Producers need to be mindful of forages as frosty weather continues to creep in.
As plants grow, they take in nitrogen from the ground. When a forage freezes, the plant continues taking in nitrogen, but because growth is slowed, nitrates accumulate. If the forage is cut and fed to livestock with high nitrates, it can cause nitrate poisoning by starving the animal of oxygen.
John McGregor, extension support person for Manitoba Forage and Grassland Association, says in the case of a light frost, a frozen plant will use up the excess nitrates when it thaws and continues growing, so it will go back to being relatively safe to feed.
But things get a little different when the temperature dips down to about minus two.
"If we get a hard frost on plants, if you cut it early, you may not have as much nitrates accumulate in the plant itself, so there's the potential to reduce the amount of nitrates," says McGregor. "Or if you don't have that opportunity and you cut the plants with the high nitrates in it, if you get your plants tested at a feed lab, what you can do is determine the level of nitrates in the plant, and therefore you can dilute the nitrates by feeding other non-nitrate-type forages so that you can get it down to a safe level for the animals."
Source : PortageOnline