Drought-stressed sorghum and/or corn are the source of most of the forage-related cases of nitrate poisoning in Kentucky, but wheat, sudangrass, rye, pearl millet, soybeans, beets, Brassica spp. (rape, kale, turnips, swedes) and oats can also accumulate nitrates. Common weeds that are nitrate accumulators include ragweed, pigweed, thistle, bindweed, dock, jimsonweed, and johnsongrass.
Few plants normally contain high nitrate levels, since under normal growing conditions the nitrates are converted to protein as quickly as they are absorbed from the roots. However, under certain conditions such as high nitrogen fertilization, drought or abrupt changes in weather, plants can develop dangerously high nitrate levels. The main problem with excess nitrates is that they are converted in the rumen to nitrites that are absorbed in the bloodstream and ultimately prevent the red blood cells from carrying life-giving oxygen. Death or abortion may result as a consequence of nitrate intoxication. Care must be taken to recognize possible toxic forages and manage them appropriately to avoid animal loss. The laboratory you intend to use or your local county agent can provide specific instructions for nitrate testing.
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