Most of the hay produced for beef cows in Tennessee comes from tall fescue fields. There are, however, a significant number of producers that use summer annual grasses like sorghum x sudangrass hybrids and pearl millet for hay. These plants can be used successfully for hay production. But there is the potential for a buildup of nitrates in these plants, especially during a drought like we had this summer. It is important for producers to get some assistance determining the nitrate levels in any summer annual hay produced this summer.
Nitrate poisoning occurs when animals consume hay containing high levels of free nitrates.
Under drought conditions, both sorghum X sudangrass hybrids and pearl millet have the potential to accumulate high levels of nitrates, especially if they have been fertilized with nitrogen. Feeding hay that was cut during or just after a drought should be avoided. Nitrate accumulation occurs because the plant continues to take up nitrogen through the roots, but drought conditions cause an inadequate water supply for rapid plant growth. Nitrates are accumulated in the plant for use in protein formation when adequate water becomes available. When the animal consumes a plant with high nitrate levels, the nitrogen is converted from nitrate to a form called nitrite.