A Box Elder County rancher lost 24 cows to a poisonous weed, the Box Elder County Sheriff's Office said.
Det. Cordell Thompson said laboratory tests on the animals, completed earlier this week, determined they died after eating halogeten, an invasive weed common throughout the West. Thompson said the rancher had recently relocated the cows from Idaho to grazing land in Promontory. They had been grazing the land for about a week when they began to sicken and die.
Halogeten is extremely toxic for sheep, which can die within an hour after eating the plant, according to a Utah State University website on noxious weeds. Cattle are also susceptible but don't die as quickly and can actually tolerate the plant if they are exposed to it gradually.
Thompson said the rancher reported each animal was valued at between $1,300 and $1,400. They were not insured.
According to the USU website, the weed was once believed to have been "introduced by Russian spy planes as a biological weapon during the Cold War."
But it's more likely that accidental seed contamination was the cause. Since it was first detected in 1934 in Nevada, the plant has invaded millions of acres in the West.