As drought ravages grassland, pasture, hay fields, and grain crops, ranchers are working hard to find immediate feed sources and source feed for the winter.
Grazing or haying drought-affected fields requires navigating the issues of fencing, crop insurance considerations, payment, and more, but there’s also feed quality to consider. For some ranchers, sourcing feed low in nitrates could prove challenging, given how widespread the drought conditions reach.
According to the Saskatchewan Ministry of Agriculture, nitrate poisoning occurs when plants grow under stressful conditions, such as drought or a frost event. It happens when the normal plant function of taking in nitrate and converting it to ammonia is interrupted and nitrate levels build up in the plant.
“Under normal conditions, cattle convert the nitrate in forage to nitrite which is then converted to ammonia and used by microbes in the rumen to make protein. When nitrate levels are elevated, however, the nitrate converts to nitrite faster than nitrite converts to ammonia in the rumen. When this occurs, nitrite accumulates and is absorbed into the bloodstream where it binds to hemoglobin, thus reducing the oxygen-carrying capacity of the blood and animals die by asphyxiation,” according to a fact sheet by Saskatchewan Agriculture.
But how much nitrate is too much? The toxic level depends both on the amount of nitrate in the feed and how fast that feed is consumed. For example, it takes about twice as much nitrate to kill a ruminant when the nitrate comes from forages that are eaten over a long period, and have been gradually introduced, as compared to a feed that is consumed quickly and to which the animals have not been previously exposed.
Many crops can accumulate nitrates, including oats, canola, barley, and wheat.
One of the key management points is to first test silage and green feed, and yes, even dry hay. Feed high in nitrate can be safely fed over time, but it will require an adaptation period and a slow introduction to the ration.
There are several labs that will perform a nitrate test. You can find the listing here.