sunlight hours and high soil nitrogen levels all increase the chances of nitrate buildup.

Fortunately, nitrate toxicity is largely preventable. While lab tests often reveal high nitrate values in plants, grazing cattle are less likely to experience poisoning than the numbers might suggest. This is because grazing conditions differ from feeding dried hay. Green forages release nitrate into the rumen more slowly than hay does, and fresh forage is consumed over a longer period, spreading out the nitrate intake. 

A principal factor is that cattle tend to graze selectively, leaving the stems behind. When we take forage samples for testing, we collect a representative portion of the entire plant, including stems. However, in practice, cattle usually eat the more palatable parts of the plant, avoiding the lower stalk or stem where nitrate concentrations are highest. Additionally, many annual forages, such as brassicas and immature grasses, are high-energy feeds, and cattle on these diets can handle greater nitrate levels.

Testing forage is always a good precaution if you suspect high nitrate concentrations. In general, hay made from high-nitrate forages poses the greatest risk. Silage, on the other hand, tends to be safer because much of the nitrate is lost as silo gas during fermentation, although toxicity problems can still occur.

If you plan to use high-nitrate forage, a few management strategies can help minimize the risk. It’s important not to turn hungry cattle out onto forage that may have high nitrate levels. Filling them up on hay first can reduce the risk. Providing a supplement like Cattle Charge with Rumensin and Shield Technology can also help support their performance and rumen function.

Choosing the right cattle for high-nitrate forage is another key consideration. If only a fraction of the herd needs to utilize the high-nitrate feed, feedlot steers are the safest candidates, followed by open cows and growing calves. These animals are most tolerant. Stockers and unbred replacement heifers are a little more vulnerable, while pregnant cows are at the highest risk and should be the group you are least likely to feed these forages.

When introducing high-nitrate forage, do so gradually. Ideally, start cattle on forage with lower nitrate levels and slowly increase the concentration over time, giving their systems time to adjust.

If possible, allow cattle some selective grazing, feeding to a 10% to 15% refusal. This allows them to avoid the more dangerous lower stalks and focus on the parts of the plant that are lower in nitrate concentration. 

Finally, when adapting cattle to lower-quality, high-nitrate forages such as pearl millet or mature sorghum-sudangrass, it can be helpful to provide extra energy supplements like Cattle Charge with Rumensin and Shield Technology to support the rumen microbes. This encourages the conversion of nitrate into bacterial protein rather than toxic nitrite.

With careful testing, management and feeding practices, high-nitrate forages can still be a valuable resource without putting your cattle at risk. Talk with your MFA solutions provider for more information.