Herbicides can be used safely in areas frequented by grazing animals, as long as all available package precautions are heeded. Care should also be taken with feeding troughs, containers and implements that may be exposed to herbicides in the course of application. Herbicide toxicity information is required by law to be printed on packaging, with certain standard phrases used to indicate certain things.
Herbicides are used in areas frequented by grazing animals when weeds or other undesirable plant life has gotten out of control. In multi-pasture situations, grazing animals can be admitted to a pasture that is not currently undergoing herbicide treatment while another pasture is being treated.
Time plays an important role in herbicide safety for grazing animals. Some herbicides lose their toxicity to mammals (including grazing animals) over time. Others do not, but this information is indicated on their labels as required by law. Intervals of time between the application of herbicides and allowance of grazing animals to return to pastures varies both by herbicide product and by type of animal.
Herbicide manufacturers are required to place restricted entry intervals (REIs) on their packaging when their products are harmful to animals or humans. Signal words are also used, such as "danger/poison," which indicate that a given chemical compound can be lethal to mammals at rates ranging from as little as a few drops. Chemicals labeled "warning" are toxic at doses from 1 tsp. to 1 tbsp., while chemicals labeled "caution" are toxic from anywhere between 1 tbsp. to a pint or more.
Owners of grazing animals should keep those animals far away from pastures being treated with these chemicals until such time as it is safe for their return. Any containers for food or water for grazing animals should also be removed from areas where dangerous herbicides are being used.
Moderate herbicide exposure may result in certain symptoms in grazing animals. These symptoms include unexplained muscle tremors, seeming lack of coordination, and a marked increase in drooling. More serious herbicide exposure can result in seizures and possibly even in death. If owners notice that their grazing animals are exhibiting these symptoms, a veterinarian should be called immediately.
Herbicide labels should always be read thoroughly before use. Owners should follow their instructions to the letter, and keep all grazing animals away from herbicide treated areas and equipment until the period of danger has passed. Any package information marked "crop use information" should be heeded to the fullest extent.